This application is the U.S. national phase entry of PCT/IB2011/000753 with an international filing date of Mar. 10, 2011 for APPARATUS AND METHOD FOR PRODUCING A FIBROUS PRODUCT, the entire disclosure of which is fully incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates generally to a fibrous product and an apparatus and method for producing a fibrous product. In particular, the fibrous product may be an acoustical and/or thermal insulation product such as a pipe insulator. 
     BACKGROUND 
     Fibrous products are used for numerous industrial purposes, such as for making insulation products, structural products, reinforcement products, decorative products, etc. Insulation products include thermal insulation products, which block heat flow, and acoustical insulation products which can have either a sound-barrier quality to block the transmission of sound or a sound-absorptive quality to dissipate or absorb sound, or both a sound-barrier quality and a sound-absorptive quality. Examples of fibrous thermal and/or acoustical insulation products, are pipe insulators used to prevent heat and/or sound passage from the inside of the pipe to the surrounding air. Such pipe insulators may be used, for instance, in a muffler of an automobile exhaust system. Typically, pipe insulators are hollow tubular fibrous products made from glass wool. 
     One method for manufacturing a pipe insulator from glass wool comprises the following steps: manufacturing a tape of glass wool containing a binder; folding the tape into a tubular shape (by bringing the longitudinal edges of the tape into contact with each other) by means of a folding shoe through which the tape is passed, thereby forming a tube of glass wool; and advancing the tube through a mold while passing hot curing gases through the tube to cure the binder, thereby forming the pipe insulator. Typically, the glass wool tape is folded around a central mandrel, this mandrel being perforated for the passage of the hot curing gases. Such a method is disclosed, for instance, in U.S. Pat. No. 4,564,486 and U.S. Pat. No. 6,319,444. 
     One drawback of this method is that folding the glass wool tape into a tubular shape having a cross-section different from a circular one, may be difficult. Another drawback is that bringing and bonding the longitudinal edges of the tape together may be difficult and creates a bonding interface between these longitudinal edges, such an interface affecting the overall insulation properties of the pipe insulator. 
     Another method, disclosed in U.S. Pat. No. 4,569,471, comprises the following steps: providing a container consisting of an outer cylinder, a perforated inner tube and a first end cap; blowing glass wool with compressed air into the container, for filling the container with the glass wool, while sucking the air out of the inside of the container by means of a suction fan, via the perforations of the inner tube; and welding a second end cap on the container. 
     One drawback of this other method is that the glass wool has a natural tendency to expand and come out of the container (even when suction is applied) and, therefore, the glass wool often spreads over and soils the welding area for the second end cap. 
     Thus, there remains a need in the art for additional methods of producing fibrous products. 
     SUMMARY 
     According to one aspect of the present disclosure, there is provided a method for producing a fibrous product. Such a method comprises: 
     passing a texturized yarn through a first passage having a first outlet; 
     projecting the texturized yarn from the first outlet, inside a chamber delimited by a first surface, so as to fill the chamber with the texturized yarn, thereby forming a first segment of the fibrous product; 
     moving the first segment away from the first outlet, along a first axis; and 
     forming a second segment of the fibrous product in place of the first segment and contiguously to the first segment, as many segments as necessary being contiguously formed by repeating the above steps. 
     Such a method allows one to produce easily a fibrous product having a cross-section which may be constant and different from a circular one. More particularly, it allows one to produce easily a fibrous product with an asymmetrical cross section, a hollow cross section with multiple holes, a U-type cross-section, an annular cross-section with a slit in the cross-section, or any other suitable cross-section. 
     Also, with such a method, the segments of the fibrous product may be continuously formed and, therefore, the fibrous product may be continuously and rapidly produced. 
     It is to be noted that one or several texturized yarns may be passed and projected simultaneously from the first outlet. 
     It is also to be noted that the segmentation of the fibrous product may be merely a mental construction, said segments resulting from a mental discretization of the fibrous product. 
     In certain embodiments, the first surface, which delimits the chamber, extends substantially parallel to the first axis. 
