Abstract:
Upon detecting a blockage in the intake duct of a square baler, the path of the tines is temporarily modified from the normal path to a path whereby only a fraction of the crop material accumulated in the intake duct is loaded into the baling chamber. Subsequently the path of the tines is restored to the normal path.

Description:
This application is the US National Stage filing of International Application Serial No. PCT/EP2010/060228 filed on Jul. 15, 2010 which claims priority to Belgium Application BE2009/0456 filed Jul. 28, 2009, each of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to agricultural balers for the formation of square bales of crop material, such as hay, straw or silage in a bale chamber. 
     BACKGROUND OF THE INVENTION 
     In a conventional baler, as shown for example in U.S. Pat. No. 4,106,267, hay, straw, silage or similar crop material that has been previously cut, windrowed or swathed, is picked up from the ground by a pick-up unit, fed into a duct by a packer unit and loaded in successive batches or charges into an elongated bale chamber by tines of a stuffer unit in timed sequence with a reciprocating plunger. The plunger compresses the material into bales and, at the same time, gradually advances the bales towards the outlet of the bale chamber. As the bales reach a predetermined length as determined by a metering device, a knotter device is actuated which wraps cord, twine or other flexible binding material around the bale and secures the ends of the binding material together. Instead of a packer unit it is also known to use for example a rotor cutter unit which chops the crop material into smaller pieces. 
     The packer or rotor unit pre-compresses the crop material in the precompression chamber against a backstop formed by the plunger, when closing off the entrance of the bale chamber. The stuffer unit is designed to transfer charges of the crop material quickly into the bale chamber within the short interval during which the reciprocating plunger clears the entrance of the bale chamber. Typically this is accomplished by a fork assembly of which the arms are rotatably connected to cranks, the arms being provided with longitudinally extending slots in which stationary journals are received. A uniform revolution of the cranks makes the arms shift along and pivot about the journals so that the tines of the fork travel along a generally kidney-shaped path with a varying speed. The maximum or peak speed is obtained when the distance between the connection to the cranks and the stationary journals reaches its minimum, since the arms then act as levers with very close fulcrum points. Such a system permits a quick sweep of the material behind the packer unit through the duct and to the entrance of the bale chamber. 
     This type of stuffer unit was originally designed for the baling of dry, low density material such as straw or hay, but meanwhile there has been an important shift in agriculture from the use of hay to the use of silage. Silage grass can also be baled, but since it has a higher humidity, a higher density and generates higher friction forces with the walls of the precompression chamber than the other crop materials, the load on the components of the stuffer unit increases accordingly. 
     A stuffer overload protection, will be triggered if for example a plug of crop material is formed in the precompression chamber, especially during the baling of silage. A conventional protection is the use of a shear bolt assembly in the drive line of the stuffer unit. When the loads exceed the shear strength of the bolt, the stuffer is disconnected before its components are damaged. The shearbolt can be replaced relatively easy, but in certain cases it will not be possible to restart the normal operation of the baler as the stuffer unit will not be able to remove the crop material in the precompression chamber without activating the overload protection. In this case it will cost the operator valuable time to render the baler operable again, because it will be required to clear the precompression chamber manually before the baler can be restarted. Furthermore this is a job that requires extensive safety precautions and it is very difficult to gain access to the intake duct of the precompression chamber. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore desirable upon detection of an overload condition to be able to clear the blockage of the precompression chamber without the need to clear the intake duct manually. 
     According to a first aspect of the present invention, there is a provided a method for clearing a blockage in the intake duct of a square baler which comprises:
         a baling chamber with an inlet for the introduction of crop material   an intake duct for transporting crop material to the inlet; and   a stuffer comprising tines movable to follow a generally kidney shaped path to load the crop in the intake duct into the baling chamber through the inlet, characterised in that the method comprises the steps of:   detecting a blockage in the intake duct;   temporarily modifying the path of movement of the tines from the normal path to a path whereby only a fraction of the crop material accumulated in the intake duct is loaded into the baling chamber; and   restoring the path of the tines to the normal path.       

