Abstract:
A pivoting chain guide and tensioner assembly for use with an endless chain loop comprising: at least one bracket plate, a tensioner attached to the at least one bracket plate, and a guide attached to the bracket plates. The bracket plate surrounds the chain at least partially between a driving and a driven sprocket and at least one of the plates has a hole for a pivot at a center axis. The tensioner comprises a tensioner arm with a chain sliding face for contacting the outside of the chain and a biasing means. The guide has a chain sliding face that contacts the outside of the chain. When a high local load is applied to the chain, the load is received by the end of the guide, forcing the guide to move away from the chain, such that the bracket plate pivots, moving the tensioner relative to the chain.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention pertains to the field of tensioners. More particularly, the invention pertains to a tensioner that has damping. 
   2. Description of Related Art 
     FIG. 1  shows a prior art chain driving system having a blade tensioner and a guide. A closed loop chain encircles driving sprocket  12  and driven sprocket  10 . Each sprocket  10 ,  12  accelerates and decelerates independently while maintaining forward motion. A fixed guide  14  is attached to a bracket  7  on the tight strand of the chain. Opposite the guide  14  on the slack strand of the chain is a tensioner  16 , which is at least semi-rigidly fixed to the bracket  7  and biased towards the tight strand of the chain. Bolts  18  fasten the bracket containing the tensioner  16  and the guide  14  to the engine block (not shown). 
   When the driving sprocket  12  accelerated or the driven sprocket  10  decelerates, an energy wave or high local load is created in the tight strand of the chain, which travels from the sprocket that changed in velocity toward the other sprocket. The chain  8  attempts to span the distance between the link of the chain in contact with the initiating sprocket to the other sprocket in the shortest possible distance, a straight line. The energy moves through the links on the free strand of the chain until it comes to the end of the guide  14 , which absorbs the energy. As a result from the constant absorption of the high local load the ends of the guide  14  sustains significant wear. The energy wave would be present and show the same characteristics if it was to originate on the slack strand of the chain, although the wave energy may not occur at all depending on how well the tensioner keeps the slack out of the chain and how much damping the tensioner has. 
   One solution to reduce the load that results in the prior art chain driving system is to add damping to the tensioner. One problem associated with adding the required damping to a tensioner is that if the tensioner is softened significantly, it may result in a loss of chain control, since tensioners are specifically designed to apply just enough force to provide adequate chain control. Other solutions are shown in U.S. Pat. Nos. 5,180,340, 5,797,818, and 5,976,922, 6,322,470, as well as U.S. application Ser. No. 2002-0045503 and Japanese Application No. 2003-047652. 
   U.S. Pat. No. 5,180,340 discloses a coil spring attached to a block on the slack side and tight side of the chain that biases an ejector/apex which is located on the inside side of the chain. As force is applied to the ejector/apex, the ejector pivots against the biasing action of the coil spring to swing toward the adjacent sprocket. 
   U.S. Pat. No. 5,797,818 discloses a chain assembly with reduced noise and vibration on the slack side of the chain comprising a blade shoe, a spring, and a resilient damping device. The shoe is pivotally mounted to the tensioner bracket. The spring is mounted to the shoe and biases the shoe towards the chain. The resilient damping device is mounted between the tensioner bracket and the spring to aid in controlling the vibration that occurs during valve events. 
   U.S. Pat. No. 5,976,922 discloses a tensioning device comprising a tension lever that has first and second slide blocks affixed, such that the slide blocks are on either side of the slack side of chain. The first slide block is pivotably attached to a guide rail on the tight side of the chain. The second slide block is biased against one of the sides of the slack side of the chain by a tension element comprising a compression spring and a piston. 
   U.S. Pat. No. 6,322,470 discloses a tensioner that includes a pair of pivoting arms used to simultaneously tension two separate strands of the same chain. A lever with fixed pins is located between the two strands. The arms extend outside the strands of the chain and carry shoes positioned to contact the outside portion of the chain are pivotally mounted to the fixed pins. Rotation of the lever causes the fixed pins to move laterally and the arms draw inward and tension is imparted to the separate chain strands at the same time. In other words, a high load on one side of the chain tries to transfer to the other side of the chain but the load eventually evens out. 
