Abstract:
Apparatus for variably buffering a web material, the apparatus having two endless transport belts including feed sections in which the belts are juxtaposed, and return sections, the feed and return sections being of varying lengths. In the feed sections, the belts move through a U-shaped path portion, commonly guided over a deflecting roller. In the return sections, the belts are guided through U-shaped path portions extending opposite to the U-shaped path portion of the feed sections, each belt wrapping separate deflecting rollers. The three deflecting rollers are rotatably supported on a common mounting frame movably held in a machine stand for compensated length variation of the feed and return portions.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of EP 04 005 460.3, filed on Mar. 8, 2004, the contents of which are incorporated herein.  
       FIELD OF THE INVENTION  
       [0002]     This invention is related generally to the field of web handling machinery. More particularly, the invention relates to the control of the speed of web material in web handling machinery in situations in which the relative speeds of different portions of the web fluctuate with respect to each other.  
       BACKGROUND OF THE INVENTION  
       [0003]     U.S. Pat. No. 5,590,442 describes web storage apparatus for non-woven fabrics. The web storage apparatus is located between a web producer and web processing apparatus, e.g., between a carding machine, operating at constant output speed, and fabric layering apparatus, operating at rhythmically variable take-up speeds. In such fabric layering apparatus, the transport speed of the web within the machine changes during transport depending on the movements of the layering carriage within the fabric layering apparatus. The web storage apparatus is controlled in accordance with the transport speed of the layering belts of the fabric layering apparatus, such transport speed fluctuating with the rhythm of the absolute traveling speed of the layering carriage.  
         [0004]     This known web storage apparatus consists of a U-shaped section of variable length of an endless belt conveyor extending between the web producer and the fabric layering apparatus. The web storage apparatus supplies the web output from the web producer, which produces web material at a substantially constant speed, to the fabric layering apparatus, which requires web material to be supplied to it at a fluctuating speed. The length of the U-shaped section (and thereby the length of the path that web material must travel) is varied by displacing a frame which holds a pair of deflecting rollers. A carriage-mounted endless support belt aligns with the conveyor belt in its U-shaped section, and in this section, the support belt tightly contacts the conveyor belt, thereby clamping the web material between these two belts. The web storage apparatus is therefore capable of controlling the regular web supply speed of the web producer in accordance with the variable take-up speed of the web processing apparatus.  
         [0005]     In order to accomplish the changes in the path length, also known as web buffering, the movements of the frame and the carriage must be matched with one another, which requires special effort, since a sufficient tension of the conveyor belt must always be ensured to maintain the clamping effect between the conveyor belt and the support belt in order to prevent any damage of the sensitive, unsolidified web material in the web storage apparatus. Such coordinated control is both complex and costly. Further, along some portions of the web path from the infeed from the web producer to the outfeed to the web processing apparatus, the web material is not fully clamped, leaving the web material susceptible to disturbances from drafts. Thus there is a need for web buffering apparatus which can provide the web speed-matching function between various pieces of equipment in less costly, less complex manner and provide protection for the web while maintaining a high quality level in the web material.  
       OBJECTS OF THE INVENTION  
       [0006]     It is an object of the invention to provide improved web buffering apparatus which overcomes some of the problems and shortcomings of the prior art, including those referred to above.  
         [0007]     Another object of the invention is to provide web buffering apparatus which is easily controlled.  
         [0008]     Another object of the invention is to provide web buffering apparatus which interfaces more easily with certain web processing apparatus.  
         [0009]     Still another object of the invention is to provide web buffering apparatus which protects the web material along its path through the buffering apparatus.  
         [0010]     Yet another object if the invention is to provide web buffering apparatus which is structurally simple.  
         [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 takes up a web material supplied at a take-up speed and outputs this material at a discharge speed which fluctuates with respect to take-up speed but on average matches take-up speed. The inventive apparatus includes two endless transport belts which together define a take-up site for receiving the web material therebetween and which further a discharge site for outputting the web material. The transport belts are guided in juxtaposition between the take-up site and the discharge site to clamp the web material between the belts. Each transport belt includes and feed section and a return section. Each feed section is of varying length and has a substantially U-shaped feed path portion. The belts in such feed sections together are guided over a first deflecting roller substantially half-wrapped by the belts. Each return section is also varying length, and the belts in such return sections are separately guided from the discharge site to the take-up site and each runs through a substantially U-shaped return path portion extending opposite to the U-shaped feed path portion and substantially half-wrapping one of second and third deflecting rollers, respectively. The apparatus also includes a common mounting frame rotatably supporting the three deflecting rollers and movable on a machine stand, and the common mounting frame moves substantially parallel to the U-shaped path portions. For each belt, the apparatus enables the length of the feed section to vary with respect to the length of the return section.  
         [0013]     In preferred embodiments of the inventive apparatus, the common mounting frame is movably held by a pendulum.  
