Abstract:
In a camel back cross lapper, a fiber web to be layered to form a fleece is guided from an infeed zone until its discharge in a layering zone in sandwiched manner between two transport belts extending over the arms of the cross lapper. The transport belts are extended over a layering zone on an output conveyor to cover the web freshly deposited onto the output conveyor to avoid the web from being affected by harmful aerodynamic effects created by the movement of the layering arm of the cross lapper. In an embodiment, a web buffer is combined with the cross lapper such manner that the transport belts extend through web buffer.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of EP 04 008 051.7, filed on Apr. 2, 2004, the contents of which are incorporated herein.  
       FIELD OF THE INVENTION  
       [0002]     This invention is related to the field of producing non-woven fabric or fleece made from fiber material. More particularly, the invention relates to machinery known as a cross lapper.  
       BACKGROUND OF THE INVENTION  
       [0003]     When layering a fiber web (hereinafter referred to as web) onto an output conveyor, the layering arm of the cross lapper performs a pivoting movement, wherein its lower, free end moves in close distance over the output conveyor transversely to the transport direction of the latter. If the upper end of the layering arm is pivotally attached on a pivotally mounted supply arm, the supply arm also performs a pivoting movement. A cross lapper of this type, also referred to as a camel back cross lapper, is generally known and, for instance, is described in the book “Vliesstoffe”, Verlag Wiley-VCH, Weinheim, 2000 (page 160).  
         [0004]     In known camel back cross lappers, the lower end of the layering arm is coupled to a carriage which is movably guided on rails transversely to the transport direction of the output conveyor. The carriage is connected to a drive means so that by the aid of this drive means, the pivoting movement of the layering arm, and possibly of the supply arm, is carried out.  
         [0005]     The speed at which the web is discharged by the layering arm of the cross lapper may be more than 200 m/min, but speeds in the range of 300 m/min are desirable. The free end of the layering arm must therefore move correspondingly fast over the output conveyor to prevent disturbing the material and the creation of folds in the layered web. These high speeds lead to problems caused by aerodynamic effects. A web section layered by the layering arm may lift off its base and start fluttering under the influence of aerodynamic pull. One approach to alleviate this effect has been to provide a garnished pressure roller which felts the fibers of the freshly layered fiber web with the fibers of the web layers already layered arranged underneath. Since a layering arm usually discharges fiber web in both of its movement directions, two such pressure rollers may be mounted at the layering arm, increasing the weight of the layering arm accordingly. Further, the effect caused by such pressure rollers is relatively moderate.  
       OBJECTS OF THE INVENTION  
       [0006]     It is an object of the invention to provide improved fleece laying apparatus which overcomes some of the problems and shortcomings of the prior art, including those referred to above.  
         [0007]     Another object of the invention to provide a cross lapper capable of working at a relatively high layering speed.  
         [0008]     Another object of the invention is to provide a cross lapper which holds the fiber web along all essentially all of its path through the cross lapper.  
         [0009]     Another object of the invention is to provide a cross lapper which improves the quality of the fleece material produced therein.  
         [0010]     Still another object of the invention is to provide a cross lapper which eliminates aerodynamic effects on the product manufactured.  
         [0011]     How these and other objects are accomplished will become apparent from the following descriptions and the drawings.  
       SUMMARY OF THE INVENTION  
       [0012]     The apparatus of this invention is a cross lapper for manufacturing a fiber fleece from a fiber web. The apparatus comprises: (1) a supply arm having lower and upper ends and pivotably mounted at its lower end around a stationary lower pivot axis; (2) a downwardly extending layering arm having upper and lower ends and pivotably supported at its upper end on the supply-arm upper end around an upper pivot axis parallel to the lower pivot axis, the layering-arm lower end being movable in a substantially straight path; (3) an endless output conveyor extending substantially parallel to the pivot axes and having a layering zone below the path of the layering-arm lower end; (4) two reversing rollers supported on a common carriage that is disposed below the output conveyor and is movable transversely thereto; (5) two endless transport belts juxtaposed for clamping and transporting the fiber to be layered and guided along the supply and layering arms for receiving a fiber web at an infeed zone and for layering the fiber web in the layering zone on the output conveyor under pivoting movement of the supply and layering arms, the juxtaposed belts forming a discharge nip at the layering-arm lower end, the belts extending beyond the nip in opposite directions transversely across the layering zone in proximity to the output conveyor, the belts being separately guided to the reversing rollers, back to the layering-arm lower end, and from there along the layering and supply arms to the infeed zone; and (6) drive apparatus for moving the belts, pivoting the supply and layering arms, and moving the output conveyor.  
