Abstract:
A belt tensioning mechanism for use in a forage harvester comprises a cranking arm pivotable about a fixed axis between two positions and connected to move an idler roller into and out of contact with a belt to be tensioned. A plate rotatable with the cranking arm cooperates with a spring biased locked lever to lock the cranking arm in each of the two positions.

Description:
REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]     This Patent Application claims priority under 35 U.S.C. § 119 to GB 0423398.7, filed on Oct. 22, 2004, 2005, titled, “BELT TENSIONING MECHANISM”, the full disclosure of which is hereby fully incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a belt tensioning mechanism for use in a forage harvester and comprising a cranking arm pivotable about a fixed axis between two positions and connected to move an idler roller into and out of contact with a belt to be tensioned.  
       BACKGROUND OF THE INVENTION  
       [0003]     A forage harvester can be used with different crops, some with, and other without, kernels. As kernels are difficult for animals to digest, it is known to provide a kernel cracking device, sometimes also known as a crop processor, which can selectively be placed within and withdrawn from the crop flow path, to suit the crop being harvested (see for example EP-A-1358788). The crop processor typically comprises a pair of belt driven serrated rollers between which the crop is crushed. Because of the belt drive, withdrawal of the crop processor from the crop flow path requires removal of the drive belt and hitherto relieving the belt tension and removing the belt have proved to be difficult tasks for which tools were needed.  
         [0004]     The problem is aggravated by the little space available in a forage harvester to accommodate the drive belt. Further, drive pulleys of the crop processor place severe limitations one where a belt tensioning mechanism can be accommodated.  
         [0005]     Accordingly, the present invention seeks therefore to provide a belt tensioning mechanism that is sufficiently compact to enable it to be used in a forage harvester, yet which allows the belt tension to be released and reset rapidly without the need for special tools.  
       SUMMARY OF THE INVENTION  
       [0006]     According to the present invention, there is provided a belt tensioning mechanism comprising a cranking arm pivotable about a fixed axis between two positions and connected to move an idler roller into and out of contact with a belt to be tensioned, a plate rotatable with the cranking arm and a spring biased locking lever cooperating with the plate to lock the cranking arm in each of the said two positions.  
         [0007]     Conveniently, the idler roller is connected to a rod that is slidably connected to the cranking arm and at least one spring is provided to act between the cranking arm and a stop on the rod. In this way, the idler roller can be moved between two positions rapidly by rotating the cranking arm and in each of the two positions the cranking arm is firmly and securely locked.  
         [0008]     Preferably, the locking lever includes a projecting pin, which engages in a respective one of two holes formed in the locking plate when the cranking arm is in each of the two positions. Of course, it would be possible to provide alternative interlocking formations on the locking lever and the plate. A locking lever is provided in the present invention because considerable force is required to release the locking pin because it is the pin, or other interlocking formation, which provides the reaction force needed to maintain the belt in tension.  
         [0009]     Advantageously, the locking lever is pivotable about an axis that is coplanar with the axis of rotation of the cranking arm but extends transversely thereto. This makes for a particularly compact configuration. The stop on the rod may suitably be constituted by a nut in screw threaded engagement with the rod, the position of the nut along the rod being thereby adjustable to set the force applied by the idler roller to the belt to maintain the belt in tension.  
         [0010]     Because of the space limitations mentioned above, it may not be possible to make the cranking arm sufficiently long to enable the desired degree of belt tension to be applied by manually the turning the cranking lever. It is therefore desirable to provide the cranking arm with a connector to enable an extension lever to be attached to the cranking arm. The connector may for example be a simple tube welded to the cranking arm to receive the end of a crow bar or other convenient implement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:  
         [0012]      FIG. 1  is a side view of a belt tensioning mechanism of the invention with the belt tension released;  
         [0013]      FIG. 2  is a similar view to  FIG. 1  with the belt tension applied; and  
         [0014]      FIG. 3  is a perspective view from above of the belt tensioning lever mechanism for moving the rod connected to the idler roller.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]      FIGS. 1 and 2  show a drive belt  10  for a crop processor of a forage harvester which passes around four pulleys  12 ,  14 ,  16  and  18 . A fuller description of this belt drive is to be found in EP-A-1358788, referred to above, and a detailed explanation is not required in the present context as the invention can be applied to any belt drive in which it is desired to be able to release the belt tension and reset it rapidly without the use of special tools.  
