Patent Publication Number: US-2023141904-A1

Title: Easy adjust tensioner assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is continuation of U.S. patent application Ser. No. 16/955,232, filed Jun. 18, 2020, which is a national phase entry under 35 U.S.C. § 371 of International Patent Application PCT/IB2018/057893, filed Oct. 11, 2018, designating the United States of America and published in English as International Patent Publication WO 2019/123032 A1 on Jun. 27, 2019, which claimed the benefit of the filing date of U.S. Provisional Patent Application 62/612,776, “Easy Adjust Tensioner Assembly,” filed Jan. 2, 2018; and U.K. Patent Application 1721786.0, filed Dec. 22, 2017, “Easy Adjust Tensioner Assembly; the entire disclosure of each of which is incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to a tensioner bar apparatus. In particular, the invention relates to a tensioner bar apparatus for use with a tensioner arm for a drive belt. Such a drive belt may typically be found in an agricultural apparatus, such as a combine harvester or other agricultural machine. 
     BACKGROUND 
     Combine harvesters and other agricultural machines commonly contain a number of drive systems comprising a belt or chain to transfer power from a drive source to a driven power consuming system. Such belts or chains are often provided with a means for tensioning or taking up slack in the belt or chain in the drive system. 
       FIG.  1    shows a typical drive system  60  from a combine harvester. The drive system  60  provides drive power to a straw chopper at the rear end of a combine harvester. 
     The drive system  60  comprises a driving wheel  61  and a driven wheel  62  connected by a belt  63 . Tension in the belt  63  is applied by an idler wheel  47 , which presses against the belt  63  and is mounted on a tensioning arm  41 . 
     The idler wheel  47  is rotationally mounted on a first end  41   a  of the tensioning arm  41 , and the tensioning arm  41  is pivotally mounted, at a midpoint  41   m,  to the combine harvester. To the second end  41   b  of the tensioning arm is connected a tensioning bar assembly  11 , which applies a tensioning force Fa. 
     The tensioning bar assembly  11  comprises a longitudinal bar  2 . At a first, or ‘top’ end  2   t  of the bar  2  is a clevis assembly  3 , which is connected to the second end  41   b  of the tensioning arm  41  by a clevis pin  36 . In this prior art arrangement, the longitudinal bar  2  is rotationally fixed to the clevis assembly  3  such that in effect the bar  2  and clevis assembly  3  are a unitary item. A portion  2   a  of the bar  2  has a screw thread. Fitted over this threaded portion  2   a  of the bar  2  is a spring  4   s,  provided with a top retainer  4   t  and a bottom retainer  4   b,  which together keep the spring  4   s  in place. 
     When in position on the machine, the top retainer  4   t  butts up against a bracket  20  attached to the combine harvester. The bottom retainer  4   b  is kept in its position on the bar  2  by a pair of locking nuts  5   a,    5   b  fitted onto the screw thread—a first locking nut  5   a  for adjustment of spring compression and the second locking nut  5   b  for locking the first locking nut  5   a  in place. 
     When in position on the machine, the spring  4   s  is effectively compressed between the bracket  20  and the locking nuts  5   a,    5   b  via the action of the top and bottom retainers  4   t,    4   b,  respectively. The action of the spring  4   s  on the top retainer  4   t,  and thus the bracket  20 , acts to ‘push’ the bottom retainer  4   b,  and thus the locking nuts  5   a,    5   b,  away from the bracket  20 . As the locking nuts  5   a,    5   b  are threaded onto the longitudinal bar  2 , this provides an axial force Fa along the bar  2  which in turn, through the clevis  3  and clevis pin  36 , produces a sustained force on the second end  41   b  of the tensioning arm  41 . As the tensioning arm  41  is pivotally mounted at a midpoint  41   m,  this produces a torque around the pivot point  41   p,  such that the idler wheel  47 , mounted on the first end  41   a  of the tensioning arm  41 , is pressed against the belt  63  and thus provides a tensioning force Ft on the belt  63 . 