         [0013]     Preferred embodiments of the inventive cross lapper further include a pair of discharge nip rollers supported on the layering-arm lower end, and the transport belts each pass over one of the nip rollers.  
         [0014]     In another embodiment of the inventive cross lapper, the layering-arm lower end and the carriage are connected to one another and to the drive apparatus by one of a traction rope, a toothed belt or a chain for pivoting movement of the layering and supply arms.  
         [0015]     In a preferred embodiment, the inventive cross lapper also includes a pair of discharge nip rollers supported on the layering-arm lower end, and the transport belts each pass over one of the nip rollers.  
         [0016]     In another preferred embodiment, the cross lapper further includes a pivot frame pivotably coupled to the layering-arm lower end around an axis between and parallel to the nip rollers. The pivot frame is adapted to pivot such that the nip roller which is forward in the movement direction of the layering-arm lower end is lifted and the other nip roller is lowered.  
         [0017]     In a highly-preferred embodiment, the inventive cross lapper also includes web buffering apparatus disposed upstream of the supply-arm lower end, and the buffering apparatus guides the transport belts. In this embodiment, the transport belts each include feed sections and return sections. Along the feed sections, the belts, in juxtaposed fashion, transport the fiber web from a take-up site to the discharge nip, the juxtaposed belts running through a substantially U-shaped feed path portion substantially half-wrapped over a first deflecting roller. Along the return sections, the belts move from the supply arm to the take-up site guided through U-shaped return path portions oriented in directions opposite to the orientation of the U-shaped feed path portion, each belt half-wrapping one of second and third deflecting rollers, respectively. The web buffering apparatus includes a common mounting frame rotatably supporting the three deflecting rollers, thereby providing compensated length variation of the transport belts extending to and returning from the discharge nip as the layering-arm lower end traverses the layering zone on the output conveyor.  
         [0018]     In another preferred embodiment of the inventive cross lapper, the layering-arm lower end and the carriage are connected to one another and to the drive apparatus by one of a traction rope, a toothed belt or a chain for pivoting movement of the layering and supply arms.  
         [0019]     In other embodiments, the common mounting frame is movably held in a machine stand, and in some embodiments, the common mounting frame is movably held by a pendulum.  
         [0020]     In some preferred embodiments of the inventive cross lapper, the common mounting frame is pivotably supported around the axis of the first deflecting roller.  
         [0021]     In another preferred embodiment, the cross lapper also includes a tensioning roller about which the belt from one of the U-shaped return path portions is substantially half-wrapped, and the tensioning roller is biased away from the U-shape of such return path portion.  
         [0022]     In other embodiments, the cross lapper of this invention further includes first and second independent drive rollers and a common drive roller, and the transport belts are each guided over one of the independent drive rollers and their feed sections are commonly guided over the common drive roller. In these embodiments, the common drive roller is driven at a circumferential speed that is variable with respect to the circumferential speeds of the first and second independent drive rollers, thus varying the discharge speed of the cross lapper with respect to its take-up speed.  
         [0023]     In another embodiments, the cross lapper further includes first and second independent drive rollers, the transport belts each being guided over one of the independent drive rollers, and the first deflecting roller is also a driven roller driven at a circumferential speed that is variable with respect to the circumferential speeds of the first and second independent drive rollers; thus the discharge speed of the cross lapper is varied with respect to its take-up speed.  
         [0024]     In another preferred embodiment, the inventive cross lapper further includes two return drive rollers, and each of the return sections between the supply arm and the U-shaped return path portions wrap at least 90° around a respective one of the return drive rollers.  
         [0025]     In highly preferred embodiments, the supply and layering arms each have guide rollers alternatingly contacting opposite sides of the juxtaposed feed sections of the transport belts.  
