Patent Publication Number: US-2023150592-A1

Title: Idler for undercarriage system in track-type machine and wear pad for same

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to an idler in an undercarriage system of a track-type machine, and more particularly to one-piece replaceable idler wear pads for extending idler service life. 
     BACKGROUND 
     Track-type machines are used throughout the world in a great many different off-highway applications. In a typical configuration each of two ground-engaging tracks in a machine includes an endless loop of track links in two parallel track chains extending about rotating elements including one or more idlers and a drive sprocket. Track shoes, commonly equipped with grousers, are attached to the track chains and contact a substrate to propel and steer the machine. In rough, uneven, rocky, steep, and slippery field service environments track-type machines are indispensable for many activities. 
     Due to the nature of substrate materials and service conditions, wear between and among components in an undercarriage system of a track-type machine can be relatively severe. In view of the wear phenomena, and the necessity for generally robust and sophisticated track and undercarriage construction, inspection, servicing, and replacement of undercarriage parts is routine. As noted above, one or more idlers are typically provided which rotate passively in contact with the track as the track advances during service. The idler is commonly arranged to rotate in contact with track rails formed by the parallel chains of track links. Over the course of time material of the contacting components tends to be worn away, eventually requiring replacement of the idler. 
     Various proposals are known for reuse, repair, and otherwise extending idler service life. In commonly owned U.S. Pat. No. 8,770,672 to Yelistratov, an undercarriage system includes an idler having a compound annular rim capping a hub and formed of a relatively higher hardness metallic material. The use of relatively higher hardness metallic material apparently is intended to extend idler service life, and the disclosed techniques can enable replacement of worn-away material in a used idler, for example. While Yelistratov may have various applications and advantages, there is always room for improvement and development of alternative strategies. 
     SUMMARY 
     In one aspect, an idler for an undercarriage system in a track-type machine includes an idler rim having an outer rim surface extending circumferentially around an idler access of rotation and forming a radially projecting central guide flange. The idler further includes a plurality of one-piece wear pads attached to the idler rim upon a first axial side of the radially projecting central guide flange and upon a second axial side of the radially projecting central guide flange. Each of the plurality of one-piece wear pads includes a sacrificial head supported on the outer rim surface and having an outer link-contact surface, and a base in interlocking engagement with the idler rim. 
     In another aspect, an idler for an undercarriage system in a track-type machine includes an idler rim having an outer rim surface extending circumferentially around an idler axis of rotation, and an inner surface forming a shaft bore extending between a first axial idler side and a second axial idler side. The first axial idler side includes a first axial end face extending radially inward from the outer rim surface, and the second axial idler side includes a second axial end face extending radially inward from the outer rim surface. The idler rim further includes a plurality of pad retention channels arranged in a first set extending radially inward from the outer rim surface and axially inward from the first axial end face, and a second set extending radially inward from the outer rim surface and axially inward from the second axial end face. 
     In still another aspect, an idler wear pad for an idler in an undercarriage system includes a one-piece pad body having an elongate sacrificial head including an inner idler-contact surface, and an outer link-contact surface extending fore and aft between a first head end and a second head end and having an arcuate longitudinal profile that is upwardly convex. The one-piece pad body further includes a neck attached to the elongate sacrificial head longitudinally between the first head end and the second head end and extending downwardly from the inner idler-contact surface, and a base extending outwardly from the neck both fore and aft to interlock the one-piece pad body within a pad retention channel in an idler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side diagrammatic view of a portion of an undercarriage system in a track-type machine, according to one embodiment; 
         FIG.  2    is an assembled diagrammatic view of an idler, according to one embodiment; 
         FIG.  3    is a partially assembled diagrammatic view of an idler, as in  FIG.  2   ; 
         FIG.  4    is an enlarged diagrammatic view of a portion of an idler as in  FIGS.  2  and  3   ; and 
         FIG.  5    is a diagrammatic view of an idler wear pad, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , there is shown a track-type machine  10  including an undercarriage system  12 , according to one embodiment. Undercarriage system  12  includes a track roller frame  14 , a drive sprocket  16 , and a plurality of track rollers  18 . A ground-engaging track  20  extends in an endless loop around drive sprocket  16 , track rollers  18 , and an idler  30 . Idler  30  may be a back idler, or a front idler, in a so-called “high drive” track configuration” as shown, in an oval configuration, or still another. In a typical arrangement, track  20  and other components shown in  FIG.  1    are on one side of machine  10 , and analogous components arranged to provide a second ground-engaging track upon an opposite side of machine  10 . Track  20  includes a plurality of coupled-together track links  22  with a plurality of attached track shoes  24 . Track links  22  form a track rail  26  upon which idler  30  and track rollers  18  ride during service. Track rail  26  may be one of two track rails formed by two parallel track chains in track  20 , one of which is visible and formed by track links  22  in the illustrated embodiment. Undercarriage system  12  can be used in a track-type tractor, a track-type loader, or any of a variety of other types of off-highway machines. In a practical implementation strategy machine  10  includes a track-type tractor as might be used for construction, mining, forestry, or a variety of other applications. As will be further apparent from the following description idler  30  is configured with replaceable wear parts for extended service life in undercarriage system  12 . 
