Abstract:
A tension management system for generating tension in an endless track of a tracked work machine. The tension management system comprises a biasing element, an idler wheel, a swing link, an idler arm, and a pivotal bracket linking the biasing element with the idler arm. The biasing element generates force that is translated via the biasing arm to the pivotal bracket. The pivotal bracket provides a mechanical advantage in the translation of the force that enables the force exerted upon the swing link to be greater than the force generated by the biasing element. The idler arm connects the pivotal bracket to the swing link and exerts force on the swing link causing it to pivot. The idler wheel is mounted on the swing link and exerts force, generating tension, in the endless track as the swing link pivots. The tension management system enables a greater force to be exerted on the swing link than is generated by the biasing element, allowing for the use of smaller biasing elements than previously possible in conventional designs.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to systems for generating tension in the endless track of a tracked work machine. 
   2. Description of Related Art 
   Tracked work machines are a staple in the military, construction, agriculture, mining, lumber, and other heavy industries. Tracked work machines range in shape and size from tanks and bulldozers to backhoes, mobile cranes, snowmobiles, and robots. These machines are prized for their superior maneuverability over rough terrain, enabled primarily by their tracked means of movement. 
   Such work machines generally comprise a main frame or chassis, an engine or motor, a drive mechanism, and a tension management system. The frame or chassis is the main frame of the machine, upon which the other components are directly or indirectly mounted. For example, the engine or motor is mounted to the main frame. The drive mechanism comprises a drive mechanism frame coupled to the main frame, a drive wheel, an endless track, and a set of rollers or wheels. Two drive mechanisms are typically employed in a tracked work machine, one on each side of the machine. 
   The drive wheel is driven by the engine or motor. The drive wheel is in operative communication with an endless track. Further, the rollers or wheels are distributed along the drive mechanism frame over which the endless track passes. The rollers and drive wheel are distributed to define the path for the endless track to follow. The engine or motor generates rotation of the drive wheel, which in turn results in complimentary rotation of the endless track. 
   Maintaining proper tension of the endless track is necessary for the proper operation of the work machine. If the tension is too low the endless track may buckle, slip off the drive wheel and rollers, jump between teeth on a sprocket drive wheel or roller, or not generate enough friction with the drive wheel to allow for rotation. Alternatively, if the tension is too high, premature wear may occur in components of the drive mechanism. 
   It is also important for the tension to be readily adjustable to prevent damage caused by debris passing between the endless track, and drive wheels, and rollers. Proper tension is also necessary for maintaining balance and stability during uphill or downhill movement, and during digging or other operations. 
   The tension management system of the tracked work machine maintains tension in the endless track of the drive mechanism. The tension management system comprises an idler wheel, a biasing element, and intermediary components for translating force from the biasing element to the idler wheel. The idler wheel is coupled to the drive mechanism frame in a manner that enables its position to be adjusted, which provides regulation for the tension in the endless track. The idler wheel is coupled to the biasing element, which generates force and adjusts the idler wheel&#39;s position. The biasing element presses the idler wheel against the endless track to increase tension in the endless track. The biasing element also actively or passively enables the idler wheel to ease away from the endless track to reduce tension in the track. 
   The large size and heavy loads of work machines require relatively high tension in the endless tracks. The connection between the biasing element and the idler wheel of the tension management system in conventional tension management systems is directly linear.  FIG. 1  illustrates such conventional systems wherein a biasing element  10  is directly connected to a swing link  20 . The force from the biasing element is translated in a linear manner. Examples of such arrangements of the idler wheel and biasing element in the prior art can be found in U.S. Pat. No. 7,172,257 to Tamaru et al. and U.S. Pat. No. 5,851,058 to Humbek et al. The biasing element in such conventional work machines is often a hydraulic or pneumatic pump or a set of powerful springs. Such elements are expensive and prone to frequent damage, necessitating repair or replacement due to the extreme forces being generated. 
   Until now, there has existed a need for a tension management system that can maintain proper tension in an endless track using a lightweight, less expensive biasing element than currently known. It is to such a tension management system that the present invention is primarily directed. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a tension management system for the endless track of a work machine. The exemplary embodiments of the present invention provide a tension management system for an endless track of a work machine, wherein the required tension is regulated with a smaller force produced by the biasing element than in conventional systems by employing the mechanical advantage of a pivotal bracket linking the idler wheel and biasing element. 
