Abstract:
A tension adjusting device is attached to an axle member of a driven wheel of a vehicle and is coupled to a forked frame member to adjust tension of a chain. The tension adjusting device has two tension adjusters joined to each side of the axle member that engages a guide recess of the forks of the frame member and support the axle fastener to secure the axle member to the two adjustment plates. The two adjustment plates include extending members that each extend over an end of each fork. An adjustment bore is drilled through the extending member and aligned with the ends of the forks. An adjustment stud is affixed through the adjustment bores to make contact with the end of the forks and to allow the axle member of the driven wheel to move in an adjustment slot to adjust the tension of the chain.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to wheeled vehicles with a flexible power transmission mechanism such as a chain or belt. More particularly, this invention relates to devices for the adjustment of tension in a flexible power transmission mechanism. 
   2. Description of Related Art 
   Wheeled vehicles such as motorcycles generally have a drive sprocket or pulley attached to the drive shaft of the motor. The drive sprocket or pulley is then coupled to a flexible power transmission mechanism. In the case of the drive sprocket, the flexible power transmission mechanism is a chain. 
   Alternately, in the case of the drive pulley, the flexible power transmission mechanism is a belt. The chain or belt is then coupled to a sprocket or pulley affixed to driven wheel. The driven wheel is mounted to an axle that is secured to the frame of the motorcycle. Generally the frame of the motorcycle has a forked swing arm. The axle is secured to the swing arm. The swing arm allows vertical movement of the driven wheel. This vertical movement is dampened by a shock absorbing system connecting the swing arm and a rigid portion of the frame. 
   As is known in the art, the chain or belt must have correct tension to efficiently transfer power from the motor to the driven wheel. Motorcycles such as those manufactured by Yamaha Motor Corporation, USA, Kawasaki Motors Corp. U.S.A., American Suzuki Motor Corporation, Ducati Motor Holding S.p.A., and other motor cycle manufacturers integrate a chain tensioner or puller with the driven wheel of their motor cycles. The chain tensioner is coupled to the forks of the swing arm and is placed in a recessed axle slot of the forks. The chain tensioner is attached to the axle of the driven wheel. 
   In many of the current models of motorcycle, the chain tensioner is placed forward of the driven axle. The chain tensioner pushes the axle within an axle bore that is opened within the recessed guide of the forks. The chain tensioner is often adjusted by rotating a threaded stud captivated in a housing placed in the recess guide and secured to the forks. The threaded stud generally has a hexagonal head that is adjusted with a standard wrench. For motorcycles involved in “off-road” touring or racing, the chain tensioner often becomes fouled with mud and debris. This makes the adjustment difficult. Further, the size of the hexagonal head of the threaded stud is normally small and it is difficult to perform the adjustment during a race or in an “off-road” environment. 
   U.S. Pat. No. 6,450,282 (Gogo, et al.) describes a swing-arm support structure for a motorcycle. The swing-arm illustrated shows a slide adjuster mechanism for adjusting the tension of a chain of a motorcycle. 
   U.S. Pat. No. 5,524,725 (Schantzen) illustrates a chain drive that has an automatic chain tension adjustor. 
   U.S. Pat. No. 5,337,849 (Eavenson Sr., et al.) details a mechanism for mounting an axle to a vehicle. An adjustable tensioning mechanism includes a bolt and nut for shifting the second axle housing with respect to the first axle housing to thereby adjust the tension in the chain. 
   U.S. Pat. No. 5,049,114 (Hayden) describes a self-adjusting chain tensioning device made up of a spring loaded rubbing block that is in continuous contact with the chain. 
   U.S. Pat. No. 4,616,729 (Kasai) details a transmission chain adjuster for motorcycles. An arrangement is provided for adjusting the tension in each of two chains and one of these adjusting mechanisms moves the pivot point of the trailing arm relative to the frame. 