     It is occasionally necessary to adjust the tensioning bar assembly  11 , either to change the spring tension or to replace worn or broken components. To do this, when the tensioning bar assembly  11  is in position, it is necessary first to loosen the second locking nut  5   b.  This releases the first locking nut  5   a  to be rotated around, and thus move along, the threaded portion  2   a  of the longitudinal bar  2 , changing the axial position of the bottom retainer  4   b  and thus adjusting the spring compression (and hence the force with which the spring  4   s  acts against the bracket  20  and consequently, via the longitudinal bar  2 , tensioning arm  41  and idler wheel  47 , the tensioning force Ft with which the idler wheel  47  contacts the belt  63 ). This requires a wrench or spanner, such as an open end wrench/spanner or ratcheting wrench/spanner. 
     Use of such a wrench or spanner requires the involvement of an operator, and this is a job which is typically tedious and consumes an undesirable amount of time and energy. Further, machines such as a combine harvester, and indeed many other agricultural machines, are typically complex machines with many other components in close proximity to the drive system. Access to the locking nuts  5   a,    5   b,  where an access route is typically required to be substantially perpendicular to the axis of the longitudinal bar  2  when a wrench is used, is therefore not always straightforward, further making the adjustment process problematic. Space is also required to allow for rotational movement of the wrench or spanner around the longitudinal bar  2  so as to rotate the nuts  5   a,    5   b  on the threaded portion  2   a.  This is particularly challenging when the first part of the operation, namely loosening the second locking nut  5   b,  may require the use of two wrenches (spanners), due to tightness of the engagement of the locking nuts  5   a,    5   b —one wrench to hold the first locking nut  5   a  stationary and provide a reactive torque against the torque applied by a second wrench being used to loosen the second locking nut  5   b.  Thus, access is typically required for two wrenches. A solution to these problems would be desirable. 
     BRIEF SUMMARY 
     In some embodiments, a tensioning bar assembly  111  for a tensioning assembly  101  of a drive system  60  of an agricultural machine includes a longitudinal bar  102  having a longitudinal axis  102   x,  a top end  102   t  and a bottom end  102   b  and a threaded portion  102   a  over at least a portion of the bar; an attachment device  103  coupled to the top end of the longitudinal bar for attaching the top end of the bar to a tensioning arm  41 ; a compression spring  4   s  having first  6   b  and second  6   t  ends and located around a portion of the longitudinal bar; a first spring retainer  4   b  for engaging with and retaining the first end  6   b  of the spring; a first locking nut  5   a  for fitting to the threaded portion  102   a  of the bar and for retaining the first spring retainer longitudinally in place relative to the bar. The longitudinal bar is rotationally freely coupled to the attachment device  103  to permit free axial rotation of the bar about the longitudinal axis  102   x  relative to the attachment device. An engagement head  102   h,    302   h  is attached to and located at or proximate the bottom end  102   b  of the longitudinal bar  102 . The engagement head is configured for engagement with a tool. 
     An advantage of this tensioning bar assembly is that the adjustment of the tensioning bar assembly may be performed by using a single wrench to hold the locking nut rotationally stationary relative to the longitudinal axis of the bar, and a second tool can then be used to engage with the engagement head attached to the bottom end of the bar. The bar itself can be rotated by the second tool, resulting in a rotational motion of the bar relative to the locking nut and hence altering the longitudinal placement of the locking nut on the threaded portion of the bar. Usefully, the engagement head may not require the use of an open end wrench and may be provided with a head for engagement with a complementary socket, or alternatively a socket for engagement with a complementary head, or similar mechanical arrangement, which complementary head or socket may also be attached to a power tool of some kind, such as a pneumatic socket gun or power screwdriver. This would make the adjustment of the tensioning assembly easier and also potentially a great deal quicker, as well as greatly reducing the physical exertion required by a user. 