   US 2002-0045503 discloses a chain tensioner that has a blade and spring assembly. The blade has a first end and a second end. The first end defines a hub. The hub is connected to the central portion of the blade shoe and a first end wall and defines a bore that receives a pin that pivotably connects the blade to a mounting bracket. 
   Japanese Application No. 2003-074652 discloses a tensioner in which a support member is turnably pivoted on a center line connected the two sprockets. Attached to the support member are pressing members on either side of the chain at the same time. The damping that occurs of the slack and tight side of the chain is individual to each side of the chain, since each of the pressing members floats relative to the chain. While there is only one pivot present between the two pressing members, the load on one tries to affect the other and the pressing members undulate back and forth on the chain. 
   SUMMARY OF THE INVENTION 
   A pivoting chain guide and tensioner assembly for use with an endless chain loop drivingly connected to a driving sprocket comprising: at least one bracket plate, a tensioner semi-rigidly attached to the at least one bracket plate, and a guide rigidly attached to the at least one bracket plate. The bracket plate surrounds the chain at least partially between the driving sprocket and the driven sprocket and at least one of the bracket plates has a receiving hole for a pivot at a center axis. The at least one bracket plate may pivot clockwise or counterclockwise two degrees. 
   If two bracket plates are present, at least one of bracket plates contains holes for receiving bolts that attach the bracket plate to the engine block. The remaining bracket plate may pivot clockwise or counterclockwise two degrees relative to the other bracket plate. 
   The tensioner comprises a tensioner arm with a chain sliding face for contacting the outside of the chain and a biasing means that biases the tensioner arm towards the chain. The guide has a chain sliding face that contacts the outside of the chain. 
   When a high local load is applied to the chain, the load is received by the end of the guide, forcing the guide to move away from the chain, such that the plurality of bracket plates or the at least one bracket plate pivots on the pivot, moving the tensioner relative to the chain. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  shows a schematic of a prior art chain driving system. 
       FIG. 2  shows a schematic of a single bracket plate pivoting control system shifted two degrees clockwise. 
       FIG. 3  shows a schematic of a single bracket pivot control system shifted two degrees counterclockwise. 
       FIG. 4  shows a schematic of a dual bracket pivot control system. 
       FIG. 5  shows a front perspective view of the dual brackets of the pivot control system. 
       FIG. 6  shows a profile of the dual brackets of the pivot control system. 
       FIG. 7  shows a front perspective view of a first bracket plate of the dual bracket pivot control system. 
       FIG. 8  shows a back perspective view of a first bracket plate of the dual bracket pivot control system. 
       FIG. 9  shows a cut-away cross section of the dual bracket pivot control system. 
       FIG. 10   a  and  10   b,  cross sections of  FIG. 9 , show the interaction between the two bracket plates of the dual bracket pivot control system. 
       FIG. 11  shows a perspective view of the second bracket plate of the dual bracket pivot control system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 2 and 3  show a single bracket  136  pivot control system.  FIG. 2  shows the bracket  136  pivoting counterclockwise and  FIG. 3  shows the bracket  136  pivoting clockwise. With the single bracket pivot control system it is assumed that the engine block (not shown) contains a pivot similar to that shown in  FIGS. 10   a,    10   b,  and  11  and identified as reference numeral  134 . The single bracket plate  136  has a central receiving hole  128  containing a screw or pivot means  120 , which engages the pivot, which is part of the engine block, allowing the bracket plate  136  to pivot clockwise or counterclockwise. 
