Abstract:
A tensioning system for a drive belt of a blower of a forage harvester, comprises a tensioning roller, a rod for moving the tensioning roller towards and away from the belt, a spring surrounding the rod and acting between a first abutment mounted on the rod and a second abutment connected to the chassis of the harvester to urge the roller towards the belt. The chassis connected abutment is carried by an arm that is movable relative to the chassis and anchored by means of a tie bar.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a belt tensioning system for a forage harvester.  
       BACKGROUND OF THE INVENTION  
       [0002]     Forage harvesters are machines which chop crop gathered from a field into small pieces to produce animal feed. In the case of crops such as grass or alfalfa, these will have been pre-cut and left to dry in the sun, so that the crop need only be gathered by the harvester. With other crops, such as maize, the forage harvester may also be required to cut the crop. Thus, the harvesters may be fitted with different headers to suit the crop being harvested.  
         [0003]     The crop, whether cut maize or gathered grass, is fed into a rotating knife drum or cutter which comminutes the product. With grass crops, this alone is sufficient to produce the desired forage. However, when harvesting maize for silage purposes, the cutting alone does not suffice due to the presence of kernels in the crop. The kernels need to be cracked in order to release the nutrient, as uncracked kernels are hard for animals to digest. As cutting alone is insufficient to crack all the kernels, the crop is additionally passed through a crop processor which comprises two closely adjacent rollers, typically having serrated surfaces, which rotate such that there is slippage between the adjacent surfaces. The gap between the rollers is set to suit the size of grain passing through and the speed, rotational energy of the rollers, relative movement and serration of the surfaces together ensure cracking of any kernels that are still intact after chopping by the cutter.  
         [0004]     The momentum of the maize from the crop processor or the grass from the cutter, as the case may be, carries the crop into a blower which then propels it up a tower to a discharge spout through which it is discharged into a wagon or a trailer drawn by a separate vehicle driven alongside the harvester.  
         [0005]     When chopping kernel-free crops, such as grass or alfalfa, the crop processor is not required and leaving it in place in the crop flow path results in its rollers being unnecessarily subjected to wear.  
         [0006]     To avoid such wear, it has previously been proposed to remove the crop processor from the vehicle, but the size and weight of the crop processor make this a difficult and cumbersome task.  
         [0007]     Another solution, disclosed in GB 2 414 373, is to pivot the crop processor away from its operative position in the crop path but to leave it on the vehicle in an inoperative position. In GB 2 414 373, in order to avoid blockages, the blower and the crop processor are connected to a common pivot frame so that as the crop processor is withdrawn from the crop flow path, the blower moves downwards to take its place.  
         [0008]     Because the drive pulley of the blower needs to move between two different positions, a tensioning roller is required for the belt which transmits drive to the blower from the engine and the present invention seeks to provide a suitable belt tensioning system that is simple to install and to set up correctly.  
       SUMMARY OF THE INVENTION  
       [0009]     According to the present invention, there is provided a tensioning system for a drive belt of a blower of a forage harvester, comprising a tensioning roller, a rod for moving the tensioning roller towards and away from the belt, a spring surrounding the rod and acting between a first abutment mounted on the rod and a second abutment connected to the chassis of the harvester to urge the roller towards the belt, characterised in that the abutment connected to the chassis is carried by an arm that is movable relative to the chassis and anchored by means of a tie bar.  
         [0010]     Preferably, the arm carrying the second abutment is pivotably mounted on the chassis of the harvester.  
         [0011]     In the preferred embodiment of the invention, the tie bar is of adjustable length to enable the belt to be loosened by varying the length of the tie bar.  
         [0012]     If the end of the tie bar remote from the pivotable arm is secured to the pivot frame that serves to mount the blower on the chassis of the harvester, then it is possible by suitable selection of the geometry of the pivotable arm and the tie bar to ensure that the drive belt of the blower is correctly tensioned in the different operative positions of the blower, so as to avoid the need for readjustment.  
         [0013]     It is desirable for the first abutment on the tensioning rod to be defined by a tube which is disposed within the spring and which surrounds and is in threaded engagement with the rod, the position of the first abutment being adjustable by rotating the tube relative to the tensioning rod.  
         [0014]     The second abutment is advantageously formed by a collar slidable over the outer surface of the tube and secured to the movable arm.  
         [0015]     Advantageously, a portion of the tube extending beyond the slidable collar is externally screw threaded and engaged by a nut to enable the spring to be held in compression on the tube prior to the tube being fitted as a sub-assembly over the tensioning rod.  
         [0016]     The invention further provides a method for tensioning a belt by using a tensioning system as set forth above, which comprises the steps of mounting the rod and the spring between the movable arm and the tensioning roller, moving the arm by varying the length of the tie bar and simultaneously placing the tensioning roller onto the belt to achieve an initial setting of the spring tension to the belt and moving the first abutment on the rod relative to the second abutment on the movable arm while simultaneously moving the rod with the tensioning roller to the belt to achieve a final setting of the spring tension by the tensioning roller to the belt.  