     In an embodiment, the tensioning bar assembly further comprises a second spring retainer for engaging with and retaining the second end of the spring. 
     As will be described below, when in use the tensioning bar assembly will be fitted to a bracket and a tensioning arm. In some embodiments, the second end of the spring may directly contact the bracket, but in other embodiments the bar assembly is provided with a second spring retainer which is formed to ‘cup’ the end of the spring. This second spring retainer either butts up against or is connected to the bracket. 
     The first spring retainer is nominally kept in place longitudinally on the bar by the first locking nut. When the tensioner bar assembly is in place, the first spring retainer is pushed against the locking nut by the force of the spring. 
     In an embodiment, the first spring retainer and the first locking nut may be a unitary item, i.e., may be formed in one piece. 
     If the first spring retainer and first locking nut are a unitary item, then engagement of the spring with the first spring retainer may be more easily facilitated, because perpendicular motion of the first spring retainer will be prohibited due to its engagement with the threaded portion of the bar. It will also further facilitate the adjustment of the tensioner bar assembly. 
     In an embodiment, the bar assembly may be provided with a second locking nut, fitted adjacent to the first locking nut on the threaded portion of the bar, in order to ‘lock’ the first locking nut in place. 
     A second locking nut may be provided so as to assist in ‘locking’ the first locking nut, or, where there is a unitary first spring retainer/locking nut, the unitary item, axially in place on the threaded portion of the bar. 
     In some embodiments, the engagement head at or proximate the bottom end of the bar may be any one or more of: a triangle, square, pentagon or hex head or socket; a posidrive head or socket; a torx head or socket; a slotted or phillips screwdriver receiving socket; a spline head or socket; a pair of locking nuts locked in position on the threaded portion, proximate the bottom end of the bar; or an engagement head device screwed to the bottom end of the bar on the threaded portion, optionally locked in place with a locking nut  5   c.    
     The engagement head at or proximate the bottom end of the longitudinal bar has the purpose of allowing a tool to be applied to the longitudinal bar at a convenient point, and advantageously allows access to the engagement head in a longitudinal direction. Any shape of head may be used that allows for engagement with a tool. In some embodiments, a power tool may be used. The bottom end of the bar may therefore have any head or socket or other shape that allows engagement with a tool, and in addition to those already listed this may include any one of a head or socket such as Security Torx, Tri-wing, Spanner, Clutch, Mortorq, Frearson, Supadriv, Polydrive, Double square, Bristol, Torq-set, One-way, Pentalobe, TP3, or TTAP head, or indeed any other suitable geometry. The bar may be manufactured with such a head or socket in place as a unitary item with the bar. In a variant, the threaded portion of the bar may extend entirely to the bottom end of the bar, and a suitable head may be attached to the bottom end of the bar and locked in place with a locking nut. In a further variant, a hole may be present across a diameter of the bar, proximate to the bottom end, into which a pin may be inserted, and this pin may be engaged by a suitable tool. 
     In an embodiment, the top end  2   t  of the longitudinal bar  2  is located through a hole  34  in a portion  31  of the attachment device  3  and is retained in place by means of snap ring(s) or circlip(s)  21   c,    22   c  located in groove(s)  21 ,  22  proximate the top end of the bar. In another embodiment, the attachment device is a clevis. 
     Axial rotation of the longitudinal bar relative to the clevis (or other attachment device), while the longitudinal bar is retained in the clevis may be achieved by provision of a hole, such as a circular hole, in a body of the clevis or device. The longitudinal bar generally has a round cross-section, and the top end of the bar may be inserted into and through the hole. This allows the axial rotation of the bar relative to the device/clevis. Longitudinal restriction of the bar relative to the body of the device may be achieved by a circular groove around the diameter of the bar at a point proximate the top end of the bar, into which a snap ring or circlip may be fitted. In a variant, two such circular grooves may be provided so that a snap ring or circlip may be fitted to the bar on either side of the portion of the bar which penetrates the device, thus preventing axial movement of the bar relative to the device in either longitudinal direction. 
