Abstract:
A specially configured wrench is fitted to the fork structure of the rear wheel of a motorcycle to transmit rotational torque to the axle and move the rear wheel axle and sprocket to adjust and accurately set the tension in the drive belt of the motorcycle to a desired level. Further, a method is disclosed for reducing slack, changing, and/or setting a desired tension in the flexible power transmission mechanism of a motorcycle, the mechanism exemplified by a chain or drive belt having upper and lower reaches wrapped about respective of a rotatable forward motor drive sprocket and a rotatable rear wheel drive sprocket and used in cooperation with a fork structure for mounting the rear wheel and a cam-operated structure for repositioning the rear sprocket and associated axle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 12/012,250, filed Feb. 1, 2008, now abandoned which claims the benefit of provisional Application No. 60/899,188, filed Feb. 2, 2007, the entire disclosure of which is incorporated herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to motorcycles with a flexible power transmission mechanism, such as a chain or drive belt, and having cam operated structure for changing the tension in such mechanism, and more particularly, this invention relates to an apparatus and method for use in adjusting the cam operated mechanism to accurately set the tension in the drive belt of the motorcycle having such mechanism. 
     2. Description of the Prior 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. Alternatively, in the case of the drive pulley, the flexible power transmission mechanism is a belt. 
     The chain or belt is coupled to a sprocket or pulley affixed to a 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 and the axle is secured to the swing arm. The swing arm allows bounce, or 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. Accordingly, chain or belt-tensioning devices have been proposed. Such devices are used to adjust for the natural stretch of the chain. When power is provided or eliminated to the drive sprocket, die chain may be taut on the top or bottom. Particularly in motorcycle chain drives, vibration occurs in normal operation, resulting in a loss of power transfer. 
     Some motorcycle manufacturers, such as those manufactured by Yamaha Motor Corporation, USA, Kawasaki Motors Corp., USA, American Suzuki Motor Corporation, Ducati Motor Holding S. p. A., integrate a chain tensioner or puller with the driven wheel of their motorcycles. 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 another known tension adjusting device, two tension adjusters are provided and joined to each side of the axle member that engages a guide recess of the forks of the frame member. A threaded adjustment stud in each tension adjuster contacts a respective fork to move the axle member in an adjustment slot to adjust the tension of the chain. In operation, separately adjusting the two studs independently of one another may result in the opposite sides of the shaft being pulled differently and the tension in the chain being other than expected. 
     In many of the current models of motorcycle, such as those manufactured by Harley-Davidson, a chain or belt tensioner includes two cams, and two guide plates, the cams being joined to the opposite ends of the driven shaft, and the guide plates being joined to the opposite sides of the motorcycle frame and forward of the driven axle. The belt tension is adjusted by rotating a first hex head fixedly joined to one cam, wherein both cams are simultaneously rotated and their respective cam surfaces progressively engaged with their respective guide plates. This rotation pushes the driven axle within an axle bore that is opened within the recessed guide of the forks. Thereafter, a second hex head on the other end of the drive shaft is threadably advanced towards the frame and to drive the cams into gripping engagement with the forks. 
     However, in operation, the mechanic must hold the first hex head stationary, while rotating the second hex head. As a result, torque placed on the driven shaft by the second hex head being secured thereto may cause the first head to rotate by a small amount. This will result in a back off (i.e., move the shaft back), thus changing the desired tension that was set. 
     It is to be appreciated that there is a need for a tensioning arrangement that ensures that the tension that is set in the belt during tensioning remains the tension in the belt following tensioning. 
     SUMMARY OF THE INVENTION 
     An object of this invention is the provision of a tension-adjusting device that adjusts the tension of a flexible power transmission mechanism for conventional wheeled vehicles such as a motorcycle. 
     Another object is the provision of a method by which an after market purchaser may adjust the tension of a motorcycle drive belt of a conventional motorcycle using a simple tension adjustment socket wrench according to this invention. 
     Another object of the invention is to provide a novel adjusting device in the nature of a socket wrench which is of simple construction, inexpensive, can be easily manufactured, and rapidly used as an aid in the adjusting the belt tension of a motorcycle drive system. 
     Another object of this invention is the provision of a socket wrench for positioning and immobilization of an eccentric camshaft and thereby set the tension in the drive belt operably connected to the camshaft. 