   An exemplary embodiment of a tension management system according to the present invention comprises an idler wheel, a swing link, an idler arm, a pivotal bracket, a biasing element, and a biasing arm. The components of the tensions management system are coupled to the drive mechanism frame. The biasing element generates force, which moves the biasing arm. The biasing arm is connected to the pivotal bracket. Movement of the biasing arm causes the pivotal bracket to pivot about its connection to the drive mechanism frame. The pivoting of the pivotal bracket translates the force from the biasing element into movement of the idler arm. The idler arm is mounted on the swing link. The swing link is pivotally connected to the drive mechanism frame. As the idler arm moves, it causes the swing link to pivot about its connection to the drive mechanism frame in a direction away from the biasing element. As the swing link pivots, the idler wheel presses against and exerts force on the endless track, generating tension. Conversely, the swing link may pivot toward the biasing element, causing the idler wheel to ease off the track, lessening the tension. 
   In a further aspect of the invention, in the normal working position shown, the distance between the connection point of the pivotal bracket to the drive mechanism frame and connection point of the pivotal bracket to the biasing arm is greater than the distance between the connection point of the pivotal bracket to the drive mechanism frame and connection point of the pivotal bracket to the idler arm. Thus, the biasing arm has a greater moment arm than the idler arm about the connection of the pivotal bracket to the drive mechanism frame. As a result, force generated by the biasing element and exerted upon the pivotal bracket translates into a greater force in the idler arm. This allows for a greater force to be exerted on the swing link than is generated by the biasing element. 
   In a further aspect of the invention, the biasing element may be an air spring. In conventional work machines, an air spring is not capable of generating sufficient force to produce the required tension in the endless track. However, the mechanical advantage of the different moment arms of the present invention&#39;s biasing arm and idler arm enable a greater force to be exerted against the swing link than is generated by the biasing element. This enables the use of biasing elements such as an air spring, which previously would not have been available due to their limited force generation capacity. 
   These and other features as well as advantages, which characterize various exemplary embodiments of the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates the prior art tension management system employed by tracked work machines. 
       FIG. 2  illustrates an exemplary embodiment of a tension management system within a drive mechanism of a work machine. 
       FIG. 3   a - c  illustrate alternate views of an exemplary embodiment of a pivotal bracket of the tension management system. 
       FIG. 4  illustrates an alternate view of an exemplary embodiment of the tension management system within a drive mechanism of a work machine. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The various exemplary embodiments of the present invention provide a tension management system for regulating tension in the endless track of a work machine. An exemplary embodiment of the tension management system includes a pivotal bracket that serves as a lever arm for generating a moment of force that is preferably translated into a force acting upon the idler wheel, to generate tension in the endless track. The pivotal bracket enables a greater force to be exerted on the idler wheel than is generated by the biasing element. 
   An exemplary embodiment of a tension management system comprises an idler wheel, a swing link, an idler arm, a pivotal bracket, a biasing element, and a biasing arm. The biasing element generates force, which moves the biasing arm. The biasing arm is preferably connected to the pivotal bracket. Movement of the biasing arm causes the pivotal bracket to pivot about its connection to the drive mechanism frame. The pivotal bracket is preferably also connected to a swing link by an idler arm. As the pivotal bracket pivots, force is translated from the biasing element to the swing link. The idler wheel is preferably mounted on the swing link. The swing link is preferably pivotally connected to the drive mechanism frame. As the idler arm moves it causes the swing link to pivot about its connection to the drive mechanism frame. As the swing link pivots, the idler wheel exerts force against the endless track, generating tension. 
     FIG. 2  illustrates an exemplary embodiment of the tension management system  200  as employed in cooperation with the drive mechanism  100  of a work machine. The drive mechanism  100  comprises the drive mechanism frame  110 , an endless track  120 , a drive wheel  130 , and rollers  140 . The drive mechanism frame  110  is preferably connected to the main chassis or frame (not shown) of the work machine. Elements of the drive mechanism  100  are either connected to the drive mechanism frame  110  or connected directly to the main chassis or frame. The engine or motor (not shown) of the work machine causes the drive wheel  130  to rotate. The drive wheel  130  is preferably in operative communication with the endless track  120 . Rotation of the drive wheel  130  causes the endless track  120  to rotate around the drive wheel  130 , and rollers  140 . 
   The tension management system  200  comprises a biasing element  210 , a biasing arm  220 , a pivotal bracket  230 , an idler arm  240 , a swing link  250 , and an idler wheel  260 . The biasing element  210  is preferably connected to the frame  110 . The biasing element  210  is a mechanical structure that is capable of generating force that may be translated to another element. It is contemplated that the biasing element  210  could be connected to the frame  110  by telescoping rods. A biasing arm  220  communicates between the biasing element  210  and the pivotal bracket  230  at bracket bias connection  231 . 
