Abstract:
A round baler has a frame to which side walls of a baling chamber are fixed. The frame or parts of it can be moved farther apart or closer together by a linear power motor in order to control the friction between a round bale and the side walls.

Description:
FIELD OF THE INVENTION 
   The invention relates to a round baler having a frame for receiving side walls of a baling chamber and a method for altering the friction between the side walls of a round baler and the end faces of a round bale formed in a baling chamber. 
   BACKGROUND OF THE INVENTION 
   From EP A 1364574, it is known to mount side walls of a round baler movably relative to a frame, so that they can be moved farther apart or closer together. The movement is induced by vertically pivotable arms, which are raised to open the baling chamber. As the baling chamber is opened, the side walls are moved farther apart in order that the friction upon the end faces of the round bale decreases and the round bale can thus be more easily ejected. 
   SUMMARY OF THE INVENTION 
   The problem on which the invention is based is seen in obtaining this beneficial effect of the prior art with a lower technical complexity. 
   In this way, there is no need for any dedicated mounting and adjusting device for the side walls, since these are rigidly fastened to the frame and its parts. Instead, the frame as a whole or in the outlet-side region is expanded, whereby the friction on the end-face sides of the round bale is in turn reduced. Mechanical adjusting devices with anti-friction surfaces are wholly dispensed with. It may be sufficient for only one side of the frame to be moved away. A movement in the single-digit centimeter range is enough to obtain the effect. 
   The technical complexity is least when the parts supporting the side walls can be moved relative to one another by exploiting the material elasticity of the frame or of the parts. The frame of the round baler is configured in top view substantially like a horizontal “U”, so that both the crosspiece and the two legs of the “U” can be bent by a few degrees. The correct elasticity is achieved by the shaping of the crosspiece and of the legs of the “U”, in which case material surfaces which run, in particular, in the direction of bending must be configured accordingly. 
   The frame or its parts can also be divided into zones of different stiffness, so that the less stiff zones form an imaginary pivot axis about which the parts with the side walls are moved. These zones can be formed by virtue of a different heat treatment, wall thicknesses, crosspiece heights and the like. While these zones can be configured in a one-piece part, it is also possible to create such zones by transitions or connections to the parts. By means of stiffeners or other stays, for example, parts of the frame can also be rigidly connected, so that the frame or the parts in the connection region of the stiffeners are of very stiff configuration. 
   A simple embodiment of the invention consists in the use of a joint on at least one of the parts, which joint can be produced both with a pivot point and with a flexible joint plate or the like. 
   Since the frame and the parts are of relatively strong configuration, it is sensible to effect the movement of the parts by power means, for example by hydraulic, pneumatic or electric motors, which act directly or via rods or Bowden cables upon those parts of the frame which are to be adjusted. In this context, a solution in which a hydraulic motor is clamped in place between the free ends of the two legs of the “U” is undoubtedly the simplest. 
   The one or more power means can adjust the parts whenever a bale is ejected in order to ensure its exit; they can also, however, be loaded during operation in dependence on the friction determined on the side walls by means of sensors. In this way, the power requirement for the driving of the round baler can be controlled, slippage at the compression belts or rollers can be prevented, and the bale density can also possibly be influenced. 
   The frame or its parts can be brought into each of its/their end settings by means of the power means; however, they can also always assume an inner or outer end setting and be moved out of this by means of the power means. 
   In order that both a greater adjustment of the parts with the side walls is possible and that loads upon the bearings of the belt guide rollers, of drive shafts and the like do not arise, the bearings are configured or fitted such that on their inner or outer race an axial movement is possible. 