     Another object of the invention is the provision of a torque transmitting wrench for use with standard elements of a conventional motorcycle and in setting the belt tension thereof, the wrench including a lever connectible to the axle that supports the rear wheel of the motorcycle, the axle operably connected to the drive belt via a rear sprocket, and an actuator rod atop a motorcycle bracket, the rod vertically positionable relative thereto wherein to rotate the lever, move the driven shaft rearwardly and increase the belt tension and immobilize the shaft, and then securing the drive belt in place, whereupon the wrench is removed and the belt tension achieved. 
     Another object of this invention is to provide a tension adjusting device that is used in combination with and attached to the axle member of the driven wheel of a motorcycle and coupled to a frame member associated with the drive wheel whereby to adjust tension of a flexible power transmission mechanism that transfers power from the drive shaft to the driven shaft of the motorcycle 
     To accomplish at least one of these objects, there is provided a wrench for setting the tension for a drive belt of a motorcycle, the drive belt mounted to a frame of the motorcycle by a drive shaft and a driven shaft, the wrench comprising: 
     an elongated lever having first and second end portions at right angles to one another, the first end portion including means for engaging and rotating one end of the driven shaft, the second end portion including a flange, and 
     an actuator connected to the flange for movement transverse thereto, the actuator having a distal end portion for engaging the frame wherein relative movement between the actuator and flange member causes the lever to rotate and the driven shaft to rotate from a first position into a second position wherein the shaft is immobilized by the wrench and the drive belt is in a desired tension. 
     In a preferred embodiment, the driven shaft is provided with a hex shaped nut, and the means for engaging and rotating is in the form of a generally circular opening the wall of which has gripping surfaces to engage the nut. 
     In accomplishment of another object, there is provided a motorcycle belt torque transmitting wrench of the type having an elongated lever including first and second end portions disposed at a right angle to one another, the right angle between the first and second end portions being offset along an offset included angle θ, θ being less than 90 degrees, the first end portion having an opening configured to receive a first nut, and the second end portion including a flange, wherein the improvement comprises: 
     the opening having a closed end and being generally circular in shape, the opening further having at least six gripping surfaces to engage the first nut; 
     a threaded actuator threadably connected to the flange for movement transverse thereto, the threaded actuator having a non-abrasive foot secured to a distal end portion of the threaded actuator for engaging a surface, and a proximal end portion of the threaded actuator having a second nut fixedly secured thereto; and 
     the flange having a threaded hole configured to receive the threaded actuator, wherein rotational movement of the actuator rotates the wrench about the first nut. 
     In accomplishment of another object, there is provided a method of adjusting and setting a desired tension in a drive belt of a motorcycle of the type including a frame having a first and second forks and associated guide brackets, a driven shaft having first and second ends, respectively, connected to the first and second forks, each end of the shaft having an eccentric cam that engages a respective guide bracket upon rotation of the driven shaft, the first cam having an engagement nut fixed thereto and the second cam being connected to the second end of the shaft by a second engagement nut, and a drive belt operably associated, in part, in driving relation with the driven shaft, the steps of the method comprising: 
     providing a socket wrench, the socket wrench including an elongated lever having first and second end portions, the end portions being at right angles to one another with the first end portion including a socket for engaging and rotating the first engagement nut and the second end portion including an actuator connected for movement relative to the lever, the actuator having an upper end portion and a lower end portion, the lower end portion for engaging the first guide bracket wherein relative movement between the actuator and lever causes the lever to rotate about the first and second engagement nuts, 
     positioning the socket about the first engagement nut and the lower end portion of the actuator atop the first guide bracket, 
     rotating the threaded actuator such that the lever, the first engagement nut, and the driven shaft rotate in a direction causing both cams to rotate and engage their respective guide brackets and push the driven shaft away from the guide brackets and into a position wherein the drive belt has a desired tension, 
     tightening the second engagement nut about the second end of the driven shaft such that the second engagement nut presses the second cam towards and against the second fork, with progressive tightening causing both of the cams to be clamped against their respective forks and the driven shaft to be locked in the position wherein the drive belt has the tension maintained, whereupon the wrench is removed. 
     Desirably, in effecting the tensioning herein, the tension adjusting device, or wrench, may be used in a confined area with limited turning space. Preferably, the central socket is 12-point (double-hexagonal) configuration, in part because the 12-point socket doubles the number of starting positions. However, the socket could be at least 6-point (hexagonal), or of other configuration other than hexagonal, depending on the nut used on the motorcycle. 
