Abstract:
According to aspects illustrated herein, there are provided methods and systems for applying continuous tension on a belt/cable system. The automatic tensioning system includes a pivot mechanism and a locking mechanism. The pivot mechanism includes a pivot arm extending between an idler pulley and a pivot point. The idler pulley is mateable with a belt/cable. The belt/cable is routed about the idler pulley. The idler pulley rotates by the movement of the belt/cable, and the pivot arm pivots in an opposing direction from the belt/cable at the pivot point to apply continuous tension to the belt/cable as the pivot arm pivots. The locking mechanism is in communication with the pivot arm to secure the pivot arm in position, and the locking mechanism is adjustable.

Description:
FIELD OF THE INVENTION 
       [0001]    This disclosure generally relates to a tensioning system that continuously maintains proper tension on belt, cable or chain drives. Specifically, this disclosure relates to a pivotable device that provides minimum static tension without limiting the maximum dynamic belt tension. 
       BACKGROUND OF THE INVENTION 
       [0002]    Belt/cable tensioners are generally well known devices that have been used previously in many belt/cable-drive systems to prevent loose belts/cables which give inaccurate control of the driven wheel. In addition, loose belts/cables have a low stiffness, which causes a low servo bandwidth which result in inaccurate control of the driven wheel velocity or position. A tensioner is used to apply a belt-tensioning force which compensates for increases in belt/cable length due to wear and other factors. 
         [0003]    A loading idler is used to countermeasure the loose belt/cables. The idler rides in a slot. A force is applied to the idler, which in turn loads the belt/cable. Springs, air or hydraulic pistons are examples of method of applying a force. However, any of these methods of applying the force results in a lower stiffness of the drive system. The relation between driven wheel angle and motor angle is represented by a softer spring. This introduces more error and a lower servo bandwidth. A solution to this problem is to lock the idler in place after the force has established the tension. However, during the life of the drive system, belts and cables stretch which results in a loose belt/cable with the errors as described above. 
         [0004]    Another type of belt/cable tensioner has a fixed structure such as a pre-tensioned spring mounted on an idler roll or pulley assembly to set the tension in a belt/cable or cable driven system. The idler is locked in place after the tension is preset. A locking mechanism secures the pre-set tension against the stiffness of the spring. However, the belt/cable extends during use and the pre-set tensioner does not compensate for the changes in the belt/cable length during use. 
         [0005]    Another type of tensioner system consists of a ratcheting mechanism. As the belt/cable lengthens the tensioning arm rotates in one direction to the next setting. However, the ratcheting system has an arm that moves in a stepwise motion to move to the next tooth position, there is not a continuous and appropriate distributed force allowed with a ratchet system. 
         [0006]    There is a need for a tensioning system that provides an automatic and continuous force against the belt/cable throughout the use of the belt/cable. There is a need for a tensioning system that insures proper tensioning against the belt/cable to prevent premature stretching and wearing of the belt/cable. There is a need for a tensioning system that insures minimum static belt/cable tension without limiting the maximum dynamic belt/cable tension, thus enabling higher bandwidth servo controls. 
       SUMMARY OF THE INVENTION 
       [0007]    According to aspects illustrated herein, there is provided an automatic tensioning system, including a pivot mechanism and a locking mechanism. The automatic tensioning system provides minimum static belt/cable tension without limiting maximum dynamic belt/cable tension. The pivot mechanism includes a pivot arm extending between an idler pulley and a pivot point. The idler pulley is mateable with a belt/cable, and the belt/cable is routed about the idler pulley. The idler pulley rotates by the movement of the belt/cable. The pivot arm pivots in an opposing direction from the belt/cable at the pivot point to apply the minimum static tension to the belt/cable as the pivot arm pivots. The locking mechanism is in communication with the pivot arm to secure the pivot arm in position. The locking mechanism is adjustable. As the belt/cable stretches, the pivot arm moves so as to maintain the minimum static tension, the automatic locking mechanism prevents the pivot arm from moving in a direction that would decrease the belt/cable tension. 
         [0008]    According to another aspect illustrated herein, there is provided an automatic tensioning mechanism including a pulley mechanism, a locking mechanism and a pivot arm. The pulley mechanism includes a one-way clutch shaped pulley, a pulley rod and a stopper. The rod extends between the pulley and the stopper. The belt/cable extends about the pulley, and the pulley is attached to the pulley rod to allow for free rotation of the pulley. The locking mechanism includes a wedge plate, a wedge element, a pair of rods and a pair of compression springs. The pair of rods extends from the wedge plate. The pair of rods extends through the wedge element. The pair of compression springs extends about the pair of rods. The wedge element is located on the pair of rods between the wedge plate and the pair of compression springs. The pivot arm pivots about a pivot point. The pivot arm is located between the stopper and the wedge element. The pulley rod extends from the pulley through the wedge element, between the pair of springs, through the pivot arm to the stopper. 