   A method for achieving the respectively desired friction is based on predefined desired values which have been drawn up, for example, for the discharging process of the round bale, for the baling process or for the mesh-binding process. Then either the actual value on which the desired values are based is determined, for example the setting of a baling chamber door, or the friction between the round bale and the side walls. Finally, a control signal for a power means is generated, which latter adjusts the frame or its parts accordingly. The friction during the baling operation can be determined from the heat development on the side walls, from the deflection of the side walls, the forces acting upon the power means, the motional resistance of the belts, the power requirement necessary to operate the round baler, and the like. The baling chamber door can be constituted both by a door of traditional construction, which is movable about a top-situated pivot axis, or by a door which is pivotable about an axis situated substantially in the middle of the baling chamber. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An illustrative embodiment of the invention, which is described in greater detail below, is shown in the accompanying drawings, wherein: 
       FIG. 1  is a schematic side view of round baler in a setting for the baling operation; 
       FIG. 2  is the round baler according to  FIG. 1  in a view from the rear; 
       FIG. 3  is the round baler according to  FIG. 1  in a setting for the bale-discharging operation; and, 
       FIG. 4  is the round baler according to  FIG. 2  in the setting for the bale-discharging operation. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A round baler  10  shown in  FIG. 1  contains a frame  12 , a chassis  14 , a drawbar  16 , side walls  18 , a baling chamber door  20 , rollers  22 , compression means  24  and a feed unit  26 . 
   The represented round baler  10  is configured such that it can form round bales of different diameter; this is not compulsory, however, since the invention can also be used in round balers of the kind which produce equal-sized round bales. Otherwise the round baler  10  functions like other round balers. 
   The frame  12  includes a front part  28 , which extends substantially vertically and fixedly connects the chassis  14  to the drawbar  16 ; for this purpose, it has a post or the like on each side of the round baler. In the present illustrative embodiment, this front part is configured with the chassis  14  and the drawbar  16  as a rigid unit and forms the actual supporting structure of the round baler  10 ; in another illustrative embodiment, the front part  28  can itself be flexibly configured and can thus be forced apart. 
   The frame  12  additionally includes fore-and-aft extending left and a right parts  30 , which in side view, in this illustrative embodiment, are each configured almost as a right-angled triangle. These parts  30  are connected with their front end region to the front part  28 , to be precise either movably, via joints, screw connections, resilient plates, or in a welded arrangement, as in the present case. The smallest side member  32  of the triangle, which is only indicatively present, substantially overlaps with the front part  28 , or alternatively is formed by the latter, or, in another embodiment, bears against its inner face. A corner region  34  of the triangle is located at a upper corner region of the round baler  10 , so that an upper side member  36 , the hypotenuse or, in any event, the longest side member, runs almost horizontally. The middle or medium-sized side member  38  extends rearwards and upwards from a mid-height location on the front part  28  to the corner region  34 , via the middle region of a baling chamber  40 . The parts  30  are connected to each other, almost on half of their fore-and-aft extending length by an upper stiffener  42 , which is welded or screwed to the upper side members  36 . In addition, on each side, a lower stiffener  44  is provided, which respectively connects the right and left parts  30  rigidly to the front part  28 . The connection of the parts  30  by means of the stiffener  42  and their rigid connection to the front part  28  by means of the stiffeners  44  results in the frame  12  not being able to be bent apart in the region of the stiffeners  42 ,  44 ; an imaginary pivot axis  46  running through the two stiffeners  42 ,  44  is therefore obtained with a major resilient zone of the left and right parts  30  and the attached left and right side walls  18  being thus defined rearward of the imaginary pivot axis  46 . The position of the stiffeners  42 ,  44  can be chosen such that the pivot axis  46  is at a desired location, whereby the motional behavior of the parts  30  can be influenced. In particular, the position of the stiffeners  42 ,  44  can be altered according to the round baler model. 
   Between the corner regions  34  of the two parts  30  there is disposed a power means  48 , which in the present illustrative embodiment is configured as a linear hydraulic motor, a so-called hydraulic cylinder, and can be retracted and extended, a small stroke of just a few centimeters being sufficient. Since the power means  48  actively operates only in one direction, in the case of a hydraulic or pneumatic motor it can take the form of a single-acting type. In the present illustrative embodiment, the alignment of the parts  30  is chosen such that in a normal position they and the attatched side walls  18  run parallel to one another, i.e. the power means  48  is extendible when pressurized to force the parts  30  apart to a deflected position, wherein they and the attached side walls diverge rearwardly from each other and is thereafter retracted by virtue of the elasticity of the parts  30  when the pressure is exhausted so that there is zero pressure. Because of the arrangement of the power means  48  in the corner regions  34 , a large lever arm is obtained and, thus, does not need to apply high forces; clearly, the power means  48  could also act upon another location, in which case, however, regard would have to be paid to possible torsional forces or flexions in other directions. 