   U.S. Pat. No. 4,237,744 (Jolly) describes a chain tension adjusting device using a cam mounted within a sleeve that moves a driven wheel axle on a fork frame. 
   U.S. Pat. No. 4,061,050 (Bolger) illustrates a compensating mechanism to provide constant tension between a driving sprocket and a driven sprocket of a motorcycle. 
   U.S. Pat. No. 5,240,087 (Parker) describes a one-sided rear swing arm suspension system for a motorcycle with a chain-driven rear wheel. The tension of the drive chain may be adjusted without affecting the ride height of the motorcycle by an adjustment yoke that moves the axle longitudinally on the swing arm by means of an adjustment stud extending from the swing arm, and a corresponding adjustment nut entrapped in the neck of the yoke. 
   U.S. Pat. No. 5,964,312 (Maldonado) has a combination suspension swing arm and light assembly also serving to cover the axle nuts and axle adjustment screws for a motorcycle. The lenses are removable to expose both axle nuts and axle adjustment screws, permitting the full adjustment of both. 
   SUMMARY OF THE INVENTION 
   An object of this invention is to provide a tension adjusting device that adjusts the tension of a flexible power transmission mechanism for wheeled vehicles such as motorcycles. 
   Another object of this invention is to provide a tension adjusting device that replaces the original equipment tension adjusting device that has been attached to an axle member of a driven wheel of a vehicle and coupled to a forked frame member to adjust tension of a flexible power transmission mechanism that transfers power from a drive shaft of the wheeled vehicle to the driven wheel. 
   To accomplish at least one of these objects, a tension adjusting device has a first tension adjuster joined to a first side of the axle member and a second tension adjuster joined to a second side of the axle member. The first tension adjuster includes a first adjustment plate. The first adjustment plate has a first dimension to slidably engage a guide recess of a first fork of the forked frame member and a second dimension sufficient to support a first axle fastener to the axle member to the first adjustment plate. The first adjustment plate further includes an extending member that extends over an end of the first fork. An axle bore is drilled through the first adjustment plate such that the first side of the axle member may pass through the first adjustment plate. The first side of the axle member receives the first axle fastener to secure the axle member to the first adjustment plate and couple the first adjustment plate to the first fork of the forked frame member. A capturing recess is let into the first adjustment plate to secure the first axle fastener to prevent movement of the first axle fastener during the coupling of the driven wheel. The first adjustment plate has an adjustment bore drilled through the extending member and aligned with the end of the first fork. A first adjustment stud is affixed through the adjustment bore to the first adjustment plate such that the adjustment stud is in contact with the end of the first fork to allow the axle member of the driven wheel to move in an adjustment slot within the guide recess to adjust the tension of the power transmission mechanism. 
   The second tension adjuster has a second adjustment plate with a first dimension to slidably engage a guide recess of a second fork of the forked frame member and a second dimension sufficient to support a second axle fastener to the axle member to the second adjustment plate. The second adjustment plate further includes an extending member that extends over an end of the second fork. An axle bore is drilled through the second adjustment plate such that the second side of the axle member may pass through the second adjustment plate. The second side of the axle member receives the second axle fastener to secure the axle member to the second adjustment plate and couple the second adjustment plate to the second fork of the forked frame member. The second adjustment plate has an adjustment bore drilled through the extending member and aligned with the end of the second fork. A second adjustment stud is affixed through the adjustment bore to the second adjustment plate such that the adjustment stud is in contact with the end of the second fork to allow the axle member of the driven wheel to move in an adjustment slot within the guide recess to adjust the tension of the power transmission mechanism. 
   The adjustment bores of the first and second adjustment plates may be threaded. Alternately, each adjustment bore may have a captivating nut secured to the first and second adjustment plates within the adjustment bores to accept the first adjustment stud. The first and second adjustment studs may be threaded and each includes a securing nut. The securing nut locks the first and second adjustment studs respectively to the first and second adjustment plates, when the first and second adjusting studs have moved the driven wheel such that the flexible power transmission mechanism has the final tension. 