         [0009]    According to a further aspect illustrated herein, there is provide a method of automatically providing tension to a cable, including the steps of attaching a belt/cable around an idler pulley, the belt/cable rotates freely about the idler pulley; attaching a pivot arm to the idler pulley, the pivot arm extends between the idler pulley and a pivot point, the pivot arm pivots in an opposing direction from the belt/cable at the pivot point to apply tension to the belt/cable; and applying continuous and adjustable tension to the belt/cable using a locking mechanism. The locking mechanism is in communication with the pivot arm. The locking mechanism applies continuous force against the pivot arm, the pivot aim pivots away from the belt/cable. The idler pulley pulls on the belt/cable until the belt/cable and idler pulley are at rest, and to maintain continuous tension on the belt/cable. 
         [0010]    Additional features and advantages will be readily apparent from the following detailed description, the accompanying drawings and the claims. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows an automatic belt/cable tensioning system of a drive device. 
           [0012]      FIG. 2  shows an automatic belt/cable a tensioning system of a drive device. 
           [0013]      FIG. 3  shows a wedge element of  FIG. 2 . 
           [0014]      FIG. 4  shows an automatic belt./cable tensioning system of a drive device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    The systems disclosed herein use tensioning system which provides the minimum static and proper tension on the belt/cable throughout the usage of the device without limiting the maximum dynamic belt/cable tension. 
         [0016]    As used herein, the phrase “belt/cable” refers to chain, belt, cable, flat belt, timing belt, vee belt, film belt and the like. 
         [0017]    As used herein, the phrase “one-way clutch” refers to uni-directional clutch, freewheeling clutch, overrunning clutch, roller-ramp clutch, sprag clutch, or a member that transmits a drive when input rotated in one direction but releases and freewheels or slips when it is turned in an opposite direction. 
         [0018]      FIG. 1  shows a tensioning system device  10  including a pivot mechanism  12 , locking mechanism  14  and a tension spring  16 . The pivot mechanism  12  includes an elongated pivot arm  18  with an idler pulley  20  mounted at first end  22  and a pivot point  26  at the second end  24 . The pivot arm  18  is generally rectangular in-shape. A belt/cable  28  is routed over and about the idler pulley  20 . The idler pulley  20  is attached to the pivot arm  18  by a fastener  30  such that the idler pulley  20  is able to rotate about the fastener  30  on the pivot arm  18 . A tension spring  16  is attached to the pivot arm  18  between the idler  20  and the pivot point  26 . The tension spring  16  sets the tension in the belt/cable  28 . The tension spring  16  extends between the pivot arm  18  and a support structure(not shown). The pivot point  26  includes an attachment mechanism  32  that is capable of pivotably attaching the pivot arm  18  to the locking mechanism  14 . The pivot point  26  is a hole though the pivot arm  18 , a hole  33  through the locking mechanism  14  and a pin  34  extending therethough connecting the pivot arm  18  to the locking mechanism  14 . As the belt/cable stretches, the tension spring  16  causes the pivot arm  18  to rotate clockwise at the pivot point  26 . The pivot arm  18  pivots away from the locking mechanism  14 , away from the cable motor and in the direction of the force from the tension spring  16  to provide tension in the belt/cable  28 . 
         [0019]      FIG. 1  shows a locking mechanism  14  pivotably attached to the pivot mechanism. The locking mechanism  14  includes an elongated wedge plate  36 , a wedge wing  38  and a pre-loaded wedging element  42 . The wedge plate  36  extends adjacently opposed to the pivot arm  18 . The wedge plate  36  is generally rectangular elongated portion with a top cap  44  and a pivot attachment plate  46 . The cap  44  is attached to the top of the wedge plate  36  and extends beyond the perimeter of the wedge plate  36  on one side such that the cap  44  and the wedge plate  36  have an L-shaped geometry. The pivot attachment plate  46  is on the opposite end of the wedge plate  36  from the cap  44 . The pivot attachment plate  46  is part of the pivot attachment mechanism  32 . The pivot attachment plate  46  is a U-clamp extending from the end of the wedge plate  36 . The pivot arm  18  seats within the pivot plate  46 . The pivot attachment plate  46  has holes  33  therethrough for the pin  34  to attach the pivot arm  18  to the wedge plate  36 , as described above. 