     Alternatives to the clevis may be used as an attachment device, such as an L-shaped bracket with a hole in either arm, a rod, bar or plate with a hole for attaching to a pivot point and a piece of hollow tubing attached thereto for receiving the bar, or any one of a number of other equivalent items. However, in the art a clevis is generally used and for ease of reference herein a clevis may generally be referred to although any suitable alternative will be generally intended to be encompassed by such reference. 
     In an embodiment, a tensioning assembly  101  for a drive system includes a tensioning bar assembly  111  as described elsewhere herein, and further comprising a tensioning arm  41  pivotally mounted  41   p  to the machine; a tensioning device  47  mounted to the tensioning arm for contacting the drive system  60 ,  63  and applying a tensioning force Ft directly thereto; and a bracket  20  mounted to the machine. The attachment device  3  is attached to the tensioning arm  41  at an attachment point  41   b,    41   m,    3   p  and the second end of the spring  6   t  is in direct or indirect physical contact with the bracket  20 . Compression of the spring applied by and between the bracket  20  and the first spring retainer  4   b  provides a resultant force Fa applied to the tensioning arm, via the attachment point  41   b,    41   m,    3   p,  about the pivot mounting point  41   p  of the tensioning arm, which produces the tensioning force Ft to force the tensioning device  47  into contact against the drive system  63 . 
     The attachment point, where the clevis is attached to the tensioning arm, may usefully be a pivot mount where a clevis pin is inserted through holes in arms of the clevis and also through a hole in the tensioning arm. Clevis pins, threaded clevis pins, and alternatives therefor (such as a bolt-and-nut arrangement) are standard items well known to those skilled in the art, and any suitable pin or alternative may be used. Compression of the spring may be achieved by placing the second end of the spring against the bracket, attaching the clevis to the clevis attachment point, and then adjusting the first locking nut (via the method enabled by the main aspect of the invention) so as to move the first locking nut, and hence the first spring retainer towards the bracket, thus resulting in a compression of the spring. The spring thus produces a force which acts substantially longitudinally along the axis of the bar, either to pull the clevis attachment point towards the bracket, or, depending on the arrangement of the spring relative to the bracket and the arrangement of the tensioning arm, to push the clevis attachment point away from the bracket. In some embodiments, the bracket is provided with a hole through which the bar of the bar assembly is fitted. In such embodiments, the second end of the spring is placed against a second spring retainer, which is in turn placed against or connected to the bracket. Possible variations are described further in the embodiments below. 
     In embodiments, the bracket has a facing side  20   f  facing towards the tensioning arm and a distal side  20   d  facing away from the tensioning arm; the spring  4   s,  first retainer  4   b,  and first locking nut  5   a  are located on the distal side; and the second end of the spring  6   t  is in direct or indirect physical contact with the distal side  20   d  of the bracket such that the resultant force Fa acts to pull the attachment point  103   p  towards the bracket. 
     In embodiments, the bracket has a facing side  20   f  facing towards the tensioning arm and a distal side  20   d  facing away from the tensioning arm; the spring  4   s,  first retainer  4   b,  and first locking nut  5   a  are located on the facing side; and the second end of the spring  6   t  is in direct or indirect physical contact with the facing side of the bracket such that the resultant force acts to push the attachment point  103   p  away from the bracket. 
     In embodiments, the tensioning arm  41  has a first end  41   a  and a second end  41   b,  the tensioning device  47  being mounted proximate to the first end  41   a,  the attachment point  103   p  being proximate to the second end  41  b, and the pivotal mounting  41   p  of the tensioning arm being at a midpoint  41   m  between the first and second ends. 