     In certain embodiments, the chamber has a constant cross-section. 
     In certain embodiments, the first outlet rotates around the first axis, the texturized yarn being projected from the rotating first outlet. The first outlet may, for instance, rotate 360 degrees around the first axis or may have an oscillatory rotating movement around the first axis. 
     In certain embodiments, the segments of the fibrous product are continuously formed, the texturized yarn being continuously projected from the first outlet and the segments being continuously moved away from the outlet. Thus, the fibrous product may be continuously and rapidly produced and there is no discontinuity in the structure of the fibrous product, especially between two contiguous segments. 
     In certain embodiments, the first surface is defined, at least partially, by at least one moving band which moves relative to the first outlet, the segments being moved away from the outlet by the moving band. The segments may be moved by friction with the moving band and/or by projections (e.g. needles or pins) carried by the moving band, these projections penetrating into the segments and dragging them away from the outlet. 
     In certain embodiments, the moving band passes through a folding shoe configured to wrap the moving band around the first axis. Thus, the moving band may define, partially or totally, the first surface delimiting the chamber. 
     In certain embodiments, suction is applied through at least a portion of the first surface so as to draw gas out of the inside of the chamber. This allows the gas used for projecting the texturized yarn, to be drawn out of the inside of the chamber. Moreover, suction draws the texturized yarn towards the first surface, thereby improving the contact between the texturized yarn and the first surface. When the first surface is defined by the moving band, and when the segments are moved away from the outlet by the moving band, applying suction through the moving band improves the friction between the segments and the moving band and, thus, makes the driving of the segments by the moving band easier. 
     In certain embodiments, the produced fibrous product is a hollow tubular product, and the chamber has a constant annular cross-section being delimited, outwardly, by the first surface and, inwardly, by at least one second surface extending substantially parallel to the first axis. The first surface delimits the outer surface of the hollow tubular product, whereas the second surface(s) delimit(s) the inner surface(s). There may be one, two or more second surfaces and, thus, one, two or more corresponding holes through the hollow tubular product. The second surface may be the outer surface of a shaft. 
     In certain embodiments, the second surface is defined by a shaft (i.e. the outer surface of the shaft) extending axially along a second axis which is parallel or merged with the first axis. The second surface (so, the shaft) may rotate around the second axis. The second surface may be a cylindrical surface and, more particularly, a cylindrical surface of revolution. 
     The rotating motion of the second surface around the second axis, may be continuous or discontinuous. In the latter case, the second surface rotates around the second axis, then stops, rotates again, etc. The rotating direction around the second axis may be different before and after a stop of the rotating motion. In addition, the velocity of rotation may be constant or varying. The rotating motion of the second surface avoids the texturized yarn to stick on this second surface. 
     In certain embodiments, the texturized yarn is formed by passing a multifilament yarn through a texturizing nozzle. Such a nozzle separates and entangles the filaments of the multifilament yarn, so that the yarn is texturized when emerging from the nozzle. 
     In certain embodiments, the texturized yarn is a continuous yarn. A continuous texturized yarn has the advantage of incorporating filaments (or fibers) so long (compared to their diameters) that they can be considered to be essentially unending. The long nature of the filaments substantially decreases the amount of free filaments that can become dislodged from the product, even under extreme service conditions. This may be interesting when using the fibrous product as a muffler in an automobile exhaust system. 
     Otherwise, the texturized yarn may be a chopped yarn. The texturization may occur before or after chopping. In the latter case, post chop texturizing may be done, for instance, by feeding the chopped yarn down a texturizing nozzle with a tube where the friction between the filaments and the tube walls allows the yarn to be texturized by rubbing the filaments off the yarn. The chopped texturized yarns emerging from the texturizing nozzle may be drawn into the first passage by an air educator. 
     In certain embodiments, a binder is added to the yarn and the binder is cured on the segments. The binder may be added to the yarn at any time, i.e. before or after the texturizing step and, if after, before or after forming the segments. 