         [0020]    The portion of the cap  44  that extends beyond the wedge plate  36  includes a pre-loaded wedging element  48  attached thereto. The pre-loaded wedging element  48  includes a wedge spring  48  and a wedge element  50 . The spring  48  extends between the wedge element  50  and the cap  44 . The spring  48  applies force to the wedge element  50  and urges the wedge element  50 , between the wedge plate  36  and the pivot arm  18 , towards the pivot point  26 , preventing the pivot arm  18  from rotating counterclockwise. As the tension spring  16  pulls on the pivot arm  18 , the pivot arm  18  is pivoted outwardly away from the wedge plate  36  and the wedge element  50  is forced towards the pivot point  26  locking the pivot arm  18  in place which in turn applies the minimum static tension on the belt/cable  28 . 
         [0021]    The wedge element  50  may be a cylindrical element or other shapes that allow for movement and securement within the angle of the pivot arm  18  and wedge plate  36 . For example, the wedge element  50  can be a round ball, or oblong ball. The wedge angle ranges is about  10  degrees. This prevents the wedging element  50  from being pushed out by the force produced by the belt/cable  28 . Extending from the wedge plate  36  on the opposite side from the pivot arm  18  is a wedge wing  38 .  FIG. 1  shows the wedge wing  38  as a triangular extension piece attached to the wedge plate  36  at the hypotenuse. The wedge wing  38  has an elongated curved mounting slot  52  therethrough and a locking pin  54  extending within the slot  52 . The mounting slot  52  is used to adjust and lock the tensioning system device  10  in place to accommodate different belt/cable lengths. 
         [0022]      FIG. 2  shows a tensioning system device  60  that is similar to the tensioning system  10  of  FIG. 1  including idler pulley mechanism  62 , a pivot mechanism  64  and a locking mechanism  66 . The idler pulley mechanism  62  includes a one-way clutch shaped pulley  68  which engages with the belt/cable  28  about the circumference of the pulley  68 . The pulley  68  is attached to a U-clamp  69 . The U-clamp  69  is attached to the center of the pulley  68  and extends in either side of the pulley  68 . The pulley  68  is allowed to spin freely within the U-clamp  69 . The base  70  of the U-clamp  69  has a rod  71  extending therefrom. The opposite end of the rod  71  from the pulley  68  is a split cylindrical stopper  72 . The rod  71  extends through the curved perimeter of the stopper  72  and exits through the flat surface. The stopper  72  assists in the movement of the pulley mechanism  62 . 
         [0023]    The locking mechanism  66  includes a wedge plate  73 , wedge element  74 , compression springs  75 . The wedge plate  73  is L-shaped with an elongated thicker leg  76  and a shorter thinner base plate  78  extending from one end of the leg  76 . The wedge plate  73  is adjacent the U-clamp  69 . The wedge plate  73  includes attachment points  79  through the leg  76  to attach the wedge plate  73  to a support structure. The wedge plate  73  includes an opening  77  therethrough. The opening  77  permits the rod  71  of the pulley mechanism  62  to extend therethrough. The base plate  78  extends in the opposite direction from the pulley  68 . A pair of parallel, spaced apart rods  80  extends perpendicularly from the base plate  78 . The pair of rods  80  extends parallel to the leg  76  of the wedge plate  73 . The pair of rods  80  includes top caps  81  which have a larger diameter than the rods  80 . Wrapped about each rod  80  is a compression spring  75  with a diameter less than a diameter the top caps  81 . The compression springs  75  extend between the top cap  81  and the wedge element  74 . The wedge element  74  is a generally square cube with one curved side. The wedge element  74  includes a pair of holes  82  which are positioned to allow the pair of rods  80  to extend therethrough. The wedge element  74  is vertically moveable along the length of the rods  80 . The pair of holes  82  have a smaller diameter than the diameter of the compression springs  75  so that the compression springs  75  are unable to enter through the pair of holes  82 . Extending between the pair of rods  80  and below the wedge element  74  is the rod  71  from the pulley mechanism  62 .  FIG. 3  shows the wedge element  74  includes a U-shaped channel  83  through the bottom surface between the pair of holes which allow for the rod  71  of the pulley mechanism  62  to extend therethrough as the wedge element  74  is pushed closer to the base plate  78  by the compression spring  75 . 