         [0014]     In a preferred embodiment of the apparatus, the common mounting frame is pivotably supported around the axis of the first deflecting roller. Such embodiments may also further include a tensioning roller about which the belt from one of the U-shaped return path portions is substantially half-wrapped. The tensioning roller is biased away from the U-shape of such return path portion.  
         [0015]     In other preferred embodiments, the apparatus further includes first and second independent drive rollers and a common drive roller. 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, the common drive roller being driven at a circumferential speed that is variable with respect to the circumferential speeds of the first and second independent drive rollers. In such apparatus, the discharge speed is thus varied with respect to the take-up speed.  
         [0016]     Another preferred embodiment of the inventive apparatus also includes first and second independent drive rollers. The transport belts are each 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, whereby the discharge speed of the apparatus is varied with respect to the take-up speed of the apparatus.  
         [0017]     In a highly-preferred embodiment, the apparatus is connected to a camel back cross lapper which includes an endless output conveyor and a series of at least two arms, adjacent pairs of which are pivotably connected at common ends. The series of arms includes a supply arm and a layering arm. The supply arm is pivotably mounted on the machine stand. The layering arm has a layering-arm upper end hinged to the upper end of the adjacent arm and extending therefrom downward to a layering-arm lower end above the output conveyor. The layering-arm lower end is movable transversely with respect to the output conveyor and has two discharge rollers which form a discharge site for the web material. Ths such apparatus, the transport belts are guided in pairs along the series of arms to the layering-arm lower end, guided separately over the discharge rollers, and separately returned along the arms to the take-up site. In some embodiments, the series of arms consists only of the supply arm and the layering arm.  
         [0018]     Another embodiment of the inventive apparatus 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.  
         [0019]     In other preferred embodiments, each arm of the inventive apparatus has guide rollers alternatingly contacting opposite sides of the juxtaposed feed sections of the transport belts. The apparatus also may include two return drive rollers, each of the return sections between the supply arm and the U-shaped return path portions wrapping at least 90° around a respective one of the return drive rollers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  shows apparatus according to the invention in integral combination with a camel back cross lapper with the layering arm in a retracted position  FIG. 2  shows the apparatus of  FIG. 1  with the layering arm in an extended position. 
     
    
       [0021]     The drawings only show the essential features of the invention, and this in schematic view only, since a schematic view is sufficient for the understanding the invention.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]      FIG. 1  shows a first arm  2 , also designated as a supply arm, and a second arm  3 , also designated as a layering arm, of a camel back cross lapper  1  for fleece production. Supply arm  2  is pivotally supported at its lower end  2 L in a machine stand M (shown in dotted line format on  FIG. 1 ). A hinge H at the upper end  2 U of the supply arm  2  and the upper end  3 U of layering arm  3  provides hinging movement between arms  2  and  3 . The lower end  3 L of arm layering  3  is capable of being transversely moved above an output conveyor  60  by means of a stationary drive  4  and a toothed belt  5 , with a deflecting roller  6  of output conveyor  60  being schematically shown in the drawing. (The apparatus shown in  FIGS. 1 and 2  contain numerous deflecting and drive rollers which will be specified primarily by reference number only and not by differentiating names.) Output conveyor  60  extends perpendicularly to the direction of movement of lower end  3 L of layering arm  3  and around deflecting roller  6 . A cover belt  7  is connected to lower end  3 L of layering arm  3 . Cover belt  7  is guided over several deflecting rollers  8  on both sides of output conveyor  60  and extends over output conveyor  60  to keep air turbulence away from the laid fleece, the turbulence being caused by the movement of layering arm  3  at a discharge site B at lower end  3 L of layering arm  3 . Cover belt  7  also serves to avoid formation of folds in the fleece being produced.  
         [0023]      FIGS. 1 and 2  show a variable-volume web buffering apparatus  9  to the left of camel back cross lapper  1 . Web buffering apparatus  9  comprises two transport belts  10  and  11 , each of which runs through web buffering apparatus  9  and which is also guided over arms  2  and  3  of camel back cross lapper  1  up to the discharge site B.  
         [0024]     Transport belts  10  and  11  together determine a take-up site A at which fiber web material (not shown) coming from a web generating means (also not shown) and to be layered by cross lapper  1  is supplied into a gap between transport belts  10  and  11 . Starting out from take-up site A, transport belts  10  and  11  extend as a pair over a deflecting roller  12 , a drive roller  13 , a deflecting roller  14  and over arms  2  and  3  of camel back cross lapper  1 , wherein belts  10  and  11  are guided at hinge H connecting arms  2  and  3  over a deflecting roller  15 . From there, belts  10  and  11  run to two additional deflecting rollers  16  and  17  at lower end  3 L of layering arm  3 , at which point belts  10  and  11  are separated from one another at discharge site B, to be guided back independently from one another via arms  3  and  2  of cross lapper  1  to take-up site A. Deflecting rollers  16  and  17  together determine discharge site B at which the web supplied by cross lapper  1  is deposited by layering arm  3  onto output conveyor  60  by reciprocating pivotal movements of arms  2  and  3 .  