     After the path of movement of the tines has been restored to its normal setting, it is possible to perform a further cycle of the stuffer mechanism without picking up more crop material to transfer the remainder of the slice that caused the blockage into the baling chamber. It is also possible simply to resume normal operation so that the crop remaining in the intake duct forms part of the next slice to be loaded into the baling chamber. 
     According to a second aspect of the present invention, there is provided a square baler for performing the method according to the first aspect of the invention, characterised in that the tines of the stuffer are movable by means of a mechanical linkage of which the geometry is variable to modify the path of the tines. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a fragmentary diagrammatic side elevation of a baler comprising an intake duct and a stuffer arranged beneath a bale case; 
         FIG. 2  is an enlarged side view of the stuffer; and 
         FIGS. 3 to 5  show details of three alternative embodiments of pivot plates of the stuffer shown in  FIGS. 1 and 2  in order to implement the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment of the invention is implemented as a modification of the stuffer mechanism described in EP 0 636 308. The accompanying  FIG. 1  and in part  FIG. 2  correspond to the same figures of EP 0 636 308, and the remainder of the same specification is hereby imported herein by reference to avoid unnecessary repetition. 
       FIG. 1  shows a baler  1  having a fore-and-aft extending bale case  10  with a rectangular cross section defining a baling chamber. The bale case  10  is supported in an upwardly and forwardly inclined manner by struts  14  having ground-engaging wheels  16  at their lowermost ends. A downwardly and forwardly projecting drawbar  18  at the front of the bale case  10  is adapted for hitching the baler  1  to a towing vehicle (not shown) for advancing the same across a field. An enclosed plunger  20  reciprocates fore-and-aft within the baling chamber for periodically compacting material presented to the chamber through an inlet  22  in the floor  24  of bale case  10  across the full width thereof. 
     An upwardly curved loading or intake duct  26  depends from the bale case  10  and has its upper discharge end  28  in registration with the inlet  22 , while the lower receiving end  30  of the duct  26  is remote from inlet  22  and is disposed substantially forwardly thereof. The duct  26  has a curved top wall  32  which is provided with laterally spaced, longitudinal slots (not shown) extending over its full length, and a solid curved bottom wall  36 . The lower end  30  of the duct is positioned directly behind a crop pick-up  40  which may be of any design capable of picking up windrowed or swathed crop material from the field and delivering the crop material rearwardly into the end  30  of the duct  26 . In the illustrated embodiment, the pick-up  40  has a series of lifting tines  42  that sweep the crop upwardly to stub augers  44  which gather the crop centrally and deliver it rearwardly into the lower end  30  of the duct  26 . 
     A packer unit  48  is positioned directly behind the crop pick-up  40  and above the duct end  30  for making a pre-compressed charge of material within the duct  26  preparatory to loading the bale case  10 . The packer unit  48  comprises a plurality of forks with tines  50  which are moved along a generally kidney-shaped path (not shown) to thereby project into the crop material in the lower end  30 , push charges of the crop material rearwardly and upwardly in the duct  26  and retract from the duct  26  while returning to their foremost position. 
     Alternatively instead of the packer unit  48  there can be provided a known rotor cutter system which chops the crop and projects it into the intake duct  30 . 
     A power input shaft  52  along the drawbar  18  carries a flywheel  54  at the upper end of the drawbar  18 , immediately adjacent a right angle gearbox  56  coupled with the input shaft  52 . The gearbox  56  drives a pair of crank arms  58  which are rotatably linked to a pair of pitman arms  60  of the plunger  20 . When rotating power from the towing vehicle is supplied to the input shaft  52 , the gearbox  56  rotates the crank arms  58  to cause the plunger  20  to reciprocate within the bale case  10 . The same gearbox  56  drives a shaft  86  of a sprocket  84 . Other output shafts (not shown) of the gearbox  56  provide either directly or indirectly driving power to the packer unit  48 , the pick-up  40  and the stub augers  44 . 