   The first and second adjustment plates each include at least one guide marking placed to insure that the axle member is oriented with respect to the forked frame member. In tensioning the flexible power transmission mechanism, one of the adjustment studs is rotated to move the axle member within the adjustment slot of the forks of the forked frame member. When the flexible power transmission mechanism is at the final tension, the location of the guide marking is noted and the other adjusting stud is rotated to move the axle member to align with guide marking. 
   In the preferred embodiment of this invention, the flexible power transmission mechanism is a chain and the chain is engaged with teeth of a sprocket coupled to the driven wheel. However, in an alternate embodiment of this invention, the flexible power transmission mechanism is a belt and the belt is placed on a pulley coupled to the driven wheel. 
   The first and second adjustment plates are formed of an aircraft grade aluminum. Conversely the materials for the first and second adjustment plates may be steel, titanium, or carbon epoxy. 
   An original equipment tension adjusting device is replaced by removing the original equipment tension adjusting device from the forked frame member and the axle member. The replacement tension adjusting device is installed on axle member. The driven wheel with the replacement tension adjusting device is placed between the first and second fork of the forked frame member. The flexible power transmission mechanism is coupled to the driven wheel. The placement of the driven wheel is modified such that the extending members of the first and second adjustment plates are aligned respectively with the ends of first and second ends of the forked frame member and the flexible power transmission mechanism has a preliminary tension. The first and second adjustment studs are varied to move the driven wheel incrementally to adjust the flexible power transmission mechanism to the final tension. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a – 1   c  are respectively the front, top and side plan views of the first tension adjuster of the tension adjusting device of this invention. 
       FIGS. 2   a – 2   d  are respectively front, top and two side plan views of second tension adjuster of the tension adjusting device of this invention. 
       FIGS. 3   a – 3   b  are respectively front and top plan views of the first tension adjuster of the tension adjusting device of this invention illustrating multiple guide marks. 
       FIG. 4  is a partial top view of a motorcycle illustrating a swing arm with the driven wheel showing the placement of the tension adjusting device of this invention. 
       FIG. 5  is a partial side view of a motorcycle illustrating a swing arm with the driven wheel showing the placement of the tension adjusting device of this invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   To make the adjustment of the chain tension of a motorcycle easier than is provided by chain tensioners currently employed, the chain tensioning device of this invention replaces the original equipment chain tensioners. The chain tension device of this invention has two chain tension adjusters that are joined to the axle of the driven wheel of the motorcycle and coupled to it through an adjustment slot within a recessed guide of the forks of the swing arm frame member of the motorcycle. The tension adjusting device permits the adjustment of the chain tension with standard wrenches or sockets and allows for more rapid changes of sprocket gearing. Further, the tension adjusting device pulls the axle rather than pushing the axle as in standard chain tensioners in current usage. Additionally, the tension adjusting device of this invention permits replacement of the chain tensioner in current usage that has stripped threads in the swing arm frame member to which the chain tensioner is secured. The tension adjusting device of this invention is not secured to the swing arm frame member by the threaded bore thus making rethreading of stripped threads unnecessary. 
   Refer now to  FIGS. 1   a – 1   c  for a detailed description of the first chain tensioner of the chain tension adjusting device of this invention. The first chain tensioner has an adjustment plate  5  with an extending member  10  formed at right angles to the adjustment plate  5 . The length L 1  of the adjustment plate is sufficient to fit in the recessed guide of one fork of the swing arm frame member of the motorcycle and thus permits the extending member  10  to over lap the end of the one fork of the swing arm frame member. In the preferred embodiment, the length L 1  of the adjustment plate  5  is approximately 3.000″. 
