Patent Publication Number: US-2006000193-A1

Title: Guiding and retaining mechanism for a bale wrapper

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS  
      Priority, and incorporation by reference, is hereby claimed under 35 U.S.C. 119 to Great Britain Patent Application GB 04133336.9, titled “Guiding And Retaining Means For A Bale Wrapper”, filed Jun. 15, 2004, and having Karel O. R. Naeyaert and Danny N. O. Claeys as inventors.  
     FIELD OF INVENTION  
      The present invention relates to machines for wrapping sheet material around bales of agricultural products, such as silage. More particularly it relates to mechanism for guiding and holding a slip of wrapping material at the end of and between wrapping cycles.  
     BACKGROUND OF INVENTION  
      Machines for wrapping sheet material, such as coated plastic film, around bales of agricultural products are well known in the art. They are used for applying an airtight wrapping around the bale in order to prevent later ingress of air and to induce a fermentation process that improves the storing qualities of the product, which may be silage grass, haylage, alfalfa or other. Most wrapping machines are designed for wrapping cylindrical bales, which are produced by the so-called round balers, but there also exist wrappers for rectangular bales, which may be made by large, high-density balers. A common type of wrapper comprises a stationary table, which rotates the bale about a horizontal axis. While the bale is rotated, one or a pair of film dispensers applies the film around the bale surface. The dispenser is mounted to a satellite arm, which is rotated about a central, upright axis in order to revolve the dispenser around the bale. At the end of the wrapping cycle, a guiding and holding arm catches the film between the dispenser and the bale and the satellite arm is stopped. The arm guides the film to a knife, which cuts the film loose from the bale. The free end of the film is pulled against the bale, but it is of no concern if a short end would hang loose. The guiding and holding arm holds the other end of the film against a retainer. The wrapped bale is discharged from the wrapping machine, which is now ready for receiving a new bale. At the start of the next wrapping cycle, the dispenser is rotated around the bale for at least one turn, while the end of the film is still being held against the retainer. When the film is secured against the bale by at least one overlapping layer of film, the guiding and holding arm will release the start end of the film, which is then caught between the bale and the newly dispensed film and finally disappears below the subsequently applied film layers.  
      The wrapping machine in the baler-wrapper combination New Holland 548 Combi™ is provided with two guiding and holding arm assemblies, which are pivotable between an upper, film catching position, and a lower, film cutting and holding position. In the upper position, the arm extends between the bale and the trajectory of the dispenser. After a strip of film has been pulled over the upright arm, the latter is moved downwards to the knife and a holding pad. The arm should not tear the film apart prematurely, because a loose end of wrapping material would prevent a proper start of a new wrapping cycle as described above. Therefore, the arm comprises along its full length a roller, which is mounted for contacting and guiding the film strip. During downward movement of the arm, the roller is rotating along the coated film surface, which thereby gets no opportunity to stick permanently to the roll.  
      However, it has been experienced that for certain film qualities, especially for aged film, there is a tendency for the strip to migrate along the roll to its outer end. When the arm is in an inclined position to the sheet film, the rotation of the roller along the surface will impose an outward force upon the film and screw it outwardly. It is possible that the upper border of the film strip finally reaches the end of the arm and hooks behind the extremity of the roll. The film starts tearing and it is possible that it is damaged to the extent that it is pulled loose from the guiding and holding arm. Then there will be no convenient starting end for the next bale and the operator will have to intervene in order to provide a new starting end between the arm and the dispenser and to restart the wrapper. Such operation is particularly time-consuming as the operator has to interrupt the baling operations, stop the tractor and leave the tractor cab to refit the loose end of wrapping material.  
      Accordingly, there is a need for guiding and holding mechanism, which on the one hand smoothly guides the film material towards its hold position, and on the other hand precludes an outward migration of the film over a distance longer than the length of the guiding and holding mechanism itself.  
     SUMMARY OF INVENTION  
      According to the invention, there is provided a machine for wrapping sheet material around a bale of agricultural product, said machine comprising: a table for receiving said bale and rotating the same about a first axis; a dispenser unit for holding a roll of said sheet material and dispensing said sheet material to said bale; mechanism for rotating said dispenser unit relative to said bale about a second axis, substantially perpendicular to said first axis; and an arm assembly movable between a first position in which said arm assembly extends between said bale and the trajectory of said dispenser unit, and a second position in which said arm assembly is capable of holding an end of said sheet material, said arm assembly comprising a roller extending lengthwise of said arm assembly and capable of rotating around its axis, characterised in that said arm assembly further comprises a stationary guide member, extending outwardly from said roller and positioned to receive a border of said sheet material during the movement of said arm assembly.  
      The stationary guide member prevents that sheet material, such as film, which is screwed outwardly along the roller during the downward movement of the arm assembly, reaches the end of the same and hooks there behind, such that the film is not torn before the next wrapping cycle is started.  