         [0026]     In other highly preferred embodiments, the inventive cross lapper further includes two return drive rollers, each of the return sections between the supply arm and the U-shaped return path portions wrap at least 90° around a respective one of the return drive rollers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  schematically shows a side view of a camel back cross lapper according to the invention with a web buffering apparatus in retracted condition of the feeding and layering arms. The figure also shows web buffering apparatus.  
         [0028]      FIG. 2  shows the camel back cross lapper of  FIG. 1  with the feeding and layering arms in an extended position. 
     
    
       [0029]     The drawings show the essential features only of the invention, and this in schematic view only, since a schematic view is sufficient for understanding the invention.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0030]      FIG. 1  shows a cross lapper  1  with a supply arm  2  and a layering arm  3 . The supply arm  2  is pivotally supported on its lower end in a lower, stationary pivot axis  4 . Layering arm  3  is pivotably supported in an upper pivot axis  5  on the upper end  2 U of supply arm  2 . The lower (free) end  3 L of layering arm  3  is movably guided above an output conveyor  6  which has a transport direction which extends in parallel to pivot axes  4  and  5 . Lower end  3 L of the layering arm  3  is coupled to an pivot frame  7  which is guided in rails (not shown) which extend transversely across output conveyor  6  on both sides of a layering zone.  
         [0031]     Traction ropes, toothed belts or chains  8  are attached onto pivot frame  7  and are guided over a plurality of deflection wheels  9  supported in a frame (not shown) around output conveyor  6 . One or a pair of wheels  9 , designated by reference number  9   a , is driven by a motor (not shown). So configured, pivot frame  7  can be moved back and forth transversely to output conveyor  6 . Both supply arm  2  and layering arm  3 , arm  3  being coupled with pivot frame  7 , each carry out pivoting movements.  
         [0032]     Two endless transport belts  10  and  11 , transporting a fiber web (not shown) to be layered, are guided over supply arm  2  and layering arm  3  and around output conveyor  6  in the area of the layering zone. Transport belts  10  and  11  determine a feeding path section in which transport belts  10  and  11  are guided in parallel between a take-up site A, at which the web is supplied, and a discharge nip B at lower end  3 L of the layering arm  3 . Thus, transport belts  10  and  11  are capable of sandwiching a fiber web between them and of supporting the web. This feeding path section extends from take-up site A via a reversing roller  12 , a driven reversing roller  13 , a deflection roller  14  close to lower pivot axis  4 , over supply arm  2  and another deflection roller  15  supported at the upper pivot axis  5 , and up to discharge nip B at lower end  3 L of the layering arm  3 . (The apparatus shown in  FIGS. 1 and 2  contain numerous deflecting, reversing, and drive rollers which will be specified primarily by reference number only and not by differentiating names.) Discharge nip B comprises two deflecting rollers  16  and  17  which are supported on pivot frame  7  at which lower end  3 L of layering arm  3  is articulated.  
         [0033]     Starting at discharge nip B, the paths of transport belts  10  and  11  separate. In the example shown in  FIG. 1 , web transport belt  10  extends transversely over output conveyor  6  and two deflecting rollers  18  up to a reversing roller  19 . Roller  19  is supported in a lower carriage  20 , which is positioned below output conveyor  6 . Carriage  20  can be moved on rails (not shown) transverse to output conveyor  6 . Reversing roller  19  reverses the direction of transport belt  10 . Belt  10  then runs over deflecting rollers  21  back to lower end  3 L of the layering arm  3 . At this point, belt  10  passes over another deflecting roller  22  and moves to a deflecting roller  23  located above upper pivot axis  5 . Belt  10  then moves along supply arm  2  to a deflecting roller  24 , a drive roller  25 , two further reversing rollers  26  and  27 , and a drive roller  28  located in the area of take-up site A. In this manner, the running path of web transport belt  10  is completed.  
         [0034]     Web transport belt  11  runs from discharge nip B at lower end  3 L of layering arm  3  via deflecting rollers  18  and below output conveyor  6  to a reversing roller  29 . From reversing roller  29 , belt  11  runs back via deflecting rollers  21 A to a deflecting roller  30  mounted close to lower end  3 L of layering arm  3 , along layering arm  3  to a deflecting roller  31  located below upper pivot axis  5 , along supply arm  2  and over a deflecting roller  42  arranged close to lower pivot axis  4  to a drive roller  32 . Belt  11  then moves over a pair of reversing rollers  33  and  34  to a drive roller  35  located in the region of take-up site A. In this manner, the path of web transport belt  11  is completed.  