     In embodiments, the tensioning arm  241 ,  341  has a first end  41   a  and a second end  241   b,    341   b,  the tensioning device  47  being mounted proximate to the first end  41   a,  the pivotal mounting  241  p,  341   p  of the tensioning arm being proximate to the second end  241   b,    341   b,  and the attachment point  103   p  being at a midpoint  241   m,    341   m  between the first and second ends. 
     The second end of the spring may act directly against the bracket, or may act on a second spring retainer which in turn acts upon the bracket. The bracket may comprise a dish or annular groove which acts as a second spring retainer. The longitudinal bar may be positioned so that it passes through a hole or notch in the bracket, and/or may be positioned so that it passes through a hole or a notch in the second spring retainer. The second spring retainer may comprise a hole or notch through which the longitudinal bar passes, and may be attached by an arm so that the spring is laterally displaced from the bracket, as in  FIG.  4   c   . The attachment may be by screws, rivets, a simple clamp, or by any other means generally known in the art, such as nut/bolt combination  27  shown in  FIG.  4     c.    
     The tensioning device may be any suitable device for pressing against the drive system of the machine. 
     The drive system may be a belt drive or may be a chain drive. In either case, the tensioning device may be an idler wheel, roller, or may be a simple bar. Where the drive system is a chain drive, the tensioning device may equally be an idler gear with teeth that engage the chain. 
     In some embodiments, there is provided a drive system comprising a tensioning arm assembly or tensioning assembly as described herein. 
     In some embodiments, there is provided an agricultural machine comprising a tensioning bar assembly, tensioning assembly or drive system as described herein. 
     In an embodiment, an agricultural machine may be a combine harvester. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in more detail by reference to the attached figures. 
         FIG.  1    shows a typical prior art drive system from a combine harvester. It shows a drive system which provides drive power to a straw chopper at the rear end of a combine harvester and which has a tensioning assembly comprising a tensioning arm and a tensioning bar assembly. 
         FIG.  2    shows a cross-sectional view through a portion of the prior art tensioning assembly of  FIG.  1    in more detail. 
         FIG.  3    shows a diagrammatic view of elements of a tensioning bar assembly. 
         FIG.  3   a    shows a diagrammatic cross-sectional view of a clevis assembly. 
         FIG.  3   b    shows a diagrammatic partial view of an end of the bar assembly as shown in  FIGS.  3  and  3     a . 
         FIGS.  4   a ,  4   b , and  4   c    show schematic alternative arrangements of bar assembly, bracket, and tensioner arm. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1   , as described elsewhere herein, and  FIG.  2    show: 
     The drive system  60  comprises a driving wheel  61  and a driven wheel  62  connected by a belt  63 . Tension in the belt  63  is applied by a tensioning assembly  1 . Tensioning assembly  1  includes an idler wheel  47  which presses against the belt  63  with force Ft and is rotationally mounted on a tensioning arm  41  at a first end  41   a  of the tensioning arm  41 . 
     The tensioning arm  41  is pivotally mounted on a pivot  41   p,  at a midpoint  41   m,  to a combine harvester (not shown). To the second end  41   b  of the tensioning arm  41   b  is connected to a tensioning bar assembly  11 , which applies a force Fa to the end  41   b  of the arm  41 . 
     The tensioning bar assembly  11  comprises a longitudinal bar  2 . At a first, or ‘top’ end  2   t  of the bar  2  is a clevis assembly  3  which is connected to the second end  41   b  of the tensioning arm  41  by a clevis pin  36  at an attachment point  3   p.  In this prior art arrangement, the longitudinal bar  2  is fixed to the clevis assembly  3  such that in effect the bar  2  and clevis  3  are a unitary item. A portion  2   a  of the bar  2  has a screw thread. Fitted over this threaded portion  2   a  of the bar  2  is a spring  4   s,  having first end  6   b  and second end  6   t,  and also a first spring retainer  4   b  and a second spring retainer  4   t  which together keep the spring  4   s  in place. 