     According to another aspect of the present disclosure, there is provided an apparatus for producing a fibrous product, the apparatus comprising: a first passage through which a texturized yarn is passed, the first passage having a first outlet; a first chamber delimited by a first surface; a projection system for projecting the texturized yarn from the first outlet into the first chamber, the first chamber being filled with the projected texturized yarn so as to form a first segment of the fibrous product; and a conveying system for moving the first segment away from the first outlet, along a first axis, thereby allowing a second segment to be formed in place of the first segment and contiguously to the first segment. 
     In certain embodiments, the first surface extends substantially parallel to the first axis. 
     In certain embodiments, the chamber has a constant cross-section. 
     In certain embodiments, the first outlet rotates around the first axis, the texturized yarn being projected from the rotating first outlet. The first outlet may rotate 360° or less, it may rotate continuously or discontinuously, and it may rotate always in the same direction or not. 
     In certain embodiments, the conveying system comprises at least one moving band which moves relative to the outlet, the first surface being defined, at least partially, by the moving band. In one example, the conveying system comprises a conveyor belt forming the moving band, this belt being driven by rolls. In another example, the conveying system comprises a limited length of fabric/tissue driven by a winder at the discharge side of the system. 
     In certain embodiments, the apparatus comprises a folding shoe through which the moving band passes, the folding shoe being configured to wrap the moving band around the first axis. 
     In certain embodiments, the apparatus comprises a suction device for applying suction through the first surface, so as to draw gas (usually air) out of the inside of the chamber. 
     In certain embodiments, the fibrous product is a hollow tubular product and the first chamber has a constant annular cross-section which is delimited, outwardly, by the first surface and, inwardly, by at least one second surface extending substantially parallel to the first axis. 
     In certain embodiments, at least one shaft extends axially along a second axis which is parallel to the first axis, the second surface(s) being defined by the shaft(s) (i.e. the outer surface(s) of the shaft(s)). The shaft(s) may rotate, continuously or discontinuously, around the second axis. 
     In certain embodiments, the apparatus comprises a texturizing nozzle for passing a multifilament yarn therethrough, in order to form the texturized yarn. 
     In certain embodiments, the apparatus comprises a binder injector for adding a binder to the texturized yarn, and a curing unit for curing the binder on the segments. For instance, the outlet of the binder injector may be located near the first outlet of the first passage, so that binder is applied to the texturized yarn emerging from the first passage. 
     In certain embodiments, the curing unit has a curing chamber and the curing chamber is adjacent to and located downstream from the first chamber. The first chamber may be integrated in the curing unit, which has the advantage (among others) of improving the apparatus compactness. 
     With the above method and apparatus, any kind of fibrous product may be produced, including more particularly: fibrous products having good acoustical and/or thermal insulation properties, such as pipe insulators; fibrous products having good filtration properties, such as gas or liquid filtration cartridges; or fibrous products used as catalytic converters. 
     According to another aspect of the present disclosure, there is provided a fibrous product of constant cross section, extending along a first axis, the fibrous product comprising a texturized yarn forming curls, these curls being superimposed while being shifted with respect to one another along a shift line, this shift line being substantially a helical line around the first axis. The helical line may extend axially along the entire axial length of the fibrous product, or only along a portion of this axial length. The texturized yarn may be a continuous texturized yarn. 
     Said curls are obtained by projecting the texturized yarn from said first outlet with a projection speed much higher than the rotating speed of the first outlet and the axial moving speed of said segments. 
     Such a fibrous product has good homogeneity and other interesting properties, such as good acoustical and thermal insulation properties. It may be used as a pipe insulator. 
     Other features and advantages of the proposed method, apparatus and product, will be apparent from the following detailed description referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference signs generally refer to the same parts throughout the different views. The drawings are diagrammatic and not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
         FIG. 1  is a sectional view of an example of an apparatus for producing a fibrous product of constant cross-section. 
         FIG. 2  is a perspective view showing the moving band and the curing unit of the apparatus of  FIG. 1 , the moving band passing through the curing unit. 