         [0035]      FIG. 1  shows the cross lapper with supply arm  2  and layering arm  3  in a retracted position. Pivot frame  7 , supporting deflecting rollers  16  and  17  at discharge nip B, is located in  FIG. 1  on the left side of output conveyor  6 . In this situation, lower carriage  20  supporting reversing rollers  19  and  29  is located on the right, underneath the output conveyor  6 . Comparing  FIG. 1  to  FIG. 2 , in which layering arm  2  and supply arm  3  are extended, it can be seen that by a displacement of pivot frame  7  to the right, lower carriage  20  is moved to the left by the same displacement. Corresponding to the additional length of transport belt  10  moved onto the upper side of the layering zone caused by this movement, lower carriage  20  has moved to the left, and at the same time provided a corresponding length of transport belt  11 , which is supported by the coupling of traction ropes, toothed belts or chains  8  to the lower carriage  20 .  
         [0036]     When moving lower end  3 L of layering arm  3  from the position shown in  FIG. 1  into the position shown in  FIG. 2 , deflecting roller  16  supported on pivot frame  7  is rolling on web transport belt  11  layered by roller  16  if the speed at which web transport belt  10  is driven by its drive roller  32  is as high as the movement speed of pivot frame  7 . Since the fiber web is discharged at this speed from discharge nip B, the section of web transport belt  11  resting on the freshly layered web does not have a relative speed with respect to the web (except for the movement of output conveyor  6  transverse to the layering direction of layering arm  3 ). During this movement, transport belt  10  has a speed relative to speed at take-up site A zone which consists of the sum of the running speed of pivot frame  7  and the supply speed of transport belt  10 . The same applies to transport belts  10  and  11  for movement of pivot frame  7  in the reverse direction. Practice has shown that this relative speed between the layered fleece and transport belts  10  and  11  covering the layered fleece does not lead to problems. As mentioned above, pivot frame  7  is pivoted with respect to layering arm  3  around a horizontal axis, so that the deflecting roller ( 16  or  17 ) which is in front in the moving direction, is slightly lifted.  
         [0037]     The section located between take-up site A and an infeed zone C at the lower end of supply arm  2  of the structure shown forms web buffering apparatus  36 . On the way back from discharge nip B to take-up site A, transport belt  10 , after leaving supply arm  2 , runs over drive roller  25  and from there into a substantially U-shaped return path portion the apex of which is formed by reversing roller  26 . Belt  10  continues over another reversing roller  27  and drive roller  28  to take-up site A.  
         [0038]     On its way back to take-up site A, after leaving supply arm  2 , transport belt  11  also runs over drive roller  32  into substantially U-shaped return path portion, the apex of which is formed by reversing roller  33 . From there, belt  11  continues over a tensioning roller  34  and drive roller  35  which is located at the take-up site A.  
         [0039]     Reversing rollers  26  and  33  located in the path of transport belts  10  and  11  and forming the apexes of the U-shaped return path portions, are rotatably supported in a common mounting frame  37  on which reversing roller  12  is also supported and around which the web transporting sections of transport belts  10  and  11  are guided as a pair, in juxtaposed fashion. Common mounting frame  37  is pivotally attached at the axis of reversing roller  12  at a frame-shaped link  38 , which is only schematically shown in the drawing with a dash-dotted line. Link  38  is suspended like a pendulum in a pivot bearing  41  in machine stand M (shown in dotted line format only in  FIG. 1 ) of the cross lapper.  
         [0040]     Tensioning roller  34  is mounted on the piston of a hydraulic cylinder  39  attached to machine stand M. The force exerted by hydraulic cylinder  39  onto tensioning roller  34  tensions transport belt  11 . The tension is transferred over reversing roller  33  and through common mounting frame  37 , which acts as a two-armed lever by pivoting around the axis of reversing roller  12 . The tension is further transferred over reversing roller  26  carried by common mounting frame  37  to the returning section of transport belt  10 . Thus, both web transport belts  10  and  11  are tensioned by single hydraulic cylinder  39 .  
