Patent Publication Number: US-2021179210-A1

Title: Ground-engaging track system and pocketed idler for same

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a ground-engaging track system, and more particularly to a track link and an idler structured for anti-scalloping. 
     BACKGROUND 
     A variety of machines utilize tracks as ground-engaging propulsion elements, notably track-type tractors. Sucks tracks typically have a plurality of rotatable track-contacting elements, including one or more idlers, track rollers, a drive sprocket, and carrier rollers. Each of two tracks at opposite sides of the machine include track links arranged in track chains forming endless loops moved about the rotating track-contacting elements during operation. Demands placed upon such machines and their associated tracks during service can be quite substantial, with high torsional loads, shearing loads, impacts, and others. Ground-engaging tracks are commonly robustly built to provide an operating life of hundreds, even more preferably thousands, of field service hours despite significant stresses, strain, and material wear. 
     Understanding and managing wear phenomena in machine tracks has received considerable engineering attention in recent years. The wear phenomena and wear rates experienced by machine track are typically a result of how the machine is used, the skill and experience of the operator, and the particular underfoot conditions and substrate materials in the operating environment. Machines operated in sandy materials, for instance, tend to experience component wear relatively more rapidly than machines used in soil and/or clay, coal, landfill waste, or hard rock environments. Field service life of machine track tends to vary based upon the factors mentioned above as well as the design of the track components themselves. 
     Machine track components can be relatively expensive to service and replace, and require machine downtime, and thus engineering efforts in this field have often focused on reducing and managing wear between and among components. Track links can experience a well-known wear phenomena known as “scalloping,” where a center region of the track link wears relatively rapidly. Tracks that have experienced scalloping wear will tend to have lost relatively more material in the center region than toward the ends, resulting in an uneven track rail surface. The rotating elements contacting a scalloped track will tend to bump up and down, potentially affecting ride quality and, in some instances, impacting the quality of work efforts such as grading that are performed by the machine. Some tractor types tend to be more susceptible than others to degradation of performance and/or ride quality than others. One strategy for addressing scalloping is set forth in U.S. Pat. No. 9,045,180, where track links are formed such that their upper rail surfaces include sacrificial wear material in a convex longitudinal profile that delays scallop formation. 
     SUMMARY OF THE INVENTION 
     In one aspect, a ground-engaging track system includes a track having a first track chain, a second track chain, and a plurality of track pins coupling the first track chain to the second track chain. The track system further includes an idler structured from mounting to a track roller frame, and having an idler body defining an axis of rotation, and an outer idler rim extending circumferentially around the axis of rotation. The first track chain and the second track chain each include track links in an end-to-end arrangement and including, respectively, a first track rail and a second track rail. The track links in the first track chain and the second track chain each include a lower shoe-mounting surface, an upper rail surface forming a segment of the respective first track rail and second track rail, and an inboard link body side. The track links in the first track chain and the second track chain each further include an inboard rail protrusion extending from the inboard link body side, and the upper rail surfaces each include an anti-scalloping bump-out formed upon the respective inboard rail protrusion. 
     In another aspect, an idler for a ground-engaging track system includes an idler body having a central bore, defining an axis of rotation extending between a first axial idler body end and a second axial idler body end, structured to receive a support shaft for rotatably mounting the idler in a track roller frame. The idler body further includes an outer idler rim having a central flange projecting radially outward, and flanked by a first rail contact surface extending axially inward from the first axial idler body end and a second rail contact surface extending axially inward from the second idler body end. A first set of pockets are formed in the central flange adjacent to the first rail contact surface and arranged in a regular circumferential distribution about the axis of rotation. A second set of pockets are formed in the central flange adjacent to the second rail contact surface and arranged in a regular circumferential distribution about the axis of rotation. 