         [0025]     As transport belt  10  returns from discharge site B to take-up site A, transport belt  10  runs over a deflecting roller  18  arranged in hinge H of arms  2  and  3 . After belt  10  leaves supply arm  2 , it runs over a deflecting roller  19  and a drive roller  20 . From this point, it runs in a substantially U-shaped path section, the apex of which is formed by a deflecting roller  21 , to a deflecting roller  22  and a drive roller  23  at take-up site A.  
         [0026]     Transport belt  11  runs over a deflecting roller  24  located at hinge H of the two arms  2  and  3 , and after leaving supply arm  2 , belt  11  runs over a deflecting roller  25 , a drive roller  26 , and a U-shaped path section in whose apex a deflecting roller  27  is located, to a deflecting tension roller  28  and a drive roller  29  located at take-up site A.  
         [0027]     The deflecting rollers  21  and  27  located in the apexes of the U-shaped path sections of returning transport belts  10  and  11 , respectively, are rotatably supported on a common mounting frame  30  in which deflecting roller  12  is also supported. The paired feed sections of the transport belts  10  and  11  thus run around deflecting roller  12 . Frame  30  is pivotally supported in the axis of deflecting roller  12  on a frame-like swinging link  31 , which is shown in the drawing only schematically with a dash-dotted line and which is suspended like a pendulum in a pivot bearing  32  in machine stand M.  
         [0028]     Deflecting tension roller  28  is attached at a piston arm  33 A of a hydraulic cylinder  33 . A tie force exerted by hydraulic cylinder  33  onto deflecting tension roller  28  provides tension to transport belt  11 . The tie force is transferred via deflecting roller  27  and frame  30 , which acts as a two-armed lever and which pivots around the axis of deflecting roller  12  that transport belts  10  and  11  have in common, and via deflecting roller  21  onto the return section of transport belt  10 . Thus, transport belts  10  and  11  can both be tensioned by a single hydraulic cylinder  33 .  
         [0029]     On the paths over arms  2  and  3 , transport belts  10  and  11  run over several guide rollers  34  supported on arms  2  and  3 , some of guide rollers  34  alternatingly contacting both sides of the transport belt sections guided in pairs to prevent flapping of transport belts  10  and  11  along arms  2  and  3 .  
         [0030]     As long as drive rollers  13 ,  20 ,  23 ,  26  and  29  have identical circumferential speeds, frame  30  rests in the state shown in  FIG. 1 . When the circumferential speed of drive roller  13  becomes larger than the circumferential speed of the other drive rollers, drive roller  13  draws frame  30  to the left in  FIG. 1 , through paired transport belts  10  and  11  and deflecting roller  12 , decreasing the lengths of the web material feed sections of transport belts  10  and  11 . Link  31  supporting frame  30  is thus swung to the left. At the same time, the lengths of the returning sections of transport belts  10  and  11  are increased, since deflecting rollers  21  and  27 , supported on frame  30  and deflecting the return sections of the transport belts in a U-shaped manner, are also moved to the left. Positions of deflecting rollers  12 ,  21  and  27  moved to the left are indicated in the drawing with  12 ′,  21 ′ and  27 ′, respectively. If, however, the drive speed of drive roller  13  becomes smaller with respect to the drive speeds of the other drive rollers, frame  30  moves to the right in  FIG. 1  so that deflecting rollers  12 ,  21  and  27  reach the positions shown in dotted lines by  12 ″,  21 ″ and  27 ″, respectively. Link  31  supporting frame  30  is thereby swung to the right. Since the adjustment of deflecting rollers  12 ,  21  and  27  takes place in essentially equal amounts, transport belts  10  and  11  remain tensioned.  
         [0031]     By the aid of the movement of frame  30  along with link  31 , the length of transport belts  10  and  11  between take-up site A and discharge site B can be varied. Thus, it is possible to temporarily change the speed of the web discharge at discharge site B with respect to the web take-up speed at take-up site A. This change is required for cross lapper  1 , since the speed at which discharge site B, i.e., lower end  3 L of layering arm  3 , moves over output conveyor  60 , 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 acceleration phases layering arm  3  continued to discharge the web material at the constant speed of transport belts  10  and  11 , web upsetting and web thickening would result in marginal portions of the fleece web laid by cross lapper  1 , and such variations must be prevented. Thus it is necessary to vary the speed at which the web material is discharged from transport belts  10  and  11 , adapting to the speed of layering arm  3  at which this arm moves across output conveyor  60 . This variation of the discharge speed of the web material from the gap between deflecting rollers  16  and  17  at discharge site B can be managed by suitable control of the speed of drive rollers  13 ,  20  and  26  with respect to the speed of drive rollers  23  and  29 , wherein frame  30  carries out a substantially swinging movement around pivot bearing  32 . This swinging movement moves deflecting rollers  12 ,  21  and  27  between positions  12 ′,  21 ′ and  27 ′ on the one hand and positions  12 ″,  21 ″ and  27 ″ on the other hand, respectively, and thereby cyclically varies the web volume buffered in the web buffering apparatus.  