   The pivotal bracket  230  is preferably substantially flat and constructed from metal or another suitable material. The pivotal bracket  230  is preferably triangular having a top, bottom, and middle corner or portion. The pivotal bracket  230  is preferably connected to the frame at a bracket frame connection  232 . The idler arm  240  is preferably connected to the pivotal bracket  230  at a bracket idler connection  233 . In other contemplated embodiments, two coplanar pivotal brackets can be employed, and the biasing arm  220 , idler arm  240 , and portion of the drive mechanism frame  110  connected and partially disposed between the two pivotal brackets. 
   The idler arm  240  is preferably also connected to the swing link  250  at an idler arm connection  251 . The swing link  250  preferably comprises a top, middle, and bottom portion. The idler arm connection  251  is preferably located at the top portion of the swing link  250 . The swing link  250  is preferably connected to the frame  110  at a swing frame connection  252 . The swing frame connection  252  is preferably located at the bottom portion of the swing link  250 . The idler wheel  260  is preferably connected to the swing link  250  at a wheel swing connection  253 . Preferably, the idler wheel  260  comprises a bore, and the swing link  250  can comprise a integral pin extending from the swing link  250  into the bore. The wheel swing connection  253  enables the idler wheel  260  to revolve relative to the swing link  250 . In other contemplated embodiments, the swing link  250  can comprise a bore, and the idler wheel  250  comprises an integral pin in communication with the bore. In further embodiments, the swing link  250  and idler wheel  250  can comprise coaxial bores, and a pin may span the two bores to enable rotatable communication. 
   The connections  231 ,  232 ,  233 ,  251 ,  252 , and  253  are preferably pivotal or rotatable. Contemplated fastening means employed in connections  231 ,  232 ,  233 ,  251 ,  252 , and  253  are a pin, bolt, screw, moveable rivet, or other suitable fastener enabling pivotal communication. Other contemplated connection means include coaxial cylindrical bores in the respective elements and corresponding pins inserted through the bores. In other contemplated embodiments, one element may comprise one of more bores and the other element may comprise one or more integral pins in communication with the bores, enabling pivotal communication. 
   The idler wheel  260  maintains contact with the endless track  120 , and its location relative to the drive mechanism defines the tension in the endless track  120 . Force from the biasing element  210  is preferably translated by the tension management system  200  to the idler wheel  260 . This force presses the idler wheel  260  against the endless track  120 , generating tension. The idler wheel&#39;s  260  connection to the swing link  250  enables the position of the idler wheel  260  to be adjusted relative to the components of the drive mechanism  100  as the swing link  250  pivots. The wheel swing connection  253  enables the idler wheel  260  to revolve as the endless track  120  passes over it. 
   As the biasing element  210  generates force, the biasing arm  220  translates toward the pivotal bracket  230 . The movement of the biasing arm  220  exerts a force on the pivotal bracket  230  at the bracket bias connection  231 . This force causes the pivotal bracket  230  to pivot about the bracket frame connection  232 , generating a moment of force. Arrow A in  FIG. 4  illustrates the pivoting of the pivotal bracket  230 . As the pivotal bracket  230  pivots, it exerts a force upon the idler arm  240  at the bracket idler connection  233 . The force causes the idler arm  240  to translate toward the swing link  250 . Movement of the idler arm  240  exerts a force on the swing link  250  at the swing link idler arm connection  251 . The force causes the swing link  250  to pivot about the swing frame connection  252 . Arrow B in  FIG. 4  illustrates the pivoting of the swing link  250 . As the swing link  250  pivots, it causes the idler wheel  260  to press against and exert force upon the endless track  120 , generating tension. 
   The movements described above are bidirectional. The description above demonstrates the biasing element generating force and translating the force to create tension in the endless track  120 . Should a rock or debris enter between the drive wheel  130 , rollers  140 , or idler wheel  260 , the tension would dramatically increase and damage to the endless track  120  could occur, unless the tension is relieved. To prevent such damage the idler wheel  260  is preferably capable of easing away from the endless track  120 . The swing link  250 , idler arm  240 , pivotal bracket  230  and biasing arm  220  would correspondingly move in the opposite direction from that described above. This movement is possible due to the compressible nature of the biasing element  210 . 