      Advantageously, the stationary member may comprise a cylindrical member having substantially the same outer diameter as the rotatable roller. This structure provides a smooth transition for the film and reduces the chances of the film tearing when it reaches the stationary portion. A member having a diameter that is slightly smaller than the roller, would equally be effective.  
      The member may be immobilised by a clamp that is installed between the member itself and a mechanism on the arm assembly for cutting the sheet material at the end of a wrapping cycle. Such mechanism may comprise an element that holds the sheet material against a knife blade. The position of this element may be adjustable in order to optimise the cutting action. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      An embodiment of the present invention will no be described in further detail, by way of example only, with reference to the accompanying drawings, in which:  
       FIG. 1  is a generally diagrammatic side view of baler-wrapper combination, comprising a wrapping machine according to the invention;  
       FIG. 2  is a somewhat simplified, perspective view of the wrapping machine of  FIG. 1 , comprising a pair of guiding and holding mechanism;  
       FIG. 3  is a perspective view of one of the guiding and holding mechanism of  FIG. 2  in a closed position;  
       FIG. 4  is an exploded view of the guiding and holding mechanism of  FIG. 3 ; and  
       FIG. 5  is a perspective view of the guiding and holding mechanism of  FIG. 3  in an open position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIEMENT  
      The machine shown in  FIG. 1  is a baler-wrapper combination  1 , comprising a baler unit  2  and a wrapping unit  3 , both mounted to a wheeled frame  4 . The baler unit  4  shown is a round baler, provided with a pick-up assembly  5  for picking up crop material from a field and feeding it to a cylindrical baling chamber  6 . The crop material is collected and compressed inside the baling chamber  6  to form a cylindrical bale, which is stabilised by applying twine or net around its cylindrical periphery. Upon completion of the bale, the tailgate  7  of the baler unit  2  opens to enable transfer of the bale to the wrapper unit  3 .  
      As shown in  FIG. 2 , the wrapper unit  3  is provided with a transfer mechanism  9  for receiving the finished bale and transferring it to a wrapping table  10 . The transfer mechanism illustrated comprises a fork  12 , which is pivotable about a transverse axis  13  adjacent the front end of the wrapping table. It is also conceivable to use other transfer mechanism such a horizontal belt or chain conveyor, or a shuttle table, which is placed below the open tailgate for receiving the bale and which is moved backwards along a pair of rails or other convenient guide mechanism to transport the bale to the wrapping table  10 .  
      The wrapping table  10  comprises a conveyor  15 , e.g. a belt or chain conveyor, which extends between transverse front and rear axes  16 , 17 . The bale is received and held on the top run of the conveyor  15 . Operation of the conveyor makes the cylindrical bale rotate about its own, horizontal axis. It is also possible to replace the conveyor assembly with a pair of transverse rollers, of which one or both are driven to rotate the bale.  
      The wrapper unit  3  comprises an upper frame  19 , affixed to the frame  4  and extending above the area for the bale. The upper frame supports a satellite motor  20  from which extend a pair of satellite arms  21 . These arms each support a film dispenser unit  22 , which comprises a mechanism for rotatably holding a roll  23  of wrapping film, and a prestretcher mechanism for prestretching the film before it is applied to the surface of the bale. Such dispenser units are well known in the art and will not be described in further detail. Commonly, the wrapper units are provided with two dispenser units, but it is also possible to use a wrapper having only one dispenser unit.  
      During wrapping operations the satellite motor  20  is energised to rotate the dispenser units  22  around the bale, while conveyor  15  of the wrapping table  10  rotates the bale around its horizontal axis. The film from the roll  23  is prestretched and wrapped around the surface of the bale.  
      A guide and holding mechanism  25  is provided on each side of the wrapper unit  3 . As shown in FIGS.  3  to  5 , it comprises a movable arm assembly  26  and a stationary cradle assembly  27 . The latter assembly  27  comprises a support bar  29  which is bolted to a horizontal beam of the frame  4  and a knife table  30 , which is mounted by a transverse pivot bolt  31  to the support bar  29 . This mounting allows some limited pivotment of the knife table  30 , when the arm assembly  26  comes to rest there against as described hereinafter. The knife table  30  comprises a generally U-shaped profile, which holds at its bottom a rubber pad  33 , and a knife blade  34 , extending along substantially the full length of the knife table  30 . The knife blade is securely held against an inner wall of the profile by a knife retainer  35 . The outer tip of the knife is serrated in order to induce a positive tearing of the wrapping film in this area.  
      The arm assembly  26  comprises a cylindrical rod  37 , to which are welded two downwardly extending lugs  38 . The lugs are mounted on both sides of a bearing  40 , which is affixed to the support bar  29 , and pivotably connected thereto by a pivot pin  39 . A knife clamp  42  extends parallel to the rod  37  over its full length. It is mounted to the ends of the rod  37  by a pair of bolts, which allow angular adjustment of the clamp  42  about the rod axis. Most of the rod  37  is received in a roller  43 , which rotates freely about the rod itself. The roller is made out of plastic material, but it also conceivable to use metal, as long as low-friction rotation between the roller and the sustaining rod is made possible. The outer section of the rod  37  carries a further cylindrical member  44 . This member  44  has the same diameter and is made out of the same material as the roller  43 . However, it is not permitted to rotate freely about the rod axis. To this end it is held in place by an angled clamp  45 , which is inserted between the knife clamp  42  and the cylindrical member  44 .  