   The width W 1  of the adjustment plate  5  is sufficiently wide so that the adjustment plate  5  firmly fits the width of the recessed guide of the one fork. In the preferred embodiment the width W 1  is from approximately 1.50″ to approximately 1.60″. The extending member  10  has a sufficient height T 2  to allow the extending member  10  to overlap the width of the one fork of the sing arm frame member. In the preferred embodiment, the height T 2  is from approximately 1.050″ to approximately 1.125″. 
   The axle of the driven wheel of the motorcycle is normally smooth for most of its length with only a small threaded region to accept an axle nut for securing the driven wheel to the swing arm frame member. The thickness T 1  of the adjustment plate  5  is designed to be adequately thick to prevent the axle nut from being turned to the bottom of the threaded region. Further, the thickness T 1  is designed to allow the axle nut to just cover the threaded region of the axle and not leave any of the threads of the threaded region of the axle extended beyond the axle nut. This prevents mud and debris from accumulating in the threaded region. In the preferred embodiment, the thickness T 1  is approximately 0.50″. 
   An axle bore  15  is drilled into the adjustment plate  5 . The axle bore  15  is centered on the width dimension W 1  of the adjustment plate  5  and is placed at a distance from a leading edge  50  of the adjustment plate  5  such that the axle of the driven wheel is essentially centered within the recessed guide of the one fork of the swing arm frame member while the leading edge is in contact with a forward edge of the recessed guide. The diameter d 1  of the axle bore is sufficiently large to accommodate the diameter of the axle. In the preferred embodiment the diameter d 1  of the axle bore  15  is from approximately 0.875″ to approximately 1.070″. 
   A capturing recess  20  is let into the adjustment plate  5  and is centered on the width dimension W 1  of the adjustment plate  5 . The width W 2  of the capturing recess is determined by the size of the axle nut. In the preferred embodiment the capturing recess has a width of approximately 1.3″. The Capturing recess  20  is used to hold the axle nut threaded on one end of the axle from turning when a second axle nut is threaded on a second end of the axle. The length L 2  of the capturing recess is set to allow the axle nut to fit within the capturing recess. In the preferred embodiment, the length L 2  is approximately 1.750″. The depth T 3  of the capturing recess  20  is sufficient to hold the one axle nut, but not too deep to have an impact on the strength of the adjustment plate  5 . In the preferred embodiment of the capturing recess  20 , the depth T 3  is approximately 0.175″. 
   An adjustment bore  30  is drilled in the extended member to accept an adjustment stud  25 . The adjustment stud  25  is centered on the width dimension W 1  of the adjustment plate  5  and essentially centered in the height dimension of the extended member. This location must be set such that the adjustment stud  25  can contact the end of the fork of the swing arm frame member. The adjustment bore  30  has a diameter that can accommodate a captivated nut  35 . Alternately, if the adjustment bore is to be threaded, the adjustment bore  30  must be the diameter of the adjustment stud  25 . In the preferred embodiment, the adjustment stud is approximately 8 mm in diameter. If the captivated nut  35  is employed, the adjustment bore is approximately 0.50″ in diameter or of a sufficient diameter to permit a press fit of the captivated nut  35 . 
   A securing lock nut  40  is threaded on to the adjustment stud  25 . When the driven wheel is coupled to the forks of the swing arm frame member, the securing lock nut  40  is unthreaded on the adjustment stud  25 . The driven wheel is placed between the forks of the swing arm frame member and set to tension the chain to a preliminary tension. The axle nuts are tightened to hold the placement of the driven wheel. The adjustment stud  25  is then adjusted to move the driven wheel to adjust the chain to a final level. The securing lock nut  40  is threaded to impinge upon the extending member  10  of the adjustment plate  5  and lock the adjustment stud  25  in place. 
   The guide marks  45  are placed on the top and bottom surfaces of the adjustment plate  5  and are aligned with the center of the axle bore  15 . The fork of the swing arm frame member will have multiple marks or a similar calibration marking to allow of the axle of the driven wheel to be correctly aligned during the movement to tension the chain. The guide marks  45  are shown at the top and bottom of the adjustment plate  5  but may also be on the front face of the adjustment plate  5 . 