   When the driving sprocket  112  or the driven sprocket  110  decelerates, the chain  108  will attempt to span the distance between the link of the chain in contact with the initiating sprocket to the other sprocket in the shortest distance possible, a straight line. The energy wave or high local load moves through the links of the chain until it comes to the end of the guide  114 , as in the prior art discussed above. However, unlike in the prior art, the energy causes the end of the guide  114   a,  which is rigidly fixed to the bracket plate  136  to move away from the tight strand of the chain  108 . The movement of the end of the guide  114   a  causes the bracket plate  136  to pivot clockwise relative to the engine block, causing the end of the guide  114   b  to move towards the tight strand of the chain, the end of the tensioner  116   b  closest to the driving sprocket  112  to move away from the slack strand of the chain and the opposite end of the tensioner  116   a,  closest to the driven sprocket  110  to move towards the slack strand of the chain  108 . The movement of the bracket plate  136  equalizes the energy between both ends of the guide  114   a,    114   b  and allows damping of the chain  108  to take place without compromising the tensioner  116 . The specific movement of the chain  108  is not shown. 
   Similarly, if the high local load was received by the end of the tensioner  116   b,  closest to the driving sprocket  112  and caused the end of the tensioner to move away from the slack side of the chain, this in turn would cause the bracket plate  136  to pivot clockwise relative to the engine block, resulting in the opposite side of the tensioner  116   a  moving towards the slack strand of the chain, the end of the guide  114   a,  closest to the driven sprocket  110  to move away the tight strand of the chain, and the opposite side of the guide  114   b  to move towards from the tight strand of the chain. 
   When the driving sprocket  112  or the driven sprocket  110  accelerates, the chain  108  will attempt to span the distance between the link of the chain  108  in contact with the initiating sprocket to the other sprocket in the shortest distance possible, a straight line. The energy wave or high local load moves through the links of the chain until it comes to the end of guide  114 , as in the prior art discussed above. However, unlike in the prior art, the energy causes the end of the guide  114   b,  which is rigidly fixed to the bracket plate  136  to move away from the tight strand of the chain  108 . The movement of the end of the guide  114   b  causes the bracket plate  136  to pivot counterclockwise relative to the engine block, causing the end of the guide  114   a  to move towards the tight strand of the chain, the end of the tensioner  116   b  closest to the driving sprocket  112  to move towards the slack strand of the chain and the opposite end of the tensioner  116   a,  closest to the driven sprocket  110  to move away from the slack strand of the chain  108 . The movement of the bracket plate  136  equalizes the energy between both ends of the guide  114   a,    114   b  and allows damping of the chain  108  to take place without comprising the tensioner  116 . The specific movement of the chain  108  is not shown. 
   Similarly, if the high local load was received by the end of the tensioner  116   a,  closest to the driven sprocket and caused the end of the tensioner to move away from the slack side of the chain, this in turn would cause the bracket plate  136  to pivot counterclockwise relative to the engine block resulting in the opposite side of the tensioner  116   b  moving towards the slack strand of the chain, the end of the guide  114   a,  closest to the driven sprocket  110  to move towards the tight strand of the chain, and the opposite side of the guide  114   b  to move away from the tight strand of the chain. 
   In an alternative embodiment, dual bracket plates may be used in the pivot control system. Referring to  FIG. 4 , an endless chain loop  108  encloses and drivingly connects a driven sprocket  110  and a driving sprocket  112  with some distance between the two sprockets. On the tight strand of the chain is a guide  114  and on the slack strand of the chain is a tensioner  116 . The guide  114  is rigidly fixed to a first bracket plate  122 , while the tensioner  116  is only partially fixed to the first bracket plate  122 . The tensioner  116  comprises a tensioner arm and a leaf spring (not shown) that rotates with the tensioner arm, which biases the tensioner arm&#39;s chain sliding face towards the outside of the endless chain loop. The guide  114 , opposite the tensioner has a chain sliding face for contacting the outside of the chain loop. 