     The actuator desirably extends through a complementary threaded hole in the second end portion of the socket wrench, the upper end portion of the actuator having a hexagonal drive nut fixedly attached thereto and a foot fixedly attached to the lower end portion of the actuator. 
     In addition, the first engagement nut is preferably hexagonal in shape, and the socket is hexagonal in shape and dimensioned for close fitment about the engagement nut. 
     In yet another embodiment according to this invention, there is provided a wrench for tensioning a drive belt of a motorcycle of the type including a support frame having a motor and a fork assembly for mounting a rear wheel, a drive shaft, connected to the motor, and a driven shaft having first and second ends connected to opposite sides of the fork assembly, the first and second ends each including, respectively, a cam and a hexagonal shaped head, the fork assembly having first and second guide members, the drive belt associated in operable driving relation with the shafts, and rotation of the first hex head causes the cam to engage the first cam guide and push, the shaft away therefrom, comprising: 
     an elongated lever having a shaped opening therethrough, the opening formed by a succession of gripping surfaces that are complementary to the hexagonal shaped heads and adapted to allow passage of the first hex head therethrough in a manner that die gripping surfaces are juxtaposed in close gripping relation with, corresponding sidewalls of the hex head, and 
     an elongated actuator rod having lower, upper and medial portions, the medial portion threadably connected to the lever, the lower portion adapted to engage the first guide member, and the upper portion positioned for rotational engagement, such that, relative rotation between the lever and actuator rod causes the lever to rotate the cam against the first guide member and push the driven shaft away from the guide and increase the tension in the drive belt, the lever and rod operating to immobilize the driven shaft in the position for tightening the hex heads into clamped relation with the fork assembly. 
     The present invention will be more clearly understood with reference to the accompanying drawings and to the following Detailed Description, in which like reference numerals refer to like parts and where: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the rear drive wheel section of a conventional prior art motorcycle including a flexible power transmission drive belt or chain extending between the rear wheel and the drive motor; 
         FIG. 2  is a simplified exploded perspective view of the rear drive wheel section of  FIG. 1  with portions removed to illustrate elements for tensioning the drive belt; 
         FIG. 3  is a side view of a socket wrench according to this invention for use in ensuring that a desired tension is set and maintained when adjusting the tension in the drive belt of the rear wheel section in the motorcycle shown in  FIG. 1 , the socket wrench including a lever bracket with a socket and a vertically adjustable actuator rod to apply rotational torque to the lever bracket; 
         FIGS. 4 and 5  are perspective views of the lever bracket shown in  FIG. 3  without the actuator rod; and 
         FIGS. 6 and 7  are partial side elevation views showing the method of tensioning the drive belt in the motorcycle of  FIG. 1  using the socket wrench according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning now to the drawings,  FIG. 1  illustrates part of a conventional prior art motorcycle  10  that includes a frame  12  and an engine/transmission assembly  14  connected to the frame  12 . The engine/transmission assembly  14  includes an engine and a transmission connected to the engine. The engine and the transmission of the engine/transmission assembly  14  could either include a single integral housing or separate housings connected together. The transmission includes an output or drive shaft  16  that is rotated in response to operation of the engine. While not shown, the motorcycle  10  also includes a steering assembly and a front wheel rotatably mounted to the steering assembly. 
     A rear frame or swing frame member  18  is pivotably mounted to the frame  12  and includes a wheel mounting fork structure formed by a pair of brackets or fork members  20  and  22  that are axially extending, laterally spaced, and form a U-shaped recess for mounting the rear wheel  24  of the motorcycle therebetween. A rear axle or wheel shaft  26  extends between the fork members or brackets  20  and  22  to mount the wheel  24  in the recess and connect the axle to the forks. Each fork  20  and  22  has a horizontally extending guide slot  36  to receive an opposite respective end portion  26   a  and  26   b  of the axle or wheel shaft  26 . A flexible power transmission dive chain or belt  28  having an upper and lower reach is wrapped about a rotatable motor drive sprocket  30 , attached to the drive shaft  16  of the motor, and a rotatable rear wheel or driven sprocket  32 . 