     FIGS. 2   a – 2   d  provide a detailed description of the second chain tensioner of the chain tension adjusting device of this invention. The second chain tensioner has an adjustment plate  105  with an extending member  110  formed at right angles to the adjustment plate  105 . The length L 1  of the adjustment plate is sufficient to fit in the recessed guide of one fork of the swing arm frame member of the motorcycle and permits the extending member  110  to over lap the end of the one fork of the swing arm frame member. In the preferred embodiment, the length L 1  of the adjustment plate  105  is approximately 3.125″. 
   The width W 1  of the adjustment plate  105  is sufficiently wide to allow for the adjustment plate  105  to firmly fit the width of the recessed guide of the one fork. In the preferred embodiment, the width W 1  is from approximately 1.50″ to approximately 1.60″. The extending member  110  has a height T 2  that is sufficient to allow the extending member  110  to overlap the width of the one fork of the swing arm frame member. In the preferred embodiment, the height T 2  is from approximately 1.050″ to approximately 1.125″. 
   The axle of the driven wheel of the motorcycle is normally smooth for most of its length with only a small threaded region to accept an axle nut for securing the driven wheel to the swing arm frame member. The thickness T 1  of the adjustment plate  105  is designed to be adequately thick to prevent the axle nut from being turned to the bottom of the threaded region. Further, the thickness T 1  is designed to allow the axle nut to just cover the threaded region of the axle and not leave any of the threads of the threaded region of the axle extended beyond the axle nut. This prevents mud and debris from accumulating in the threaded region. In the preferred embodiment, the thickness T 1  is approximately 0.50″. 
   An axle bore  115  is drilled into the adjustment plate  105 . The axle bore  115  is centered on the width dimension W 1  of the adjustment plate  105  and is placed at a distance from a leading edge  150  of the adjustment plate  105  such that the axle of the driven wheel is essentially centered within the recessed guide of the one fork of the swing arm frame member while the leading edge is in contact with a forward edge of the recessed guide. The diameter d 1  of the axle bore is sufficiently large to accommodate the diameter of the axle. In the preferred embodiment, the diameter d 2  of the axle bore  115  is from approximately 0.875″ to approximately 1.070″. 
   There is no capturing recess let in the into the adjustment plate  105 . The axle nut  315  is free to be rotated with a wrench in order to tighten the axle  325  to the swing arm frame member  300  of the motorcycle. 
   An adjustment bore  130  is drilled in the extended member to accept an adjustment stud  125 . The adjustment stud is centered on the width dimension W 1  of the adjustment plate  105  and essentially centered in the height dimension of the extended member. This location must be set such that the adjustment stud  125  can contact the end of the fork of the swing arm frame member. The adjustment bore  130  has a diameter that can accommodate a captivated nut  135 . Alternately, if the adjustment bore is to be threaded, the adjustment bore  130  must be the diameter of the adjustment stud  125 . In the preferred embodiment, the adjustment stud  125  is approximately 8mm in diameter. If the captivated nut  135  is employed, the adjustment bore is approximately 0.50″ in diameter or of a sufficient diameter to permit a press fit of the captivated nut  135 . 
   A securing lock nut  140  is threaded on to the adjustment stud  125 . When the driven wheel is coupled to the forks of the swing arm frame member, the securing lock nut  140  is unthreaded on the adjustment stud  125 . When the driven wheel is placed between the forks of the swing arm frame member and set to tension the chain to a preliminary tension, the axle nuts are tightened to hold the placement of the driven wheel. The adjustment stud  125  is then adjusted to align axle the driven wheel within the swing arm frame member. The securing lock nut  140  is threaded to impinge upon the extending member  110  of the adjustment plate  105  and lock the adjustment stud  125  in place. 