   The first bracket plate  122  as shown in  FIGS. 5 ,  6 ,  7 , and  8 , has a central hole  128  on a center axis for receiving a screw  120 . The second bracket plate  124 , as shown in  FIGS. 5 ,  6 ,  9   10 , and  11  is fixedly attached to the engine block (not shown) with bolts  126 , preferably cap screws and contains pivot  134  for receiving screw  120 . The first bracket plate  122  fits directly in front of the second bracket  124 , such that the pivot  134 , integral to second bracket  124  receives screw  120 . 
   As described in the previous embodiment, when the driving sprocket  112  or the driven sprocket  110  decelerates, the chain  108  will attempt to span the distance between the link of the chain in contact with the initiating sprocket to the other sprocket in the shortest distance, a straight line. The energy wave or high local load that results causes the end of the guide  114   a,  which is rigidly fixed to the first bracket plate  122  to move away from the tight strand of the chain  108 . The movement of the end of the guide  114   a  causes the first bracket  122  to pivot clockwise relative to the second bracket plate  124 , causing the end of the guide  114   b  to move towards the tight strand of the chain, the end of the tensioner  116   b  closest to the driving sprocket  112  to move away from the slack strand of the chain and the opposite end of the tensioner  116   a,  closest to the driven sprocket  110  to move towards the slack strand of the chain  108 . The movement of the first bracket plate  122 , relative to the second bracket plate  124  is achieved only when the screw  120  engages pivot  134  of the second bracket plate  124  and equalizes the energy between both ends of the guide and allows damping of the chain  108  to take place without compromising the tensioner  116 . The specific movement of the ends of the guide and tensioner are not shown but are similar to those shown in  FIGS. 2 and 3 . 
   Similarly, if the high local load was received by the end of the tensioner  116   b,  closest to the driving sprocket  112  and caused the end of the tensioner to move away from the slack side of the chain, this in turn would cause the first bracket plate  122  to pivot clockwise relative to the second bracket plate  124  resulting in the opposite side of the tensioner  116   a  moving towards the slack strand of the chain, the end of the guide  114   a,  closest to the driven sprocket  110  to move away the tight strand of the chain, and the opposite side of the guide  114   b  to move towards from the tight strand of the chain. 
   When the driving sprocket  112  or the driven sprocket  110  accelerates, the chain  108  will attempt to span the distance between the link of the chain  108  in contact with the initiating sprocket to the other sprocket in the shortest distance possible, a straight line. The energy wave or high local load moves through the links of the chain until it comes to the end of guide  114 , as in the prior art discussed above. However, unlike in the prior art, the energy causes the end of the guide  114   b,  which is rigidly fixed to the first bracket plate  122  to move away from the tight strand of the chain  108 . The movement of the end of the guide  114   b  causes the first bracket plate  122  to pivot counterclockwise relative to the second bracket plate  124 , causing the end of the guide  114   a  to move towards the tight strand of the chain, the end of the tensioner  116   b  closest to the driving sprocket  112  to move towards the slack strand of the chain and the opposite end of the tensioner  116   a,  closest to the driven sprocket  110  to move away from the slack strand of the chain  108 . The movement of the first bracket plate  122 , relative to the second bracket plate  124  is achieved only when the screw  120  engages pivot  134  of the second bracket plate  124  and equalizes the energy between both ends of the guide and allows damping of the chain  108  to take place without compromising the tensioner  116 . The specific movement of the ends of the guide and tensioner are not shown but are similar to those shown in  FIGS. 2 and 3 . 
   Similarly, if the high local load was received by the end of the tensioner  116   a,  closest to the driven sprocket and caused the end of the tensioner to move away from the slack side of the chain, this in turn would cause the first bracket plate  122  to pivot counterclockwise relative to the second bracket plate  124 , resulting in the opposite side of the tensioner  116   b  moving towards the slack strand of the chain, the end of the guide  114   a,  closest to the driven sprocket  110  to move towards the tight strand of the chain, and the opposite side of the guide  114   b  to move away from the tight strand of the chain. 
   For the above embodiments, any tensioner, mechanical or hydraulic may be used as long the tensioner arm and the means for forcing the tensioner arm to tension the chain rotate together. 
   Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.