         FIG. 3  is a cross-sectional view of the fibrous product produced with the apparatus of  FIG. 1 . 
         FIGS. 4 to 9  are cross-sectional views, like that of  FIG. 3 , of fibrous products which may be produced with other apparatuses according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, it is referred to the accompanying drawings showing an example of apparatus according to the present disclosure. It is intended that this example be considered as illustrative only, the scope of the invention not being limited to this example. 
     The apparatus  1  of  FIG. 1  is for producing a fibrous product  100  of constant cross-section, this cross-section being shown in  FIG. 3 . 
     In the present disclosure, “upstream” and “downstream” are defined relative to the normal flow direction of the yarn and segments through the apparatus. 
     The apparatus  1  comprises, from upstream to downstream:
     a texturizing nozzle  8 ,   a rotating nozzle  13  with a first internal passage  12 , the first passage  12  having a first outlet  14 ,   a binder injector  55 ,   a first chamber  20 ,   a curing unit  52 , and   a circular saw  60 .   

     The texturizing nozzle  8  is fed with a multifilament yarn  6  made of glass filaments or fibers. This nozzle  8  is a conventional texturizing nozzle using compressed air for advancing the yarn  6  through the nozzle  8  and projecting the yarn out of the nozzle  8 . The air which is blown through the nozzle  8  both imparts a forward movement to the yarn  6  and blow apart and entangle the filaments so that a texturized yarn  10  (i.e. a kind of “wool sausage”) emerges from the outlet of the nozzle  8 . The outlet of the nozzle  8  is located in front of the inlet of the first passage  12 , so that the texturized yarn  10  is projected into the first passage  12 . It is to be noted that the outlet of the nozzle  8  might also be located within the first passage  12 . 
     Then, the texturized yarn  10  passes through the first passage  12 , emerges from the first outlet  14  of the first passage  12 , and is projected from the first outlet  14  into the first chamber  20  which is to be filled with the projected texturized yarn  10 . The texturizing nozzle  8  is an example of projection system according to the present disclosure. Other suitable projecting systems include, but are not limited to, air blowers or air educators. 
     By filling the chamber  20  with the texturized yarn  10 , a first segment  31  of the fibrous product is formed inside the chamber  20 . The chamber  20  is of constant cross-section and is delimited by a first surface extending substantially parallel to a first axis A. The first segment  31 , whose shape is delimited by the chamber  20 , has a constant cross-section and a surface (here, its outer surface) which extends substantially parallel to the first axis A. 
     The apparatus  1  further comprises a conveying system for moving the first segment  31  away from the first outlet  14 , thereby allowing a second segment  32  to be formed in place of and contiguously to the first segment  31 . Thus, in  FIG. 1 , the first segment  31  is represented downward from the second segment  32 . The conveying system comprises a moving band  40  which moves downstream relative to the first outlet  14 . 
     Referring to  FIG. 2 , the conveying system comprises a conveyor belt  41  forming the moving band  40 , the belt  41  being driven by rolls  43 . The moving band  40  passes through a folding shoe  42  configured to wrap the moving band  40  around the first axis A. In this example, the folding shoe  42  is located upstream from the chamber  20 , the chamber  20  being integrated in the curing unit  52 . In other examples, the folding shoe is also integrated in the curing unit  52 . 
     The apparatus  1  further comprises a shaft  26 , or mandrel, extending axially along the first axis A. The outer surface of the shaft  26  extends substantially parallel to the first axis A and defines a “second surface” according to the present disclosure. 
     The rotating nozzle  13  revolves together with the shaft  26 . In other examples, the rotating nozzle  13  and the shaft  26  may revolve independently from each other. 
     More particularly, the rotating nozzle  13  forms part of the shaft  26 . That is, the first passage  12  is formed inside the shaft  26 , the first passage  12  opening out into the upstream end face of the shaft  26 , and into the outer (lateral) surface of the shaft  26 . Therefore, the inlet of the first passage  12  is located on the upstream end face of the shaft  26  and the outlet of the first passage  12  is located on the outer surface of the shaft  26 . Such a configuration improves the compactness of the apparatus. 