     Behind the packer unit  48  and above the intake duct  26  there is mounted a stuffer comprising a stuffing fork  66  for periodically sweeping an accumulated charge of crop material from the duct  26  into the bale case  10 . The fork  66  has a transverse square tube  68  spanning the duct  26  above the latter, to which tube  68  a series of laterally spaced-apart, elongated tines  70  is attached. It is clear that the tube  68  can alternatively be formed as for example a round tube or as having an other suitable section. The tines  70  are spaced apart in accordance with the slots in the top wall  32  of duct  26 , such that during the loading cycle the tines  70  may enter the duct  26  through said slots and move along the bottom wall  36  toward the inlet  22  of the bale case  10 . 
     The fork  66  also includes a pair of levers  72  at opposite ends of the tube  68 , which levers  72  carry the square tube  68  at their rearmost end and are rotatably coupled at their foremost end with a pair of cranks  74  through pivots  76 . The cranks  74  are rigidly affixed to opposite ends of a shaft  78  that spans the bale case  10  above the packer unit  48 . The crank  74  on the left side of the baler  1  is also rigidly connected by a shear bolt (not shown) to a large sprocket  80 , which receives driving power from an endless chain  82  entrained around the drive sprocket  84 , carried by the drive shaft  86 . It is clear that other known arrangements are possible to deliver driving power to the stuffing fork  66 . It is for example possible to use gearboxes. In this manner the foremost or operated end of each lever  72  is mounted for movement in a circular path of travel about the axis of shaft  78 . 
     According to a known alternative embodiment the shearbolt for the stuffer is located in the lever  72  where it connects this lever  72  with the tines  70 . When the shearbolt breaks the tines  70  are pivoted away from the intake duct  30  by means of springs around a pivot point in the region of tube  68 . 
     As more clearly shown illustrated in  FIG. 2 , the rearward ends of the levers  72  are guided by a pair of journals  88 , which serve as lever fulcrums, engaged in longitudinally extending slots  90  in the levers  72 . The journals  88  fit closely within the sides of the slots  90  so as to make the journals  88  follow a predetermined path  91  (shown in dashed lines in  FIG. 2 ) relative to the levers  72 . The journals  88  are rotatably mounted to two generally triangular pivot plates  94 , which are pivotably attached to the left and right side of the bale case  10  through a pair of pivots  96 , positioned behind and slightly above the crank drive shaft  78 . 
     According to a known alternative embodiment there can be used a full cam wheel and rubber damping blocks to position the pivot levers. 
     The journals  88  and pivot plates  94  are forced upwardly by springs  99 , of which the one end is attached to the upper half of the plates  94  and the other end to the bale case  10 . The plates  94  are held in a first position as shown in full lines in  FIG. 2  by a pair of stop bolt assemblies  98 , comprising supports, which are affixed to the bale case  10 , and stop bolts, interacting with abutments  100  attached to and extending from the lower edge of the pivot plates  94 . The bolts and nuts of the assemblies  98  are adjustable to modify this first, uppermost position of the journals  88 . 
     The front portion of the longitudinally extending slots  90  is filled with plugs  106  that are secured to the levers  72  by a rim fitting over the front portion of the slots  90  and by bolt means (not shown). 
     Opposite to the lever pivots  76  the cranks  74  comprise arms, incorporating cam members  102 , which have substantially straight and substantially circular portions, the latter being coaxial with the drive shaft  78 . When the cranks  74  are rotated clock-wise as viewed by a person looking at the left of the baler, first the straight portions of the cam members  102  come into contact with rollers  104 , which are rotatably connected to the pivot plates  94 , and push said plates  94  upwardly, and subsequently the circular portions keep the rollers  104  and the pivot plates  94  in a stationary position. The bolt assemblies  98  are adjusted to almost engage the abutments  100  during the run of the rollers  104  over the circular portion of the cam members  102 . 