     In still another aspect, an idler for a ground-engaging track system includes an idler body having a central bore, defining an axis of rotation extending between a first axial idler body end and a second axial idler body end, structured to receive a support shaft for rotatably mounting the idler in a track roller frame. The idler body further includes an outer idler rim extending axially between the first axial idler body end and the second axial idler body end. A first set of pockets are formed in the outer idler rim and arranged in a regular circumferential distribution about the axis of rotation. The first set of pockets each open in a radially outward direction, and in a first axial direction, to receive inboard rail protrusions of track links in a first track chain. A second set of pockets are formed in the outer idler rim and arranged in a regular circumferential distribution about the axis of rotation. The second set of pockets each open in a radially outward direction, and in a second axial direction, to receive inboard rail protrusions of track links in a second track chain extending in parallel with the first track chain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a portion of a ground-engaging track system, according to one embodiment; 
         FIG. 2  is another diagrammatic view of a portion of the ground-engaging track system of  FIG. 1 ; 
         FIG. 3  is a side view of a track link, according to one embodiment; 
         FIG. 4  is a perspective view of a track link, according to one embodiment; 
         FIG. 5  is a top view of a track link, according to one embodiment; 
         FIG. 6  is an end view of a track link, according to one embodiment; 
         FIG. 7  is a perspective view of an idler, according to one embodiment; 
         FIG. 8  is a side view of an idler, according to one embodiment; 
         FIG. 9  is a sectioned view through a portion of an idler, according to one embodiment; and 
         FIG. 10  is a perspective view of a portion of an idler, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , there is shown a ground-engaging track system  10  for a machine, according to one embodiment. Ground-engaging track system (hereinafter “track system  10 ”) can be used in a track-type tractor having field service applications in construction, mining, forestry, or other industries. Track system  10  includes a track  12  having a first track chain  14  and a second track chain  16 , and is structured to form an endless loop extending about a plurality of rotatable track-contacting elements. First track chain  14  and second track chain  16  each include track links  36  and  38 , respectively, in an end-to-end arrangement, and having, respectively, a first track rail  40  and a second track rail  42 . Referring also to  FIG. 2 , track  12  includes a plurality of track pins  18  coupling first track chain  14  to second track chain  16 . Track links  36  and track links  38  in first track chain  14  and second track chain  16  each include a lower shoe-mounting surface  44 , illustrated in a track link  36  of track chain  14  in  FIG. 2 , and an upper rail surface  46  and  47 , respectively. Upper rail surface  46  and upper rail surface  47  form segments of the respective first track rail  40  and second track rail  42 . 
     Also depicted in  FIG. 1  is a track roller frame  22 , and a track roller  24  coupled by way of mounts  26  to track roller frame  22  using bolts  28 . Track system  10  can be a so-called hard-bottom track system for a hard-bottom tractor, where track roller  24 , and other track rollers not illustrated in  FIG. 1 , are rigidly mounted to track roller frame  22 . Hard-bottom tractors are commonly used in applications where a substrate material in a work area is graded to a relatively level, or relatively precisely contoured, elevation. With the appropriate use of monitoring and control equipment, and operator skill, hard-bottom tractors have been demonstrated to be well suited for such applications including construction sites, golf courses road and parking lot substrates, and still others. Such applications can differ from those of tractors where a suspension system is provided for managing shocks and vibrations that can be transmitted between a track and a track roller frame by way of track rollers or other components. As will be further apparent from the following description, track system  10  is adapted for retarding scallop formation in track links  36  and  38  over time, implementing design strategies for hard-bottom tractors where certain known anti-scalloping techniques may be undesirable or inferior. 