      The arm assembly  26  can be moved between a substantially horizontal position, as shown in  FIG. 3 , and an upright or angled position, as shown in  FIG. 5 , by a hydraulic cylinder  49 . The rod end of the cylinder  49  is connected by a pin  50  to the outer ends of the lugs  38  of the arm assembly  49 , and the chamber end is connected by a pin  51  to lugs  52 , which extend downwardly from the support bar  29 .  
      During wrapping operation the dispenser units  22  are rotated around the bale, which is rotated about its own axis by the conveyor  15  of the wrapping table  10 . The material from the film rolls  23  is pulled through the pre-stretcher units, which extend the film and release more adhesive material to the film surface. The pre-stretched film is applied onto the surface of the bale. During this phase the guide and holding mechanism  25  are in their lower position, as shown in  FIG. 3 , such that there is no interference between the arm assembly  26  and the run of film between the dispenser units  22  and on the bale.  
      When the bale is completely wrapped, the arm assembly  26  is raised to the position of  FIG. 5 . At the next passage of the dispenser unit  22 , the arm assembly  26  is caught by a stretch of film material. The satellite motor  20  is halted and the arm assembly  26  is lowered, thereby pulling the film material downwardly towards the cradle assembly  27 . The movable roller  43  engages the coated side of the film and rotates therealong while stretching the film somewhat further. The rotation of the roller  43  divides the forces on the film over the film sections on both sides of the arm assembly  26 , such that it does not reach its stretch limit and does not start to tear apart. While the arm assembly  26  pivots downwards, the upper edge of the film is screwed along the rotating roller  43  towards the outer end of the rod  43 . Eventually, this edge reaches the stationary member  44 . It still can slide along this member  44  of the arm assembly  26 , but the screwing action on this part of the film has stopped. Accordingly, there is no tendency anymore for the upper strip of the film to migrate to the outer end of the rod  37  and to get hooked behind the same. Further film material driven outwardly by the rotating roller  43 , will be pushed against the halted film border and start to wrinkle in the same area without breaking.  
      As the film edge is stopped adjacent the stationary member  44 , it is not stretched as far as it would have been in case the roller  43  extended over the full length of the arm assembly  26 . Chances of tearing are thereby also reduced.  
      The arm assembly  26  finally arrives at its horizontal position, wherein it catches the film between the roller  43  and the rubber pad  33  of the cradle assembly  27 . The knife clamp  42  pushes the film against the knife blade  34 , which tears the film and cuts the stretch between the cradle assembly  27  and the bale loose from the stretch between the cradle assembly  27  and the dispenser unit  27 . The latter portion is kept in place by the arm assembly  26 , while the first portion is released and floats against side surface the bale. Then the wrapping table  10  is pivoted rearwardly to deposit the wrapped bale onto the field.  
      The wrapping table  10  re-assumes its original, horizontal position and the dispenser units  22  and the guide and holding mechanism  25  are held stationary, until the transfer mechanism  9  load a fresh bale of crop material on the wrapping table  10 . Then, the wrapping table  10  and the satellite arms  21  start to rotate at a slow speed. The dispenser units  22  dispense the film around the bale, while the outer slip of the film is still being held against the rubber pad  33 . The presence of a wrinkled film section near the upper border improves it resistance against tearing during this phase. When the dispenser units  22  have completed at least one revolution, the cylinders  49  raise the arm assemblies  27  for a short period in order to release the film end. Thereafter the arm assemblies  27  are lowered again to prevent interference with the newly applied film or with the rotating dispenser units  22 . The satellite motor  20  is then driven at full speed for wrapping the remainder of the bale surface. The slip of film material which has been released from the guide and holding mechanism  25 , floats against the bale surface and is covered by the subsequent layers of film.  
      Hence, there is provided a guiding and holding mechanism  25  that is capable of guiding the film material smoothly to a holding position and which is not prone to defective operation caused by the tearing of said film during said guiding operation. The rotatable guide roller  43  allows relative movement between the film and the guiding mechanism, thereby precluding excess local tensions that would break the film, and the outer stationary member portion limits the movement of the film to a location where it hooks behind the guiding mechanism itself.  
      Although the present invention has been described with reference to a particular wrapping machine, it should be understood that the invention is not limited to this particular embodiment. Other embodiments can be thought of without departing from the scope of the invention as defined by the claims. For instance, the invention may equally be applied in an independent wrapping machine, which is not linked to a baler. It may also be used in a wrapping machine of the type using one or two stationary dispensers and a wrapping table that rotates about a central, upright axis. The stationary member at the outer end of the rod may equally be secured by conventional connection mechanism such as bolts or glue.