     As more fully explained in EP 0 636 308, the combined action of rotating the pivots  76  in a circular path and moving the journals  88  through an arc centred on the stationary pivots  96  in phase with the rotation of the cranks  74  is to cause the tips of the tines  70  to travel along a kidney shaped path shown in dotted lines in  FIG. 2  and designated  92 . 
     The tines  70  are shown in  FIG. 2  at the point of completion of a stuffer cycle. At this point, a slice of the crop that has been pre-compressed in the intake duct  26  has just been pushed by the tines  70  through the inlet  22  in the bale case and intake duct  26  is being refilled. 
     Once the desired quantity of crop has been built up in the intake duct  26 , the next stuffer cycle is commenced. The tines  70  are retracted from the intake duct  26  and move along the part of the kidney shaped path  92  lying outside intake duct  26  until they arrive at the lower end of the intake duct  26 . The tines  70  are then driven back into the intake duct to engage the lower end of the crop slice that has collected within the intake duct  26 . The tines  70  then follow the section of the kidney shaped path  92  lying within the intake duct  26  sweeping the slice up through the open inlet  22  into the baling chamber forward of the plunger  20 . 
     The size of the slice transferred into the baling chamber in each cycle of the stuffer is dictated by the point at which the tines  70  re-enter the intake duct at its lower end. Though this size is constant, the mass of crop that the tines have to displace is not constant and varies with the density of the pre-compressed crop material in the intake duct. This density varies with such factors as the type of crop material and the moisture content of the crop material. Further, because a stuffer cycle cannot be commenced at any time at will but has to be synchronised with the movement of the plunger, an excess of crop can be pre-compressed in the intake duct while waiting for the plunger to reach a point in its cycle at which the stuffer cycle can be triggered. 
     Aside from the variations in the mass of each slice resulting from variations in density, the force needed to push a slice of crop into the baling chamber is affected by the frictional forces between the crop and the surface of the intake duct  26 . A crop such as dry hay will thus exhibit much lower friction than, for example, wet grass. 
     For the reasons given above, despite best efforts being made to avoid blockages in the intake duct, such blockages do occur from time to time. A blockage will occur when the tines cannot exert enough force to push the slice of crop that has been pre-compressed in the intake duct up into the baling chamber. If excessive torque is applied to move the tines  70  against the resistance offered by the crop there is a risk of causing severe damage to the stuffer mechanism. Shear bolts are used to prevent such damage. When the loads exceed the shear force of the bolt, the stuffer is disconnected before its components are damaged. This situation is detected by the control unit of the baler and the operator is alerted of a detected blockage occurring in the intake duct. The shearbolt can be replaced relatively easy, but in certain cases it will not be possible to restart the normal operation of the baler as the stuffer unit will not be able to remove the crop material in the precompression chamber without activating the overload protection. In this case it will cost the operator valuable time to render the baler operable again, because it will be required to clear the intake duct  26  manually before the baler can be restarted. This is a job that requires extensive safety precautions and it is very difficult to gain access to the intake duct  26 . According to an alternative known embodiment there could be used overload clutches or other known means to prevent damage to the stuffer unit. They however suffer the same disadvantages as mentioned above. 
     The present invention is therefore concerned with the problem of how to clear such a blockage once it has been detected and the baler has been brought to a stop. Hitherto, clearing of a blockage in certain circumstances as mentioned above required gaining access to the interior of the duct  26  which, because of its being secured to the bale case at its upper end and having for example a packer  48  at its lower end, was not simple exercise. 