         [0041]     On their way over the arms  2  and  3  the transport belts  10  and  11  run over several guide rollers  40  supported on the feeding and layering arms  2  and  3 , some of the guide rollers alternatingly contacting on the one and the other side of the paired transport belt section to prevent fluttering of the transport belts on the arms  2  and  3 .  
         [0042]     Various operating states will now be described. As long as drive rollers  13 ,  25 ,  28 ,  32  and  35  have identical circumferential speeds, common mounting frame  37  stays in the position shown in  FIG. 1 . If the circumferential speed of drive roller  13  becomes higher than that of the other drive rollers, drive roller  13  pulls common mounting frame  37 , through paired transport belts  10  and  11  and reversing roller  12 , to the left in  FIG. 1 , causing the length of the web transporting sections of transport belts  10  and  11  to shorten. At the same time, the length of the returning sections of transport belts  10  and  11  increases since reversing rollers  26  and  33  are also moved to the left. Positions of rollers  12 ,  26  and  33  moved to the left are shown in dotted lines in the drawing by reference numbers  12 ′,  26 ′ and  33 ′, respectively.  
         [0043]     If, however, the drive speed of drive roller  13  becomes lower than the speed of the other drive rollers, common mounting frame  37  moves to the right (in  FIG. 1 ) so that reversing rollers  12 ,  36  and  33  reach the positions shown in  FIG. 1  by reference numbers  12 ″,  26 ″ and  33 ″, respectively. Since the displacement of the reversing rollers  12 ,  26  and  33  takes place in essentially equal amounts, transport belts  10  and  11  remain tensioned.  
         [0044]     By the aid of the movement of common mounting frame  37 , the length of transport belts  10  and  11  between take-up site A and discharge nip B can be varied. Thus, it is possible to temporarily change the speed of the web discharge at discharge nip B compared to the web infeed speed at take-up site A. This change is required for cross lapper  1 , since the speed at which discharge nip B, i.e., the pivot frame  7 , moves over output conveyor  6 , cannot be constant, since in the area of the movement reversal points of layering arm  3 , its speed must be reduced by braking to zero and then accelerated in the opposite direction after the reversal of the movement. If during these braking and accelerating phases transport belts  10  and  11  continue to discharge web through discharge nip B, web thickening would result in the marginal area of the fiber web by the cross lapper, and such variations must be prevented. Thus it is necessary to vary the speed at which the web is discharged by transport belts  10  and  11 , adapting to the speed at which pivot frame  7  moves over output conveyor  6 . This variation of the discharge speed of the web from discharge nip B can be managed by suitable control of the speed of drive rollers  13 ,  25  and  32  with respect to the speed of drive rollers  28  and  35 , wherein frame  37  carries out a substantially oscillating movement around pivot bearing  41 . This oscillating movement moves reversing rollers  12 ,  26  and  33  between positions  12 ′,  26 ′ and  33 ′ on the one hand and positions  12 ″,  26 ″ and  33 ″ on the other hand, and thereby cyclically changes the buffered web volume.  
         [0045]     The structure of web buffering apparatus  36  shown can also fulfill another task. For this purpose another movement component of common mounting frame  37  will now be explained with reference to  FIGS. 1 and 2 .  FIG. 2  shows cross lapper  1  with supply arm  2  and layering arm  3  in an extended position. It can readily be seen in  FIG. 2  that the wrapping angles of transport belts  10  and  11  on deflecting rollers  15 ,  23  and  31 , which are arranged in arms  2  and  3  in the region of upper pivot axis  5 , and on deflecting rollers  14 ,  24  and  42 , which are arranged in the region of lower pivot axis  4  of supply arm  2 , vary from the wrapping angles shown in FIG.  1 . While the change of the wrapping angles of the paired web transport belt sections and also the change of the wrapping angles at deflecting rollers  23  and  31  do not have opposite influences on web transport belts  10  and  11  as far the return sections thereof are concerned, the wrapping angle of the return section of belt  10  on deflecting roller  24  in  FIG. 2  is smaller with respect to that in  FIG. 1 , whereas the wrapping angle of the returning section of belt  11  on deflecting roller  42  is greater than in  FIG. 1 . Such wrapping angles of web transport belts  10  and  11  therefore change in opposite directions. Transport belt  10  requires an increase in the running path length of its return section, while transport belt  11  requires a decrease in the running path length of its return section. Both can be achieved by the aid of tensioning roller  34 , influenced by the hydraulic cylinder  39 , which, in  FIG. 2  presses the tensioning roller  34  to the right, resulting in common mounting frame  37  being pivoted from its position shown in  FIG. 1  in counter-clockwise direction on link  38  into the position shown in  FIG. 2 . The length of the returning section of transport belt  11  is decreased, and at the same time, the length of the returning section of transport belt  10  is increased.  