     When in position on a combine harvester (or other machine), the second spring retainer  4   t  butts up against bracket  20  which is attached, ultimately, to the combine harvester. In  FIG.  2   , spring retainer  4   t  has a generally curved top surface which locates in a generally curved recess on the distal side  20   d  of bracket  20 , which allows a degree of freedom of movement. Bar  2  fits through a hole provided in bracket  20 . Bracket  20  has a facing side  20   f  facing towards the tensioning arm  41  and a distal face  20   d  facing away from the tensioning arm. The first spring retainer  4   b  is kept in its position on the bar by a pair of locking nuts  5   a,    5   b  fitted onto the screw thread of bar portion  2   a  — a first locking nut  5   a  for adjustment of spring compression and the second locking nut  5   b  for locking the nuts in place. 
     When in position on the machine, the spring  4   s  is effectively compressed between the distal side  20   d  of bracket  20  and the locking nuts  5   a,    5   b  via the action of the top and bottom (second and first) retainers  4   t,    4   b  on ends of the spring  6   t,    6   b  respectively. The action of the spring  4   s  on the second retainer  4   t,  and thus the bracket face  20   d,  acts to ‘push’ the first retainer  4   b,  and thus the locking nuts  5   a,    5   b,  away from the bracket  20 . As the locking nuts  5   a,    5   b  are threaded onto and thus mechanically joined to the longitudinal bar  2 , this provides an axial force Fa along the bar  2  which in turn, through the clevis  3  and clevis pin  36  at the attachment point  3   p,  produces a sustained pulling force on the second end  41   b  of the tensioning arm  41 . As the tensioning arm  41  is pivotally mounted at a midpoint  41   m  of the arm  41 , this produces a torque T around the pivot point  41   p,  such that the idler wheel  47 , mounted on the first end  41   a  of the tensioning arm  41 , is pressed against the belt  63  and thus provides a tensioning force Ft on the belt  63 . 
       FIG.  3    shows a tensioning bar assembly  111  for use as a replacement for the prior art tensioning bar assembly  11  shown in  FIGS.  1  and  2   . 
     A longitudinal bar  102  has a first or top end  102   t  and a threaded portion  102   a  that extends from roughly a mid-point of the bar  102  to a second, or bottom end  102   b  of the bar  102 . A portion of the bottom end  102   b  of the bar  102  is formed into a hex head  102   h  so that a tool can be applied to it. Spring  4   s  with ends  6   b  and  6   t  and first and second spring retainers  4   b  and  4   t  are fitted around the threaded portion  102   a  of the bar  102 . First and second locking nuts  5   a  and  5   b  are also threaded on to portion  102   a  of the bar  102 , adjacent the first spring retainer  4   b.  At the top end  102   t  of the bar  102  is affixed a clevis assembly  103 , shown in more detail in  FIG.  3     a.    
       FIG.  3   a    shows that the clevis  103  has a main body  131  and arms  132 . The main body  131  has a hole  134  through which top end  102   t  of bar  102  may slidingly fit. Hole  134  and bar  102  are circular in cross-section so that bar  102  may freely rotate within the hole  134  about longitudinal axis  102   x.  Each of the arms  132  is also provided with a hole  135  through which a clevis pin  36  may be fitted. In  FIG.  3   , it can be seen that clevis pin  36  is further fitted with a circlip  37 . The top end of the bar  102   t  is provided with grooves  121  and  122 , seen clearly in  FIG.  3   b   , into which circlips  121   c  and  122   c  may be fitted as seen in  FIGS.  3  and  3     a . Depending on the fitment of the longitudinal bar assembly as part of the tensioning assembly, only one or other of the groove/circlip combinations may be required. For example, if the bar assembly is to provide a force Fa which pulls on the pivot point  3   p,  then only circlip  121   c  is strictly necessary. Likewise if the bar  102  is arranged to push on pivot point  3   p,  only circlip  122   c  may be required. 