         [0017]     The invention further provides a method for releasing the tension on a belt by using a tensioning system as set forth in claim  7  of the appended claims, which comprises the steps of moving the second abutment on the movable arm relative to the first abutment until the second abutment contacts the nut by varying the length of the tie bar and moving the arm together with the rod, the spring and tensioning roller by continuing to vary the length of the tie bar.  
         [0018]     In the preferred embodiment of the invention, an element may be placed between the second abutment and a washer of the nut to limit the distance over which the tie bar needs to be varied against the force of the spring.  
         [0019]     The invention further provides a method for re-tensioning the tension on a belt by using a tensioning system as set forth above which comprises the steps of moving the arm together with the rod, pre-assembly unit and tensioning roller by varying the length of the tie bar, and moving the second abutment on the movable arm relative to the first abutment by a continued varying of the length of the tie bar until the position of the tensioning roller on the belt prior to releasing is attained. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:  
         [0021]      FIG. 1  is a schematic representation of a belt driving the blower of a forage harvester and tensioned by a tensioning system of the invention,  
         [0022]      FIG. 2  is a section through the tensioning rod and spring of a belt tensioning system of the invention,  
         [0023]      FIG. 3  shows a perspective view from one side of the belt tensioning system of  FIG. 2 ,  
         [0024]      FIG. 4  is a partial perspective view from the other side of the belt tensioning system of  FIGS. 2 and 3 ,  
         [0025]      FIG. 5  is a section along the line V-V in  FIG. 2 , and  
         [0026]      FIG. 6  shows the detail of  FIG. 2  within the chain-dotted frame  70  drawn to an enlarged scale. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]      FIG. 1  shows part of the chassis  10  of a forage harvester on which there is mounted an engine driving a pulley  12 , a cutter driven by a pulley  14  and a blower driven by a pulley  16 . The engine, cutter and blower are not shown in the drawing but reference may be made to GB 2 414 373 for a fuller description of the harvester.  
         [0028]     The blower and the cutter are driven by a belt  18  which also passes over an idler roller  20  and a tensioning roller  22 . Because the blower pulley  16  can move between two different positions (for the reasons explained previously), a tensioning system  24  is required that is capable of maintaining the belt  18  correctly tensioned in both positions of the pulley  16  and when the blower and pulley  16  are moving between these two positions.  
         [0029]     The tensioning system of the invention is shown in greater detail in FIGS.  2  to  6 . The roller  22  is mounted on the end of a spring biased tensioning rod  34 . The rod  34  carries a first abutment  36  for a spring  40  which surrounds the rod  34 . The other end of the spring  40  acts against a second abutment  42  which is connected to the chassis  10  of the forage harvester.  
         [0030]     Conventionally, the second abutment cannot move relative to the chassis and installation involves fitting the spring over the rod, adjusting the position of the rod in the second abutment and the position of the abutment on the rod until the desired tension is achieved. This is a very tiring and time consuming procedure and requires space for the tools needed to achieve the correct tensioning.  
         [0031]     In the illustrated embodiment of the invention, the second abutment is formed by a collar  42  mounted on an arm  26  which is pivoted about a pin  28  relative to the chassis  10 . The collar  42  lies on one side of the arm  26  and its other side is secured by a tie bar  30  of adjustable length to a pin  32  mounted on the pivot frame carrying the blower. The tie bar  30  is formed by two parts in threaded engagement with one another, so that its length can be adjusted by turning a nut  31 .  
         [0032]     The abutment  36  is defined by a flange at the end of a tube  38  which surrounds the tensioning rod  34 . The tube  38  has inserts at each of its two ends, the abutment  36  may be formed by a flange of one of these two inserts, which is in threaded engagement with the tensioning rod  34 .  
         [0033]     The insert  44  at the opposite end of the tube  38 , as more clearly shown in  FIG. 6 , has a head  44   a  which is hexagonal to enable it to be gripped by means of a spanner. Beyond the hexagonal head  44   a  there is a sleeve  44   b  which is threaded both internally and externally. A locknut  48  serves to prevent rotation of the sleeve  44   b  and with it the tube  38  relative to the rod  34  once the spring tension has been correctly set. A second nut and washer  46  screwed onto the external thread of the sleeve  44   b  serve as an end stop to allow the spring  40  to be retained and tensioned about the tube  38  prior to its installation over the rod  34 . This allows the spring  40  and tube  38  to be fitted as a sub-assembly over the rod  34 , thus saving time and effort during the installation.  