     In order to further improve the compactness of the apparatus, the nozzle  8  may be integrated in the rotating nozzle  13 . 
     The shaft  26  is driven in rotation by a power train  27  with a driving belt  28 . The shaft  26  may rotate, continuously or discontinuously, around the axis A and it may rotate 360° or not, depending mainly on the desired motion of the first outlet  14 . 
     The segments  31 ,  32  of the fibrous product  100  are continuously formed, the texturized yarn  10  being continuously projected from the first outlet  14  and the segments  31 ,  32  being continuously moved away from the outlet  14 , along the axis A, by the moving band  40 . Accordingly, there is no concrete dividing interface between the segments  31 ,  32 , and the fibrous product  100  has a continuous structure along its (axial) length. 
     The apparatus  1  further comprises a suction device  25  for applying suction through the first surface  22  of the chamber  20 . Here, the first surface  22  being defined by the moving band  40 , suction is applied through the moving band  40  by a sucking box surrounding the moving band  40 . In this example, the suction device  25  is integrated in the curing unit  52 , at the entrance thereof. The suction device  25  allows the gas used for projecting the yarn  14  (here, air), to be drawn out of the inside of the chamber  20 . The amount of drawn gas being greater than the amount of incoming gas, low pressure is created inside the chamber  20  and the projected texturized yarn  14  is drawn towards the inside of the chamber  20 . 
     The suction through the moving band  40  also allows friction to be improved between the moving band  40  and the texturized yarn  14 . Thus, the segment  31 ,  32  made from the texturized yarn  14  is more easily driven by the moving band  40 . However, in order to avoid a significant slowing down of the moving band  40 , the suction needs to be limited. 
     The chamber  20  has a constant annular cross-section being delimited outwardly by the moving band  40  partially defining the first surface  22 , and inwardly by the outer surface of the shaft  26  defining the second surface  24 , both the first and second surfaces  22 ,  24  extending substantially parallel to the first axis A. Thus, the fibrous product  100 , whose shape is delimited by the first and second surfaces  22 ,  24 , is a hollow tubular product with an annular cross-section, as shown in  FIG. 3 . The cylindrical outer surface  102  of the fibrous product  100  is delimited by the first surface  22 , and the cylindrical inner surface  101  of the fibrous product  100  is delimited by the second surface  24 . 
     Therefore, depending on the shape of the first and second surfaces  22 ,  24 , fibrous products with cross-sections as shown in  FIGS. 4 to 9 , may be produced. For the fibrous products of  FIGS. 6 and 7 , two shafts  26  are used, these two shafts delimiting two inner surfaces  101 . For delimiting the outer surface  102  one or more moving bands  40  may be used. For the fibrous product of  FIG. 9 , two shafts  26 A with a belt  26 B stretched between these two shafts  26  may be used. The two shafts  26 A and the belt  26 B are shown in dotted line in  FIG. 9 . 
     After being projected from the first outlet  14  and before entering into the chamber  20 , the texturized yarn  14  is wetted with an uncured binder. The binder is applied to the texturized yarn  14  by a binder injector  55  having its outlet  56  near the first outlet  14 . The binder is the glue that, once cured, holds the filaments of the texturized yarn  14  together, in a fixed position. A typical binder, suitable for producing pipe insulators is a phenolic liquid binder, which usually requires temperatures of 200° C. or greater for curing. The binder may be a liquid based binder, usually in an emulsion or solution, or a dry binder, usually in powder form. Alternatively, the dry binder may be a thermoset polymer in fibrous form that is dispersed among the texturized yarn  14 . For instance, the binder may be cured by conventional or microwave heating it to its curing temperature, by hitting it with the light waves in the long wavelength ultra violet (UV) range. Then, the binder hardens and bonds the filaments to one another. 