     Ground-engaging track shoes  20  may be attached to first track chain  14  and second track chain  16 , and in the illustrated embodiment utilize bolts  30  extending through track links  36  and  38 , and through track shoes  20  and nuts  32  in a generally conventional manner. Track roller  24  rotates in contact with first track rail  40  and second track rail  42 , and includes roller flanges  34  that are positioned outboard of first track rail  40  and second track rail  42 , while track roller  24  and other track rollers not illustrated support a majority of a weight of the associated machine. Track links  36  and  38  in first track chain  14  and second track chain  16  each further include an inboard rail protrusion  48  and  49 , respectively, extending from inboard link body sides of track links  36  and  38 . Upper rail surfaces  46  and  47  each include an anti-scalloping bump-out  50  and  51 , formed upon the respective inboard rail protrusions  48  and  49 . In the illustrated embodiment track links  36  and  38  are mirror images of one another, and description of track links  36  should be understood to refer by way of analogy to track links  38 . Moreover, description of a track link  36  in the singular should be understood to refer to any of the track links in first track chain  14 , or in track chain  16 . In the illustration of  FIG. 2 , shoe bolting bores  35  are shown as they might appear with the associated track shoe  20  removed. Also shown in  FIG. 2  is an idler  110  having an outer idler rim  116 . Idler  110  may be designed to rotate passively in contact with first track rail  40  and second track rail  42 , and is specially shaped to accommodate anti-scalloping bump-outs  50  and  51 , as further discussed herein. 
     Referring now to  FIGS. 3 and 4 , there are shown features of track link  36  in additional detail. Track link  36  includes an elongate link body  52  having an inboard link side  54 , an outboard link side  56 , a first link strap  58 , and a second link strap  61 . First link strap  58  has a first track pin bore  60  formed therein and extending between inboard link side  54  and outboard link side  56 . Second link strap  61  has a second track pin bore  62  formed therein and extending between inboard link side  54  and outboard link side  56 . Elongate link body  52  further includes a middle section  64 . Upper rail surface  46  includes a central pad  66  formed on middle section  64 . A first leg  68  of upper rail surface  46  extends from central pad  66  onto first link strap  58 . A second leg  70  of upper rail surface  46  extends from central pad  66  onto second link strap  61 . As noted above, track link  36  also includes an inboard rail protrusion  48 . Inboard rail protrusion  48  projects from inboard link side  54 . Central pad  66  includes an anti-scalloping bump-out  50  formed on inboard rail protrusion  48 . During operation, idler  110  may slide into and out of contact with upper rail surface  46 , giving rise to a relatively greater rate of material wear generally toward a middle part of central pad  66  as compared to first leg  68  and second leg  70 , and other parts of central pad  66  not subjected to sliding contact. First leg  68  and second leg  70  are laterally offset from one another, and first leg  68 , second leg  70 , and central pad  66  define a common plane. The relatively greater rate of material wear upon central pad  66  would, unless ameliorated, tend to give rise to scallop formation earlier than is desired, ultimately causing upper rail surface  46  to assume a concave form, potentially affecting ride quality and/or machine performance. As further discussed herein, inboard rail protrusion  58 , and in particular anti-scalloping bump-out  50 , provides additional available wear material by way of locally increased surface area that retards scallop formation in response to contact with idler  110 . Since sliding contact tends not to occur, or significantly less so, when idler  110  comes into and out of contact with first leg  68  and second leg  70  than with parts of central pad  66 , the rate of material wear upon first leg  68  and second leg  70  can be relatively slow, and these parts of upper rail surface  46  can be considered relatively scalloping-insensitive compared to regions where sliding contact does occur. Analogously, parts of central pad  66  adjacent to first leg  68  and second leg  70  can also be relatively scalloping-insensitive. Central pad  66  may thus be understood to have a scalloping-insensitive first region  96  adjacent to first link strap  58 , and a scalloping-insensitive second region  98  adjacent to second link strap  61 . Central pad  66  is also understood to include a scalloping-sensitive middle region  99  that extends longitudinally between scalloping-insensitive first region  96  and scalloping-insensitive second region  98 . Scalloping-sensitive middle region  99  includes a diameter that is enlarged, relative to diameters of scalloping-insensitive first region  96  and scalloping-insensitive second region  98 , as further discussed herein, to provide the locally enlarged anti-scalloping surface area for retarding scalloping of upper rail surface  46  in response to contact with idler  110 . 