         [0034]     The collar  42  that acts as the second abutment for the spring  40 , is constructed as swivel that is free to pivot about pins  42   a  (see  FIG. 5 ) between two plates  60  and  62  mounted on rods  64  and  65  that project laterally from the pivotable arm  26 . The plate  60  is removable to allow the collar  42  to be secured to and separated from the pivotable arm  26 . The tie bar  30  is held in a similar manner in a swivel on the opposite side of the pivotable arm  26  and is connected through the pivotable arm  26  to the collar  42  by means of rod  64 .  FIG. 5  also shows that when installed in a forage harvester, a panel  68  of the harvester separates the arm  26  from the tensioning rod  34 , the two rods  64  and  65  passing through arcuate slots in the panel  68 .  
         [0035]     At the commencement of assembly, the tie bar  30 , while connected to the pivot frame of the blower, is extended to its maximum length so that the arm  26  is rotated clockwise in  FIG. 2 . A pre-assembly comprising the tube  38 , the collar  42 , the first abutment  36 , the insert  44 , the nut with washer  46  and the spring  40 , is next placed over the end of the tensioning rod  34  remote from the roller  22 . The pre-assembly unit is screwed onto the tensioning rod  34  and secured by locknut  48 . The length of the rod  34  projecting from the tube  38  is set so that the collar  42  aligns with the hole in the plate  62 . The plate  60  is then bolted to the rods  64  and  65  to secure the collar  42  to the arm  26  and tie bar  30 .  
         [0036]     Next, the nut  31  is rotated to shorten the tie bar  30  and cause the arm  26  to pivot about the pin  28 , in a counter clockwise direction as viewed in  FIG. 2  thus moving the tensioning arm with collar  42  towards the belt  18 . As the arm  26  pivots, the collar  42  slides over the outer surface of the tube  38  and compresses the spring  40  between itself and the first abutment  36  defined by the flange of the insert at the opposite end of the tube  38 . The length of the tie bar  30  is chosen so that when the two parts of the tie bar are turned in completely and thus the tie bar is at its minimum length, the hexagonal head  44   a  of the insert  44  becomes accessible. Fully tensioning the belt  18  by the tensioning roller  22  is achieved by rotating the tube  38  relative to the tensioning rod  34 . When the locknut  48  is loosened, the-tube  38  may be turned by gripping the hexagonal head  44   a  thus moving the tensioning rod  34  with the tensioning roller towards the belt  18  while the tube  38  is being turned inside the threaded first abutment  36 . After the correct setting has been achieved, the locknut  48  is tightened again to retain the setting.  
         [0037]     Because the tie bar  30  is anchored to the pivot frame of the blower, the point  32  will move when the blower is repositioned and by suitable selection of the geometry of the tie bar  30  and the pivoting arm  26  it is possible to ensure that the belt tension will remain correctly set in both positions of the blower.  
         [0038]     Removing the tensioning roller  22  from the belt  18  for any reason, can be done by only loosening nut  31  and varying the length of the tie bar  30 . When the nut  31  is turned, the arm  26  will move clockwise around pin  28  thus moving the collar  42  because of their connections through rods  64  and  65 . However, this turning of the nut  31  needs to be against the tension of the spring  40  and this entails a large effort. To simplify the task, a U-shaped spacer  80  (see  FIGS. 4 and 6 ) can be slipped over the tube  38  to bridge a large part of the gap between the collar  42  and the stop but  46  before the nut  31  is undone. Only a limited distance over which the nut  31  needs to be turned against the force of the spring  40  remains. Once the spacer is firmly wedged between the stop nut  46  and the collar  42 , undoing the nut is no longer against the force of the spring. When further undoing the nut  31 , the complete tensioning system  24  will move away from the belt by rotating about pin  28  without changing the relative distance between the first abutment  36  and the collar  42 .  
         [0039]     Re-assembly then merely requires repositioning the tensioning roller  22  by turning the nut  31  and shortening the length of the tie bar  30 . The complete tensioning system  24  will then move towards the belt. Only the last distance over which the tie bar  30  needs to be shortened will be against the force of the spring. Once the U-shaped spacer  80  is no longer wedged between the collar  42  and washer of the nut  46 , the collar  42  will be moved towards the first abutment  36  together with the shortening tie bar  30 . Once the tie bar  30  is again in its shortest position, the tensioning of the belt is complete. In this way, the tensioning system can be removed and replaced quickly and as long as the tie bar  30  is shortened to its original length, the tension setting will not be affected and will not require adjustment. When not in use, the U-shaped spaced  80  can be secured to the arm  26  in a storage position, as shown in  FIGS. 3 and 5 .  
         [0040]     If the tensioning system  24  needs to be dismantled for any reason, it would be possible to reverse the above steps and to remove the pre-assembly unit from between the plates  60  and  62 . The complete installation and tensioning the belt by the tensioning system needs to be done by using the variable tie bar  30  and the hexagon  44   a.