         [0032]     In a synopsis of  FIGS. 1 and 2 , a further movement component of frame  30  is now explained.  FIG. 2  shows cross lapper  1  in an extended position of supply arm  2  and layering arm  3 . It can readily be seen in  FIG. 2  that the wrapping angles of transport belts  10  and  11  on deflecting rollers  15 ,  18  and  24 , which are arranged at hinge H of arms  2  and  3 , and at deflecting rollers  14 ,  19  and  25 , which are arranged in the area of a fixed bearing point F of supply arm  2 , vary from the wrapping angles shown in  FIG. 1 . While the change of the wrapping angles of the paired transport belt sections and also the change of the wrapping angles at deflecting rollers  18  and  24  located at hinge H of the arms  2  and  3  do not have opposite influences on transport belts  10  and  11  as far as the return sections thereof are concerned, the wrapping angle of the returning section of transport belt  10  at deflecting roller  19  in  FIG. 2  is smaller compared to the position shown in  FIG. 1 . However, the wrapping angle of the returning section of the other transport belt (belt  11 ) at deflecting roller  25  is larger than in the position shown in  FIG. 1 . Such wrapping angles of transport belts  10  and  11  therefore change in opposite directions. Transport belt  10  requires an increase in the running path length of its returning section, while transport belt  11  requires a decrease in the running path length of its returning section. Both can be achieved by the aid of tension roller  28 , which is influenced by hydraulic cylinder  33 , which, as shown in  FIG. 2 , draws tension roller  28  to the right, resulting in frame  30  being pivoted on swinging link  31  counter-clockwise from its position shown in  FIG. 1  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.  
         [0033]     It is obvious that the swinging movements of frame  30  around pivot bearing  32  of pivotal link  31  and the pivoting movements of frame  30  at swinging link  31  around the axis of deflecting roller  12  deflecting paired transport belts  10  and  11  combine in operation, since the compensation of the speed difference of transport belts  10  and  11  at discharge site B and take-up site A and the compensation of the change in the opposite direction of roller wrapping angles must take place simultaneously.  
         [0034]     As an example, the laying width on output conveyor  60  can be 3,500 mm. The length of arms  2  and  3  between deflecting roller  24  and the ends of the arms is approximately 2,800 mm each. Transport belts  10  and  11  each have a length of 21,500 mm. The maximum movement path of camel back cross lapper  1  is 4,000 mm. In the retracted state of arms  2  and  3 , as shown in  FIG. 1 , arms  2  and  3  include an angle of approximately 27°, whereas in the extended position shown in  FIG. 2 , arms  2  and  3  include an angle of approximately 133°. The difference in the yielding of transport belts  10  and  11  caused by the change of the wrapping angle at deflecting rollers  19  and  25  (in turn caused by the different arm positions during extension, i.e. when the angle included between arms  2  and  3  is enlarged), is compensated by an adjustment of approximately 200 mm on tension roller  28  by means of hydraulic cylinder  33 . Frame-shaped swinging link  31 , at which frame  30  is pivotally suspended, has an effective length (pendulum length) of 1,400 mm, whereas the distance of deflecting rollers  21  and  27  at frame  30  from deflecting roller  12  common to transport belts  10  and  11  is 520 mm each. For accommodating web buffering apparatus  9 , a space of approximately 2,100 mm in front of camel back cross lapper  1  and of a height of approximately 1,750 mm is required, including swinging link arrangement  31 .  
         [0035]     A variety of alternatives are possible and are obvious to a person skilled in the art of the present invention. Common deflecting roller  12  supported in frame  30  could be, for instance, a drive roller, with roller  13  serving as an idling deflecting roller. Furthermore, deflecting rollers  21  and  27  supported on frame  30  may be drive rollers, with rollers  20  and  26  serving as idling deflecting rollers. Frame  30 , instead of being suspended on swinging link  31 , could be pivotally supported in a carriage movable on rails. Furthermore, cross lapper  1  could have four pivotably-connected arms for achieving a larger laying width, such arms being arranged and movable in accordion-like fashion to avoid an increase of the height of cross lapper  1 . Transport belts  10  and  11  would then be guided in pairs over all four arms so that the web is held along its entire path by tightly contacting transport belts.  
         [0036]     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.