     Referring also now to  FIG. 5  and  FIG. 6 , upper rail surface  46  includes an outboard edge  72  and an inboard edge  74 , and defines a latitudinal midline  76  extending between inboard edge  74  and outboard edge  72 . Anti-scalloping bump-out  50  extends fore and aft of latitudinal midline  76 . In a practical implementation strategy, anti-scalloping bump-out  50  is centered fore-aft, and symmetrical, about latitudinal midline  76 . It can also be noted, particularly in reference to  FIG. 5 , that outboard edge  72  has an outboard edge profile extending substantially an entirety of a longitudinal length of central pad  66  and first leg  68 , that is linear. Inboard edge  74  includes an inboard edge profile having a first linear segment  78 , a second linear segment  80 , each parallel to the outboard edge profile, and a bumped-out segment  82  extending between first linear segment  78  and second linear segment  80 . A first nut seat window  84  and a second nut seat window  86  are formed in middle section  64  on opposite sides of latitudinal midline  76 . First linear segment  78  overlaps, longitudinally, with first nut seat window  84 . Second linear segment  80  overlaps, longitudinally, with second nut seat window  86 . At least a portion of inboard rail protrusion  48 , is longitudinally between first nut seat window  84  and second nut seat window  86 . It can also be noted from  FIG. 5  that a latitudinal first line  92  is defined at a first origin  93  of anti-scalloping bump-out  50 , corresponding to an intersection of bumped-out segment  82  and first linear segment  78 . A latitudinal second line  94  is defined at a second origin  95  of anti-scalloping bump-out  50 , corresponding to an intersection of bumped-out segment  82  and second linear segment  80 . Scalloping-insensitive first region  96  can be understood as the region of upper rail surface  46  and central pad  66  that extends between latitudinal first line  92  and first leg  68 . Scalloping-insensitive second region  98  can be understood as the portion of upper rail surface  46  and central pad  66  that extends from latitudinal second line  94  to second leg  70 . An anti-scalloping surface area of central pad  66  is defined by central pad  66  as bounded fore-aft by latitudinal first line  92  and latitudinal second line  94 . A first corner or transition  101  adjoins first linear segment  78  and transitions to first leg  68 . A second corner or transition  102  is generally opposite to first transition  101  upon track link  36 . 
     It will be recalled that scalloping-sensitive middle region  99  has a diameter that is enlarged, relative to diameters of scalloping-insensitive first region  96  and scalloping-insensitive second region  98 , providing an enlarged or expanded anti-scalloping surface area for retarding scalloping of upper rail surface  46  in response to contact with idler  110 . With continued reference to  FIG. 5 , there is shown at numeral  88  the bumped-out diameter formed by central pad  66  within anti-scalloping bump-out  50 . A second diameter  90  is formed by central pad  66  outside of anti-scalloping bump-out  50 .  FIG. 5  shows in dashed lines one example range of bumped-out diameter  88  relative to second diameter  90 . In other words, it has been discovered that a range of diameters formed by anti-scalloping bump-out  50  can be well-suited to provision of the enlarged surface area for retarding scalloping while balancing factors such as link size and shape, manufacturability, and compatibility with other components of track system  10  as further discussed herein. 