         [0016]     In the case of the illustrated belt drive, it suffices to know that the pulley  18  is driven by the blower (not shown) of the forage harvester, pulley  12  is a first idler roller and pulleys  14  and  16  are drive pulleys mounted on the ends of the serrated rollers (not shown) of the crop processor. Tension in the belt  10  is maintained by a second idler roller  20  that is mounted on the end of a short pivotable arm  22  and is pulled against the belt  10  by the belt tensioning mechanism of the invention.  
         [0017]     As shown in  FIG. 3 , the belt tensioning mechanism includes a cranking arm  28  comprising a central hub  28   a  and two radially projecting cheeks  28   b  and  28   c  which carry between them a guide block  26  that can pivot relative to the cheeks  28   b  and  28   c  about pins  26   a . A rod  24  that is connected to the arm  22  (see  FIGS. 1 and 2 ) is slidably received in the guide block  26 . Two nuts  32  and  34  (see  FIGS. 1 and 2 ) that are threaded on to the rod  24  act as end stops for a strong spring  36  and a weaker spring  38  arranged on opposite sides of the guide block  26 .  
         [0018]     The cranking arm  28  is pivotably mounted on a stationary frame member  40  by means of a pin  42  passing through its hub  28   a . The cheek  28   b  has welded to it a short length of tube  44  which can act as a connector for an extension lever, such as a crow bar. The opposite cheek  28   c  is formed integrally with a plate  46  having two holes  48 . A locking lever  50  is pivotable relative to the frame member  40  about a pivot  52  of which the axis lies in the same plane as that of the pin  42  but at right angles to the latter axis. To one side of the pivot  52 , the locking lever  50  is acted upon by a spring mechanism  54  and on the opposite side it carries a pin  56  which can engage in the two holes  48  to lock the cranking arm in one of two positions.  
         [0019]     By inserting a lever into the connector  44 , the cranking arm can  28  be turned manually between the position shown in  FIG. 1  and that shown in  FIG. 2 . When the cranking arm  28  is turned counter-clockwise to engage the pin  56  in one of the holes  48  of the plate  46 , the belt drive adopts the configuration shown in  FIG. 1 . Here, the guide block  26  has moved to the right and the weak spring  38  acting on the stop  34  has moved the rod  24  to the right to disengage the idler roller  20  from the belt  10 . In this position, the belt  10  can be lifted off the various pulleys  12 ,  14 ,  16 ,  18 , and  20  to enable the crop processor to be removed. The weak spring  38  is required only to be able to apply the necessary force to pivot the idler roller  20  and the arm  22 .  
         [0020]     When the crop processor is re-introduced into the crop flow path, the belt  10  is rethreaded around the various pulleys  12 ,  14 ,  16 ,  18 , and  20 . To tension the belt  10 , the locking lever  50  is first pivoted about the pivot  52  (see  FIG. 3 ) to disengage the pin  56  (also see  FIG. 3 ) from the hole  48  in the plate  46 . With the pin  56  retracted from the hole  48 , the plate  46  and the cranking arm  28  can be rotated clockwise into the position shown in  FIG. 2 . An extension lever needs to be inserted in the connector  44  to allow sufficient torque to be applied to tension the belt  10 .  
         [0021]     When the cranking arm reaches the position shown in  FIG. 2 , the spring mechanism  54  (see  FIG. 3 ) acting on the lever  50  pivots it to engage the pin  56  (also see  FIG. 3 ) in the second hole  48 , in order to lock the cranking arm  28  in its new position. In this position, the guide block  26  has been moved to the left, as viewed, by the rotation of the cranking arm  28  and the spring  36 , which transmits a force to the rod  24  via the stop  32  to move the idler roller  20  into the belt tensioning position. The belt tension is controlled by the compression of the spring  36 , which can itself be adjusted by moving the nut  32  along the rod  24 . Once the position of the nut  32  has been set, the same degree of tension will be applied to the belt  10  whenever the cranking lever  28  is moved into the position shown in  FIG. 2 .  
         [0022]     It can thus be seen that the invention allows simple removal and replacement of the belt  10  without any special tools and ensures that the correct tension is applied to the belt  10  after it has been replaced. The entire operation can be carried out by single person who can turn the cranking arm  28  with one hand while releasing the locking lever  50  with the other. The length of the lever  50  simplifies the task of releasing the locking pin  56  and this operation is also made easier if the force on the pin  56  is reduced by turning the cranking arm  28  with the aid of the extension lever.