     A chain or belt tensioning arrangement to control and/or adjust the slack and/or tension in the upper and lower reaches of the drive chain or belt is provided. The tensioning arrangement includes the distal end of each fork  20  and  22  including a cam receiver or cam guide  38  and a cam  40 . The cam guide  38  includes a vertical end face  42 , spaced forwardly and away from the axle guide slot  36  in the respective fork. The fork members  20  and  22  include a horizontal support or reference surface  44 . A cam  40  is joined to each respective end  26   a  and  26   b  of the axle or shaft  26 , the cams being like shaped. Each cam includes a peripheral surface  46 , in the form of a spiral, that is adapted to engage the end face  42 . The peripheral surface  46  is eccentric to the geometric center axis of shaft  26 . When joined to their respective shaft ends, the cams and their respective eccentric peripheral surfaces  46  are symmetrically disposed, mirror images of one another, and adapted to be simultaneously rotated by the axle  26 , resulting in the axle axis and both ends  26   a  and  26   b  of the axle  26  moving towards or away from the ends face in like amount, depending on the direction of rotation of the wheel axle or shaft  26 . 
     While the method of assembly may differ, in the method as shown in  FIG. 2 , the cam  40  associated with the shaft end  26   a  is fixedly joined thereto, and a hexagonal nut  48  fixedly secured to the shaft end  26   a  and against the exterior cam surface  50  (i.e., facing away from the fork member). The interior face of the cam  40  is adapted to be driven against the fork member  26   a  associated therewith. The other shaft end  26   b  is provided with thread  52  for threadable connection with a securement member in the form of a hexagonal nut  54 . 
     The cam associated with the shaft end  26   b  includes a through passage  56  of square shape that mates with a complementary cross-section  58  on the end portion  26   b  of the axle  26 . This passage  56  operates to prevent rotation of the cam relative to the axle, properly orient the two cams with one another when mounted to the axle  26 , and ensure that the two cams will rotate simultaneously with rotation of the driven shaft or axle  26 . Threadable connection of the nut  54  to the thread  52  of the axle or shaft  26  operates to drive the cam towards the fork  22 . Continued rotation and advancement of the securement hex head nut  54  causes the two cams to clampingly press against their respective forks  20  and  22 . The cams, connected to the axle end portions, rotate and drive the shaft and rear sprocket rearward, set a tension and/or removes slack from the drive chain, and is locked in place in relation with the rear swing frame  18 . 
     In setting the tension, the nut  54  is loosened and the nut  48  is rotated, causing both cams to rotate, whereupon the outer surfaces  46  press against the cam receivers or end faces  42 . This cam action forces the axle  26  to move within the guide slot  36  along the horizontal plane “S” in a direction away from the end face  42 , and from a first to a second position, thereby reducing the slack and increasing the tension in the reaches of the flexible drive belt. At this point, the nut  54  is torqued about the shaft end  26   b . This torque may have a tendency to rotate the axle  26  and cause the cam at the other shaft end  26   a  to rotate and the desired tension lessened, or changed from that which was expected. 
     According to this invention, there is provided a socket wrench or tensioning tool, generally indicated by the number  60 , for obviating the problem in tension change (e.g., decrease) during final tightening. As shown in  FIGS. 3-5 , the tool  60  comprises an elongated lever  62  formed from a generally planar rectangular sheet of steel to include a first end or plate portion  68  and a second end or plate portion  70  at a right angle to the plate portion  68 . The right angle bend is oriented at an offset included angle θ, such as shown in  FIGS. 3 and 5 . The lever  62  has a shaped socket or opening  64  passing through the plate portion  68  thereof and a threaded bore  74  in the plate portion  70  thereof for receiving an externally threaded actuator rod  66 . The axis of the threaded actuator rod  66  is offset from the opening  64  so that rotational movement of the actuator rod  66  effectuates rotational movement about the hex head  48 , as discussed below. Therefore, the offset included angle  8  is less than ninety degrees (90°). 
     The socket or opening  64  is formed by a succession of V-shaped gripping surfaces  72  that are complementary to the hexagonal shape of the nuts or hex heads  48  and  54 . The socket  64  allows a hex head to pass therethrough in a manner that selected of the gripping surfaces  72  are juxtaposed in close gripping relation with corresponding sidewalls of the hex head. 