   In the normal working position shown, the force exerted on the swing link  250  is preferably greater than the force generated by the biasing element  210 . The force generated by the biasing element  210  is preferably amplified through the mechanical advantage of the pivotal bracket  230 . The biasing element  210  generates force that is translated by the biasing arm  220  and exerted on the pivotal bracket at bracket bias connection  231 . Because pivotal bracket  230  is preferably pivotally connected to the frame at bracket frame connection  232 , the force exerted at bracket bias connection  231  causes the pivotal bracket  230  to pivot or rotate. This rotation results in moments of force at connections  231  and  233 . The moments of force are a function of the force exerted at the connection multiplied by the moment arm of the connection. Because the system is static, the moments of force are equal. The moment arm at bracket bias connection  231  is equal to the bias frame distance D BF , which is the minimum distance between bracket frame connection  232  and the bias arm central longitudinal axis  280 . D BF  is inherently always defined by a line from the bracket frame connection  232  normal to the bias arm central longitudinal axis  280 . Similarly, the moment arm at bracket bias connection  231  is equal to idler frame distance D IF , which is the minimum distance between bracket frame connection  232  and the idler arm central longitudinal axis  290 . D IF  is inherently always defined by a line from the bracket frame connection  232  normal to the idler arm central longitudinal axis  290 . Because the bias frame distance D BF  is preferably greater than the idler frame distance D IF , the force at bracket bias connection  231  translates to a greater force at bracket idler connection  233 . The ratio of the force at bracket idler connection  233  to the force at bracket bias connection  231  is equal to the ratio of bias frame distance D BF  to idler frame distance D IF . 
   The bias frame distance D BF  and the idler frame distance D IF  both vary as the pivotal bracket  320  pivots.  FIG. 3   a  illustrates the distances D BF  and D IF  in a normal working position.  FIG. 3   b  illustrates the distances D BF  and D IF  wherein the pivotal bracket  230  has significantly pivoted counterclockwise. As a result, both D BF  and D IF  have decreased compared to the normal working position.  FIG. 3   c  illustrates the distances D BF  and D IF  wherein the pivotal bracket  230  has pivoted clockwise. As a result, D BF  has decreased and D IF  has increased compared to the normal working position. Since the moment arms of the pivotal bracket  230  change during operation, the mechanical advantage of the pivotal bracket  230  varies correspondingly. Therefore, the ratio of the force at bracket idler connection  233  to the force at bracket bias connection  231 , which equal to D BF /D IF , changes as well during operation. It is clear from  FIGS. 3   a - c  that while the distances D BF  and D IF  change, they remain defined by lines from the bracket frame connection  232  normal to the bias arm central longitudinal axis  280  and idler arm central longitudinal axis  290 , respectively. 
   In an exemplary embodiment, the pivotal bracket  230  is preferably triangular in shape. The connections  231 ,  232 , and  233  are preferably located at or near the corners of the triangle. In other contemplated embodiments, the pivotal bracket  230  may be a different shape other than a triangle. For example, the pivotal bracket may be circular, oblong, elliptical, rectangular, square, polygonal, or another suitable regular or irregular shape. In the contemplated embodiments, the bias frame distance D BF  is preferably also greater than the idler frame distance D IF . 
   In an exemplary embodiment, the components of the drive mechanism  100  and tension management system  200  are preferably metal, such as high tensile steel. Other contemplated embodiments could incorporate components constructed from other metals and alloys such as stainless steel, iron, titanium, glassy metal, amorphous noncrystalline metal, or other suitable materials. 
   In an exemplary embodiment, the biasing element  210  is preferably an air spring. In conventional tension management systems, an air spring would not be capable of generating sufficient force to produce the necessary tension in the endless track. In the various exemplary embodiments of the present invention, the forced generated by the biasing element  210  is preferably magnified by the pivotal bracket  230 . Consequently, a smaller force generated by the biasing element  210  may be sufficient to generate the tension necessary in the endless track  120 . This allows for a smaller biasing element  210 , such as an air spring, to be employed in the tension management system  200  than was possible in conventional designs. A smaller biasing element is advantageous since it is less expensive, lighter, easier to repair, and less prone to damage since it is not subject to large work forces. 
   The air pressure within an air spring can be adjusted to generate a desired spring rate and a corresponding force generated by the air spring. The force generated by the air spring is translated into tension in the endless track as described above. In other contemplated embodiments, the biasing element  210  may be a coiled steel spring, specialty rubber spring, hydraulic cylinder and accumulator combo, electric motor, air cylinder, pneumatic pump, or other element capable of generating force and/or resistance. In a further embodiment of the present invention, shields may be provided around the biasing element  210  to protect it and increase its reliability. In a further embodiment of the present invention, the pivotal bracket may be replaced with a cam mechanism. 
   The embodiments of the present invention are readily ascertainable by one of ordinary skill in the art. Likewise, modifications, substitutions of equivalent parts, and various design choices are also ascertainable. Thus, the following claims are intended to cover the entire scope of the invention as interpreted by a person having ordinary skill in the art and not merely limit the invention to the verbatim incarnation described and illustrated above.