     In one practical implementation strategy, a ratio of bumped-out diameter  88  to second diameter  90  is from 1.2:1 to 1.6:1. In a refinement, the ratio of bumped-out diameter  88  to second diameter  90  is from 1.3:1 to 1.4:1. As discussed above, the anti-scalloping surface area is bounded fore-aft by latitudinal first line  92  and latitudinal second line  94 . Anti-scalloping bump-out  50  may form from 15% to 30% of the anti-scalloping surface area that is, the total surface area of upper rail surface  46  between lines  92  and  94 . In a refinement, anti-scalloping bump-out  50  forms from 17% to 19% of the anti-scalloping surface area. In one more specific example, a fore-aft running length between origin  93  and origin  94  may be about 4 millimeters. Bumped-out diameter  88  in this example may be about 6 millimeters, and second diameter  90  may be about 24 millimeters. It will further be appreciated that second diameter  90  in scalloping-insensitive first region  96  may be equal to an analogously defined diameter in scalloping-insensitive second region  98 . The term “about” can be understood to be approximate, as will be understood by one in the relevant art, or within measurement error. Bumped-out segment  82  forms a boundary of the locally enlarged surface area. 
     Turning now to features of idler  110 , and in reference now to  FIGS. 7-10 , idler  110  may be structured for mounting to track roller frame  22 , and includes an idler body  112  defining an axis of rotation  114 . Idler body  112  is one-piece in the illustrated embodiment, but could include an idler hub with one or more attached outer rim pieces in others. Idler  110  also includes an outer idler rim  116  extending circumferentially around axis of rotation  114 . It will be recalled, as noted in reference to  FIG. 2 , that idler  110  may be structurally designed to be compatible with the inboard profiles of track links  46  and  48  in first track chain  14  and second track chain  16 . Axis of rotation  114  extends between a first axial idler body end  120  and a second axial idler body end  122 , with central bore  118  being structured to receive a support shaft for rotatably mounting idler  110  in track roller frame  22 . Outer idler rim  116  includes a central flange  124  projecting radially outward, and flanked by a first rail contact surface  126  extending axially inward from first axial idler body end  120  and a second rail contact surface  128  extending axially inward from second axial idler body end  122 . A recess  142  is formed at a first axial side of idler body  112 , and a second recess  144  is formed at a second axial side of idler body  112 . A thin web  146  extends radially inward from outer idler rim  116 . Central flange  124  includes a cylindrical outer flange surface  148 . A first set of pockets  130  are formed in central flange  124  adjacent to first rail contact surface  126  and arranged in a regular circumferential distribution about axis of rotation  114 . A second set of pockets  140  are formed in central flange  124  adjacent to second rail contact surface  128  and arranged in a regular circumferential distribution about axis of rotation  114 . 
     First set of pockets  130  and second set of pockets  140  are arranged, respectively, in rolling register with inboard rail protrusions  48  and  49  of track links  46  and  48  in the respective first track chain  14  and second track chain  16 . First set of pockets  130  and second set of pockets  140  are formed in central flange  124  and adjacent, respectively, to first rail contact surface  26  and second rail contact surface  28 . As noted, first set of pockets  130  and second set of pockets  140  are arranged in rolling register with inboard rail protrusions  48  and  49 . Accordingly, as idler  110  rotates in contact with track  12 , with first rail contact surface  126  riding on first track rail  40  and second rail contact surface  128  riding on second track rail  42 , inboard rail protrusions  48  and  49  may be received into and then out of first set of pockets  130  and second set of pockets  140 , respectively. 
     In one implementation, additional pockets  131  are formed in central flange  124  adjacent to first rail contact surface  126 , but positioned not in rolling register with inboard rail protrusion(s)  48 . Analogously, additional pockets  141  may be formed in central flange  124  adjacent to second rail contact surface  128  but not in rolling register with inboard rail protrusions  49 . Pockets  131  may be understood as a third set of pockets and pockets  141  as a fourth set of pockets, with each of third set of pockets  131  and fourth set of pockets  141  indexed to, but not in rolling register with, inboard rail protrusions  48  and  49  of track links  46  and  48  in first track chain  14  and second track chain  16 , respectively. This arrangement can enable idler  110  to be rotated relative to components of track  12  to compensate for wear, for example. Another way to understand this configuration is that some of the pockets in idler  110  that accommodate rail protrusions will receive the inboard rail protrusions during operation, and some will not, but will instead be positioned between inboard rail protrusions of adjacent track links. Pockets  130 ,  131 , and  140 ,  141 , may otherwise be identically shaped and arranged, such that idler  110  can be rotated an amount equal to one track pitch distance, one-half track pitch distance, one-third track pitch distance, et cetera, depending upon the number and arrangement of the pockets, to provide a new interface of idler  110  each time track  12  is serviced. 