     Desirably, the tension adjusting tool or socket wrench  60  may be used in a confined area with limited turning space, as is presented in the motorcycle herein. Preferably, the gripping surfaces  72  form a 12-point (double-hexagon) configuration, which doubles the number of starting positions which may be used to position the tool for use. Additionally, the gripping surfaces  72  may form a 6-point (hexagonal) configuration. While a hexagonal configuration or shape is preferred, the shape may be other than hexagonal. 
     The actuator rod  66  is axially elongated, has lower and upper end portions  66   a  and  66   b , and an exterior surface, at least in part, provided with thread  76 . The actuator rod  66  is threadably engaged with the threaded bore  74  and generally perpendicular thereto. Upon rotation, the actuator rod is axially movable relative to the lever end portion  70 . A foot  78  of non-abrasive material, such as nylon, is fixedly attached to the lower end portion  66   a  of the actuator rod. A hexagonal shaped drive nut  80  is fixedly attached to the upper end portion  66   b  of the rod. 
     In use, and turning to  FIGS. 6 and 7 , the ends  26   a  and  26   b  of the driven shaft  26  are positioned in the axle slots  36  of the respective fork members  20  and  22  and the cams  40  are positioned against their respective end faces  42  of the cam guides  38 , The connection is such that the cams  40  are not tightly pressing against (i.e., in clamped gripping relation) with the fork members  20  and  22 . 
     In  FIG. 6 , the socket wrench  60  is positioned about the hex head  48 . The hex head  48  is passed through the socket  64  of double hexagonal configuration and the lever  62  positioned such that the end portion  70  is disposed above the upwardly facing support surface  44 . In the illustration shown, the gripping surfaces  72  are not shown to scale. However, in operation, the gripping surfaces  72  of the socket and sidewalls of the hexagonal shaped head  48  would form a snug engagement. 
     Initially, the actuator rod  66  is positioned such that the foot  78  thereof is proximate to the surface  44 . A turning torque “T” is placed on the hex head  78 , causing the actuator rod  66  to rotate relative to the lever  62  and the plate portion  70 . The interengaging thread  76  of the rod and hex head cause the rod  66  to move vertically downwardly relative to the lever and the foot  78  to engage the support  44 . So positioned, the rod axis is disposed generally perpendicular to the surface  44  and at a location “X 1 ” and the center of the shaft  26  at a location “X 2 ”. 
     Further rotation of the rod  66  relative to the plate portion  70  causes the lever  62  to rotate upwardly, by an angle “A”, the plate portion  68  causing the hex head  48  and the cam  40  to rotate. The spiral outer periphery  46  of the cam  40  engages the vertical surface  42 , causing the ends  26   a  and  26   b  of the axle  26  to be driven in the slot  36  in a direction away from the face  42 . 
     Simultaneously, and by the action of this lever action, the cam on the other side  26   b  of the shaft  26  is caused to rotate. The outer periphery of the cam on the side  26   b  rotates against the end face  42  on that side and the shaft  26 , and the spiral outer periphery of the cam forces the shaft to be driven in the slot associated therewith in a direction away from the end face  42 . 
     Rotation of the lever  62  causes shaft  26  to be horizontally driven in the slots  36  in a direction away from the face  42 , and the shaft ends  26   a  and  26   b  are moved in equal amounts. The axes of the axle  26  and the rotatable sprockets  30  and  32  are maintained substantially in parallel relation to one another. 
     As shown in  FIG. 7 , the actuator rod  66  has been rotated, by an amount desired, necessary to rotate the lever  62  and move the cam and shaft to the right. So moved, the socket wrench immobilizes the driven shaft  26  in a position wherein the desired tension is established. 
     The rod  66  has moved to a new position “X 3 ” and the shaft has moved to a new position “X 4 ”, or a distance “D”. This “rightward” movement thereby sets the desired tension in the drive belt. 
     Thereupon, the hex head  54  is completely tightened against the cam  40 , at the shaft end  26   b , and the two cams are driven towards one another and into clamped engagement with their respective forks  20  and  22 . 
     Thereupon, the socket wrench or tool  60  is removed from the hex head. 
     Note should be made that the foot  78  is comprised of a tough material, in that the material must withstand axial loads when bearing against the cam guide  38  and rotational forces occasioned by the torques placed on the rod  66 . However, to obviate scratching the surface  44 , the foot  78  is comprised of a material having sufficient lubricity to permit the rod  66  to translate across the surface  44  without causing scratch marks to the motorcycle exterior surface. 
     Although the invention has been described relative to specific embodiments thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.