   The side walls  18  are configured as single-part or multipart panels with external reinforcements, which extend substantially over the cross section of the baling chamber  40 . The side walls  18  are screwed or welded onto the inner sides of the parts  30  and delimit the baling chamber  40  at the end faces of a round bale (not shown). Owing to the connection of the side walls  18  to the parts  30 , the side walls  18  also move when the parts  30  are forced apart, and thus away from the end faces of the round bale, whereby the friction on the side walls  18  is reduced or even eliminated. 
   The baling chamber door  20  contains two triangular swivel frames  50 , which can be pivoted by means of actuating means (not shown, but known per se) about a bearing  52  in the middle region of the baling chamber  40  vertically out of a lower setting shown in  FIG. 1  into an upper setting shown in  FIG. 3 . In the lower region of the swivel frames  50 , rollers  22  are provided, which run transversely to the longitudinal centre plane of the round baler  10  and over which the compression means  24  can run and support the round bale—they, too, are part of the baling chamber door  20 . In the lower setting of the swivel frames  50 , these, with the rollers  22  and the compression means  24 , close off the baling chamber  20  in the downward direction. When the baling chamber door  20  is swung upwards, the rollers  22  and those strands of the compression means  24  which run over them free up the baling chamber  40  in the downward direction. The swivel frames  50  run on the outer side of the side walls  18 , where the bearings  52 , too, are located; the rollers  22  supported on the swivel frames  50  extend, however, beyond the contour of the side walls  18 . Since the bearings  52  are located on the side walls  18  or, alternatively, on the lower, middle side members  38  of the parts  30 , they, too, jointly move when the parts  30  are forced apart; in this case, either the bearings  52  in the swivel frames  50  can move axially or the latter are likewise bent slightly outwards. 
   The rollers  22  are provided both on the swivel frames  50  and on the side walls  18 , but also on a tensioning device  54 , which is located in the front upper region of the round baler  10  and has tensioning arms, springs and the like, as this is known per se. Further rollers  22  are provided in a likewise known manner in the region of the feed unit  26 . In total, the rollers  22  serve to support, drive and divert the band-like compression means  24 . The rollers  22  situated in the region of the parts  30  are mounted such that a movement of the parts  30  in the direction of longitudinal extent of the rollers  22  is possible, which can be achieved, for example, with plain bearings and the like. 
   The compression means  24  are configured as continuous belts or bar chains and run according to the drawing and in a manner which is known per se over the rollers  22 . The baling chamber  40  could also be surrounded by fixedly or movably fitted rollers  22 , as is likewise known in the prior art. The compression means  24  form a loop, which extends from the feed unit  26  and in which the baling chamber  40  is formed and the received material to be compressed is rolled up into a round bale, which is delimited at its end faces by the side walls  18 . 
   The feed unit  26  includes in this case a so-called pick-up and a feed rotor without a cutting device; these stand purely illustratively for a multiplicity of other feed units  26 , which are known in their entirety and need no further description. 
   On the round baler  10  there are provided in this case three sensors, whereof a sensor  56  detects the setting of the baling chamber door  20 , a sensor  58  detects the tension prevailing in the frame  12  in the direction of the rotational axis of the round bale and a sensor  60  detects the power requirement for the drive. By means of at least one of these sensors  56 ,  58 ,  60  and a control device, it is possible to determine the potential magnitude of the friction on the side walls  18  and to set a desired value. Likewise, the discharging process for discharging the round bale from the baling chamber  40  can be detected and tracked, whereupon a signal is transmitted to the power means  48  to widen the baling chamber  40  so as to reduce the friction. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.