         [0024]    The wedge element  74  is sandwiched between the wedge plate  73  and the pivot mechanism  64 . The curved surface  84  of the wedge element  74  is in contact with the pivot mechanism  64 . The pivot mechanism  64  includes an elongated pivot arm  85  and a pivot point  86  at one end. The pivot arm  85  has a U-shaped geometry with a pair of parallel extending sides  87  and a base  88  extending between the pair of sides  87 . The channel  89  of the U-shaped geometry allows for the rod  71  of the pulley mechanism  64  to extend therethrough. The base  88  of the pivot arm  85  is aligned with the base plate  78  of the wedge plate  73  and the extending sides  87  of the pivot arm  85  are in communication with the curved surface  84  of the wedge element  74 . The pivot point  86  extends through the base  88  of the pivot arm  85 . The pivot point  86  is a hole  90  in which a fastener  91  extends therethrough. The fastener  91  attaches the pivot arm  85  to a support structure. The pivot arm  85  is sandwiched between the wedge element  74  and the stopper  72  of the pulley mechanism  62 . The curved surface of the stopper  72  is in communication with the surface of the pivot arm  85 . 
         [0025]    The tensioning system of  FIG. 2  operates in a similar manner as the tensioning system of  FIG. 1 . The compression springs  75  apply a constant downward force against the wedge element  74 . The wedge element  74  is guided downwardly by the pair of rods  80 . The wedge element  74  pushes against the pivot arm  85 . The pivot arm  85  pivots outwardly towards the stopper  72  of the pulley mechanism  62 . The pivot arm  85  applies a force against the stopper  72  which moves the pulley mechanism  62  in the opposite direction from the belt/cable  28  until the forces are equal. Specifically, the force from the belt/cable  28  is equal with the force applied to the stopper  72 . Once the forces are equal the system is at equilibrium and the proper minimum tension is applied to the belt/cable  28 . During use of the belt/cable  28 , the belt/cable  28  will stretch and loosen. The slack in the belt/cable  28  reduces the pull force from belt/cable  28  to the pulley mechanism  62 . Thus, the pulley mechanism  62  is moved toward the pivot arm  85 . The tensioning system  60  migrates to the new equilibrium tension force by having the compression springs  75  move the wedge element  74  down, closer to the base plate  78  of the wedge plate  73 . As the wedge element  74  moves downwardly, it pushes against the pivot arm  85  and forces the pivot arm  85  to rotate counterclockwise. As the pivot arm  85  moves counterclockwise against the stopper  72 , the pulley mechanism  62  is moved closer to the wedge plate  73 . These elements are readjusted until the forces are equal between the tension from the belt/cable and the force from the compression springs  75  restoring the proper minimum tension. 
         [0026]    Additionally, the curved surface  84  of the wedge element  74  allows for the wedge element  74  to migrate down the pivot arm  85  without sticking or slipping, and it allows for the wedge element  74  to lock into place, insuring that the maximum dynamic tension is not a function of the minimum static tension. 
         [0027]      FIG. 4  is another tensioning system  100  that is similar to the previously tensioning systems including a pivot mechanism  102 , locking mechanism  124  and tensioning spring  104 . The tensioning system  100  of  FIG. 4  is designed to fixed to a support structure at the pivot mechanism  102 . The pivot mechanism  102  includes a pivot arm  106  which is generally rectangular in shape with a pulley  108  on the first end  120  and a locking mechanism  124  on the second end  122 . The locking mechanism is a one-way clutch  110 . The pulley  108  is attached to the pivot arm  106  at the rotational point  112 . The belt/cable  28  extends about the pulley  108  and the pulley  108  is free to rotate as the belt/cable  28  moves thereabout. The second end  122  of the pivot arm  106  is a U-shaped end  114  with the one-way clutch  110  located within the channel of the U-shaped end  114 . The one-way clutch  110  is attached to the pivot arm  106  at the pivot point  116 . A pin  118  is inserted through the holes in the pivot arm  106  and the hole in the one-way clutch  110 . The one-way clutch  110  is attached such that it is able to rotate freely in a direction that would tension the belt/cable. Between the first end  120  and the second end  122  of the pulley arm  106  is a tension spring  104  which is attached to a support structure. The tensions spring  104  applies a counterweight force against the tension of the belt/cable  28 . As the tension in the belt/cable  28  reduces the tension spring  104  pulls the pivot arm  106  closer to the support structure, and as the pivot arm  106  is pulled towards the support structure it rolls on the one-way clutch  110  away from the support structure to balance the forces. The one-way clutch  110  provides a locking mechanism by the friction between the surface with the one-way clutch  110  is resting on and the one-way clutch  110 . 
         [0028]    Having described the aspects herein, it should now be appreciated that variations may be made thereto without departing from the contemplated scope. Accordingly, the aspects described herein are deemed illustrative rather than limiting, the true scope is set forth in the claims appended hereto.