         [0046]     It is obvious that the movement of common mounting frame  37  around pivot bearing  41  of link  38  and the pivoting movement of common mounting frame  37  on link  38  around the axis of roller  12  reversing paired web transport belts  10  and  11 , superimpose on one another during operation, since the compensation of the speed difference of the transport belts  10  and  11  at discharge nip B and take-up site A and the compensation of the change of the roller wrapping angles in opposite directions must take place simultaneously.  
         [0047]     As an example of a practical embodiment of the invention, the layering width is 3,500 mm. The length of arms  2  and  3  between deflecting roller  31  and the ends of the arms is 2,800 mm each. Transport belts  2  and  3  each have a length of 21,500 mm. The movement path of lower end  3 L of layering arm  3  of camel back cross lapper  1  is 4,000 mm. In the retracted condition of arms  2  and  3  ( FIG. 1 ), arms  2  and  3  include an angle of approximately 27°, whereas in the extended position ( FIG. 2 ), arms  2  and  3  include an angle of approximately 133°. The difference in the yielding of transport belts  10  and  11  which is caused by the change of the wrapping angles on deflecting rollers  24  and  42  (in turn caused by the different arm positions during extension), is compensated by an adjustment of approximately 20 mm on tensioning roller  34  by hydraulic cylinder  39 . Frame-like link  38 , at which common mounting frame  37  is suspended, has an effective length (pendulum length) of 1,400 mm, whereas the distance of reversing rollers  26  and  33  on the common mounting frame  37  from reversing roller  12  common to the transport belts is 520 mm each. For accommodating web buffering apparatus  36 , a space of approximately 2,100 mm in front of the camel back cross lapper  1  and a height of approximately 1,740 mm is required, including link arrangement  31 .  
         [0048]     A variety of alternatives are possible and are obvious to the person skilled in the art of the present invention. For instance, reversing roller  12  supported on common mounting frame  37  may serve as a drive roller, whereas roller  13  may serve as an idling reversing roller. Furthermore, reversing rollers  26  and  33  supported on common mounting frame  37  may be drive rollers, with rollers  25  and  32  serving as idling deflecting rollers. Common mounting frame  37  could be pivotally supported in a movable carriage instead of being suspended on link  38 . Furthermore, cross lapper  1  could have four or more hinged arms in order to achieve a larger layering width without increasing height, such hinged arms being arranged and movable in accordion-like fashion. In such case, the movement of the arms would be coordinated with movement of the layering arm. In an arrangement of this type, transport belts  10  and  11  would be guided in pairs over all of the arms articulated to one another so that the fiber web is permanently sandwiched between two tightly contacting transport belts across its entire feeding path.  
         [0049]     The integration of web buffering apparatus, web guidance over the supply and layering arms, and the covering of the layered web on the output conveyor by using a single pair of transport belts offers excellent advantages over the prior art not only in view of the cost of the apparatus but also in view of the quality of the product produced. The fiber web to be layered for producing a fleece is held in this integrated device in uninterrupted fashion between the web transport belts from the take-up site to the discharge nip. The fiber web is free from mechanical loads caused by free suspension, by tensioning, and by transfer from one transport belt to the other. Such freedom from mechanical loads is not available in cross lappers which working with several movable carriages. This careful and conservative treatment of the fiber web is continued after leaving the discharge nip, since the web is accompanied by one of the transport belts, namely the transport belt that covers it directly after leaving the discharge nip. The web rests on a support and is free from exposure to unfavorable aerodynamic forces as well.  
         [0050]     While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.