     The solution that the present invention proposes to solve this problem is to modify the mechanical linkage driving the tines to change the path  92  swept by the ends of the tines  70  in such a manner as to reduce the loading on the tines. Instead of attempting to load the entire contents of the intake duct  26  into the baling chamber in one cycle of the stuffer, only a fraction of the slice is loaded in a modified stuffer cycle. Furthermore during this partial loading cycle the speed and accelerations at which the tines  70  are moved along the intake duct are reduced which results in a reduced load on the stuffer. On return to its normal cycle the stuffer will then be able to cope with such crop as still remains in the intake duct without activating the overload protection or suffering any damage. 
     In the case of the linkage shown in  FIGS. 1 and 2 , the desired modification to the path of the tips of the tines  70  can be achieved by moving the position of the journals  88  nearer to the fixed pivot  96 . 
     The journals are not only closer, they are also rotated over a certain angle. This results in the tines following the path designated  92 ′ in  FIG. 2 . When following the path  92 ′, the tines  70  transfer a partial slice into the baling chamber because the tines enter the intake duct at a point further from the packer unit  48  and nearer to the inlet of the bale case. The shorter length slice will offer less resistance both because of its lower mass and reduced friction. Also, during this partial loading cycle the speed and accelerations at which the tines  70  are moved along the intake duct are reduced, as there is a shorter travel path to complete within the same timeslot, which results in a reduced load on the stuffer. This then allows the intake duct to be partially emptied without the need for it to be cleared manually and without risk of breaking the shear bolt of the stuffer mechanism. 
     When the journals  88  are then returned to their normal position the remaining crop material in the intake duct will be loaded into the baling chamber, again without risk of breaking the shear bolt of the stuffer mechanism. This can be performed by triggering a further cycle of the stuffer without picking up more crop material. Alternatively the crop remaining in the intake duct may simple form part of the next charge to be loaded into the baling chamber once normal operation is resumed. 
       FIGS. 3 to 5  show different ways in which the journals can be repositioned on the pivot plates. 
     In the embodiment of  FIG. 3 , the pivot plate  194  is intended as a direct replacement for the pivot plate  94  in  FIG. 2 . It is pivoted about a pivot  196  but instead of the journal  188  being mounted directly on the pivot plate  194  is mounted on a separate disc  112  that is secured to the plate  194  by bolts  114  passing through elongated slots  110  in the plate  194 . Loosening the bolts  114  and moving the disc to the right as viewed will result in the tines  70  tracing the path  92 ′ in  FIG. 2  instead of the path  92 . 
     In the embodiment of  FIG. 4 , the journal  288  is part of a lever arm  210  that is pivotable about a pivot  212  relative to the pivot plate  294  which is also inted as a direct replacement for pivot plate  94  and is pivoted about a pivot  296 . A bolt  216  acting on the lever arm  210  can reposition the lever arm  210  to cause the journal  288  to slide to the right as viewed along a guide slot  214  in the pivot plate  294 . 
     In the embodiment of  FIG. 5 , the journal  388  is formed as an eccentric on a circular disc  314  rotatable within a circular hole  310  in the pivot plate  394 . The disc  314  may be rotated by a radial arm  312  and features to retain the disc  314  in one of two preferred orientations such as for example a bolt  316  that interacts with an associated first hole in the pivot plate  394  and can interact with a second hole  318  in the pivot plate  394  when the radial arm  312  is repositioned. As an alternative, if the discs  310  are not circular, it is possible to swap the discs  310  on the opposite sides baler to reposition the journals  388  as required. 
     Though the above description has concentrated on the manner in which the geometry of the stuffer mechanical linkage taught by EP 0 636 308, it will be clear to the person skilled in the art that other stuffer drive systems, may be modified to reduce the length of intake duct swept by the tines of the stuffer during a stuffer cycle. For example, in GB 2197251, the pivot point of one of the arms connected to lever designated  13  of this patent may be repositioned when it is desired to clear a blockage by loading into the baling chamber only part of the slice accumulated in the intake duct. 
     The invention as defined in the claims is not limited to the exemplary embodiments that have been described and shown in the Figures, but it can equally comprise combinations and variations that fall within the scope of the claims.