   The guide marks  145  are placed on the top and bottom surfaces of the adjustment plate  105  and are aligned with the center of the axle bore  115 . The fork of the swing arm frame member will have multiple marks or a similar calibration mark to allow the axle of the driven wheel to be correctly aligned during the movement to tension the chain. The guide marks  145  are shown at the top and bottom of the adjustment plate  105  but may also be on the front face of the adjustment plate  105 . 
   The guide marks  45  ( FIGS. 1   a – 1   c ) and  145  ( FIGS. 2   a – 2   d ) are shown as single guide marks with multiple calibration marks being present on the fork of the swing arm frame member.  FIGS. 3   a  and  3   b  illustrate the first chain tensioner of  FIGS. 1   a – 1   c  with multiple guide marks  245 . In this instance, the forks of the swing arm frame member have single calibration reference marks for assisting in the aligning of the axle within the swing arm frame member. 
   Refer now to  FIGS. 4 and 5  for a discussion of the placement, installation, and operation of the chain tension adjusting device of this invention. As described above, a motorcycle has a drive sprocket  375  attached to the drive shaft  380  of the motor  385 . The drive sprocket is then coupled to a flexible chain  365  that acts as a flexible transmission mechanism. The driven wheel  305  has an axle  325  that is placed between the forks  302  and  304  of the swing arm frame member  300  of the motorcycle. The chain  365  is placed on a sprocket  360 . The ends of the wheel hub  310  are placed in an axle slot of  345  in each fork  302  and  304  of the swing arm frame member  300 . The first chain tensioner  330  is placed on the end of the wheel hub  310  and in the guide recess  340  of one fork  304  of the swing arm frame member  300 . Similarly the second chain tensioner  320  is placed on the end of the wheel hub  310  and in the guide recess of the second fork  302  of the swing arm frame member. The driven wheel  305  is moved until the chain has a preliminary tension. The first adjustment plate  5  is moved within the guide recess  340  until the extending member is aligned with the end of the fork  304 . The adjustment securing nut  40  is rotated to allow the first adjustment stud  25  to be rotated such that it is in contact with the end of the fork  304 . Similarly, the second adjustment plate  105  is moved within the guide recess (equivalent to the guide recess  340  of fork  304 ) until the extending member is aligned with the end of the fork  302 . The adjustment securing nut  140  is rotated to allow the first adjustment stud  125  to be rotated such that it is in contact with the end of the fork  302 . 
   The axle  325  is secured within the capturing recess  20  ( FIGS. 1   a – 1   c ) and the axle nut  315  is tightened to secure the driven wheel  305  between the forks  302  and  304  of the swing arm frame member  300 . The adjustment stud  25  is then rotated to pull the wheel hub  310  and thus increase tension on the chain  365  until a final tension is achieved. The placement of the guide mark  45  relative to a calibration reference mark  355  on the fork  304  is noted. The adjustment stud  125  is then rotated to pull the end of the wheel hub  310  until the reference mark  145  is aligned with the calibration reference mark  355  of the fork  302 . The securing nuts  40  and  140  are rotated until they have respectively impinged upon the extending members  10  and  110  thus securing the adjustment studs  25  and  125  from movement during operation of the motorcycle. 
   The first and second adjustment plates  5  and  105 , in the preferred embodiment, are formed of an aircraft grade aluminum. Conversely, the materials for the first and second adjustment plates  5  and  105  may be steel, titanium, carbon epoxy or other suitable material that can withstand the conditions of operation at the axle  325  of a motorcycle and the tension of the chain  365 . 
   In the preferred embodiment of this invention as described, the flexible power transmission mechanism is a chain  365 . The chain  365  is engaged with the teeth of a sprocket  360  coupled to the driven wheel  305 . However, in an alternate embodiment of this invention, the flexible power transmission mechanism is a belt and the belt is placed on a pulley coupled to the driven wheel. 
   While this invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.