     Pockets  130  in the first set and pockets  140  in the second set may be generally identical, but mirror images of one another. Pockets  130  and pockets  140  may each define a pocket running length  154  extending circumferentially around axis of rotation  114 , a pocket axial depth  156 , and a pocket radial depth  158 . Pocket running length  154  may be greater than pocket radial depth  158 , and pocket radial depth  158  may be greater than pocket axial depth  156 . Idler body  112  may further include a first set of side lugs  150  in an alternating arrangement with first set of pockets  130 , and a second set of side lugs  152  in an alternating arrangement with second set of pockets  140 . As noted above, cylindrical outer flange surface  148  is formed on central flange  124 . Side lugs  150  and side lugs  152  each include outer lug faces  162  and  164 , respectively. Outer lug faces  162  and  164  slope from first rail contact surface  126  and second rail contact surface  128 , respectively, in axially inward and radially inward directions toward cylindrical outer flange surface  148 . It can also be noted that first set of pockets  130  each open in a radially outward direction, and in a first axial direction toward first idler body axial end  120 . Second set of pockets  140  each open in a radially outward direction, and in a second axial direction, toward second axial idler body end  122 . Side lugs  150  and side lugs  152  may each have a trapezoidal shape. Pockets  130  and pockets  140  may each have an inverted trapezoidal shape, and form a taper opening in a radially outward direction. With reference in particular now to  FIGS. 9 and 10 , central flange  124  defines a flange axial thickness  160 . A radio of pocket axial depth  158  to flange axial thickness  160  may be from 0.1:1 to 0.3:1. In a refinement, the ratio of pocket axial depth  158  to flange axial thickness  160  is from 0.13:1 to 0.27:1. In one specific example, pocket axial depth  158  may be from about 4 millimeters to about 10 millimeters. These relative proportions and dimensions enable idler  110  to fit with and accommodate tracks such as track  12  equipped with inboard rail protrusions for retarding scalloping. 
     INDUSTRIAL APPLICABILITY 
     Referring to the drawings generally, as track system  10  is operated, track  12  may be advanced about the various rotatable track-contacting elements in forward directions, reverse directions, and started, stopped, and reversed many times. As track  12  rotates about idler  110 , as well as a second idler where used, upper rail surfaces  46  and  47  will contact rail contact surfaces  126  and  128 . Pivoting between links  46  and  48  in the respective track chains  14  and  16  as links  46  and  48  rotate into and out of contact with idler  110  will tend to cause sliding in a contact “patch” that is generally centered about the latitudinal midline of each track link, corresponding to scalloping-sensitive region  99 . The sliding contact wears away material at a relatively greater rate in scalloping-sensitive region  99  than at other locations of upper rail surface  46 . The locally enlarged surface area provided by anti-scalloping bump-out  50  upon inboard rail protrusion  48  provides additional surface area of material to be worn as compared to other parts of the link. Accordingly, even though the wear conditions are relatively more severe at the portions of the links where sliding contact occurs, the effective wear rate into elongate link body  42  from upper rail surface  46  is slowed, ultimately causing the track links to wear more uniformly longitudinally along the upper rail surfaces, and scalloping more slowly than what is typically observed. 
     With regard to idler  110 , in certain known idler configurations, a central flange would contact track links for guiding purposes approximately at a longitudinal center of the track link upon the inboard side. By providing the pocketed configuration in idler  110 , the additional material added to the track links does not obstruct or otherwise interfere with intended track guiding operation, and the locations of such guiding contact are moved, relative to non-pocketed idlers, into the pockets themselves. 
     The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.