     As described hereinbefore, the arrangement shown in  FIGS.  3 ,  3     a  and  3   b  allows for the simple adjustment of the tensioning assembly by engaging a tool at locking nut  5   a,  which can then be held stationary while the bar  102  is rotated by application of another tool to the hex head  102   h,  thus rotationally moving bar  102  relative to nut  5   a  and hence moving nut  5   a  along the bar. Locking nut  5   b  can similarly be moved along the bar until it butts up against nut  5   a,  locking it in position. A final operation with wrenches on both nuts  5   a  and  5   b  may fully lock the nuts together. 
       FIG.  4   a    shows an alternative embodiment of tensioning assembly  101  where a tensioning bar assembly  111  is arranged as part of a tensioning assembly  101  where the tensioning bar assembly  111  is located the other side of the tensioning arm  41  than in the arrangement of prior art  FIG.  1   . In this arrangement, tensioning force Fa is a pushing force on tensioning arm  41  due to the placement of the spring  4   s,  retainers ( 4   b,    4   t ) and a locking nut  5   a  on the facing side  20   f  of the bracket  20 . This results in the same torque T about pivot point  41   p  and tensioning force Ft as illustrated in  FIG.  1   , albeit with a different placement of elements of the tensioning assembly. 
       FIG.  4   b    shows an alternative embodiment where force Fa from tensioning bar assembly  111  is a pushing force on tensioning arm  241  due to the placement of the spring  4   s,  a retainer  4   b  and nut  5   a  on the facing side  20   f  of the bracket  20 . In this embodiment, arm  241  is pivotally mounted  241   p  at its second end  241   b  and clevis  103  is mounted via pin  103   p  to a midpoint  241   m  of the arm  241 . Pushing force Fa again results in a torque T about pivot point  241   p  which provides a tensioning force Ft on the belt  63 . In this embodiment, it is also notable that second end  6   t  of spring  4   s  acts directly against the face  20   f  of the bracket  20  and there is no retainer  4   t.    
       FIG.  4   c    shows an alternative embodiment where force Fa is a pulling force on tensioning arm  341  and tensioning arm  341  is pivoted about its second end  341   b  with clevis  103  attached to a midpoint  341   m.  In this embodiment, spring retainer  304   t  has an arm  304   ta  which is bolted by nut and bolt assembly  27  to bracket  20 . In this way, the spring  4   s  acts indirectly against the distal face  20   d  of the bracket  20 . Also in this embodiment is shown a head  302   h  which has been screwed on to the end  102   b  of bar  102 , then locked in place with a locking nut  5   c.    
     In summary there is disclosed a tensioning bar assembly  111  for a tensioning assembly  101  of a drive system  60  of an agricultural machine. A longitudinal bar  102  has a longitudinal axis  102   x,  a top end  102   t,  a bottom end  102   b,  and a threaded portion  102   a  over at least a portion of the bar. An attachment device  103  is coupled to the top end of the longitudinal bar for attaching the top end of the bar to a tensioning arm  41 . A compression spring  4   s  has first  6   b  and second  6   t  ends, and is located around a portion  102   a  of the longitudinal bar  102 . A first spring retainer  4   b  engages with and retains the first end  6   b  of the spring  4   s.  A first locking nut  5   a  fits to the threaded portion  102   a  of the bar  102  and retains the first spring retainer  4   b  longitudinally in place relative to the bar  102 . The longitudinal bar  102  is rotationally freely coupled to the attachment device  103  to permit free axial rotation of the bar about the longitudinal axis  102   x  relative to the attachment device  103 . An engagement head  102   h,    302   h  is attached to and located at or proximate the bottom end  102   b  of the longitudinal bar  102  for engagement with a tool. 
     Clearly the skilled person will recognize that various aspects, embodiments and elements of the present application, including as illustrated in the figures, may be arranged in differing combinations, any and all of which may be considered to fall within the ambit of the inventive concept. The invention will be defined by the following claims.