     The curing chamber  51  is adjacent to and located downstream from the first chamber  20 . Both the curing chamber  51  and the first chamber  20  are integrated in the curing unit  52 . Typically, in the curing chamber  51 , there may be one or more heating compartments, for curing the binder on the fibrous product, and one or more cooling compartments. A system for providing gas to the curing unit  52  and/or sucking gas out of it (see the arrows F in  FIG. 2 ) is connected to the curing unit  52 . Additionally, heating elements (outer contact heaters and heat source from inside the shaft  26 ) may be used prior to the curing chamber  51  itself. UV-curing may also be contemplated. Curing the binder gives to the fibrous product its final structure. 
     The fibrous product  100  is moved out of the curing unit  52  by the moving band  40 . Downstream from the curing unit  52 , there is provided a cutting cell allowing the continuous fibrous product  100  to be cut at a desired length. The cutting cell comprises a circular saw  60  which continuously rotates. The saw  60  is moved radially towards the fibrous product  100  and cuts it, while moving axially along the axis A with the same linear speed as the fibrous product  100 . As the cutting process is over, the saw  60  is moved back radially and axially to perform the next cut to length. 
     Another conveying belt may be provided downstream from the saw  60 , for moving the cut fibrous product  100  further in the production line. 
     Another cutting cell may be provided for cutting the fibrous product  100  in the axial direction, so as to form an axial slot in the thickness of the fibrous product  100 . Such a slot eases the insertion of the fibrous product  100  onto a tube to be isolated. 
     Further in the production line, paper or polymer sheet, shrink type wrapping may be applied. 
     With the above method and apparatus, a fibrous product  100  with special features may be produced by projecting the texturized yarn  10  from said first outlet  14  with a projection speed much higher than the rotating speed of the first outlet  14  and the axial moving speed of said segments  31 ,  32 . Such a fibrous product  100  extends along the first axis A and has a constant cross section, i.e. it has the same section in any plane perpendicular to the first axis A (see examples of cross sections in  FIGS. 4 to 9 ). The fibrous product  100  comprises the texturized yarn  10  and a binder. The texturized yarn  10  forms curls which are superimposed while being shifted with respect to one another along a shift line, this shift line being substantially a helical line that turns around the first axis A. 
     For instance, projection speed of the texturized yarn  10  from the first outlet  14  may vary between 50 and 600 m/min, the rotating speed of the first outlet  14  may vary between 40 and 600 r/min, and the axial moving speed of said segments  31 ,  32  (which corresponds to the axial moving speed of the band  40 , in this example) may vary between 1 and 50 m/min. 
     When the first outlet  14  rotates 360 degrees around the first axis A, the helical line may extend axially along the entire axial length of the fibrous product  100 . When the first outlet  14  has an oscillatory rotating movement around the first axis A, there is a succession of helical lines, each helical line extending axially along a portion of the axial length and correlating with half an oscillation. 
     It is to be understood that although glass fibers (or filaments) are used in the above embodiment, other fibrous material such as textile or mineral fibers (e.g. cellulose fibers, fibers of rock, slag or basalt) might be used. Besides, different types of glass fibers may be used depending on the service conditions of the fibrous product. For instance, for fibrous products used in a high-temperature environment, Advantex® glass fibers may be used. For a low-temperature environment, E-glass or Advantex® glass fibers may be used. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope of the invention disclosed herein. Further, the various features of the embodiments or examples disclosed herein can be used alone or in varying combinations with each other, and are not intended to be limited to the specific combination described herein.
Method for producing a fibrous product comprising: passing a texturized yarn ( 10 ) through a first passage ( 12 ) having a first outlet ( 14 ); projecting the texturized yarn ( 10 ) from the first outlet ( 14 ), inside a chamber ( 20 ), so as to fill the chamber ( 20 ) with the texturized yarn ( 10 ), thereby forming a first segment ( 31 ) of the fibrous product; moving the first segment ( 31 ) away from the first outlet ( 14 ); and forming a second segment ( 32 ) of the fibrous product in place of the first segment ( 31 ) and contiguously to the first segment ( 31 ), as many segments as necessary being contiguously formed by repeating the above steps. Apparatus for implementing the method.