     Referring also now to  FIGS.  2  and  3   , idler  30  includes an idler rim  34  having an outer rim surface  36  extending circumferentially around an idler axis of rotation  38  and forming a radially projecting central guide flange  40 . Idler rim  34  may be a one-piece forging of a suitable iron, steel, or other alloy metallic material. During service, guide flange  40  may be received between parallel chains of track links  22  and assists in maintaining idler  30  and track  20  in a desired arrangement. Idler rim  34  may further include an inner surface  48  forming a shaft bore  50  extending between a first axial idler side  52  and a second axial idler side  54 . First axial idler side  52  includes a first axial end face  56  extending radially inward from outer rim surface  36 . Second axial idler side  54  includes a second axial end face  58  extending radially inward from outer rim surface  36 . Idler rim  34  further includes a plurality of pad retention channels  60  arranged in a first set extending radially inward from outer rim surface  36  and axially inward from first axial end face  56 . Pad retention channels  60  are also arranged in a second set extending radially inward from outer rim surface  36  and axially inward from second axial end face  58 . As used herein, the terms “radially inward” and “radially outward” are used according to their common definitions relative to idler axis of rotation  38 . The terms “axially inward” and “axially outward” are understood to mean directions along or parallel to idler axis of rotation  38  toward and away from, respectively, a geometric center point of idler  30  intersected by idler axis of rotation  38 . 
     Idler  30  further includes a plurality of one-piece wear pads  62  attached to idler rim  34  upon a first axial side of radially projecting central guide flange  40  and upon a second axial side of radially projecting central guide flange  40 . One-piece wear pads  62  may each include a forging, a casting, a cut segment of an elongate, shaped forging, for example, or any other suitable body made of a suitable metallic material. Wear pads  62  might also be heat treated or hardened by another process in some embodiments. The metallic material of wear pads  62  may be the same as the material of which idler rim  34  is made, or different. In some embodiments wear pads  62  may include or be formed entirely from a relatively harder material than idler rim  34 . Each of the plurality of wear pads  62  includes a sacrificial head  64  supported on outer rim surface  36  and having an outer link-contact surface  66 , and a base  68  in interlocking engagement with idler rim  34 . Sacrificial head  64  may be elongate in a direction circumferentially around idle axis of rotation  38 . The term “sacrificial” is used in reference to expected and intended wearing away of material of wear pads  62  during service, as further discussed herein. 
     Also shown in  FIGS.  2  and  3    is an idler shaft  42  extending through shaft bore  50  and rotatable journaling idler  30 . Idler shaft  42  will typically be a fixed shaft, with bearings supported between idler shaft  42  and idler rim  34 . In other embodiments, idler shaft  42  could be a live shaft supported for rotation in undercarriage system  12  and rotatably fixed relative to idler rim  34 . A clamping ring  44  or the like can be positioned upon each axial side of idler rim  34  and bolted to idler rim  34  by way of bolts  46  to house and retain thrust and journal bearings, seals, and/or other components within idler  30 . As shown in  FIG.  1   , idler  30  can be supported in support blocks  32  or other suitable apparatus coupled to track roller frame  14 . 
     With focus on  FIG.  3   , each pad retention channel  60  may be formed in part by an undercut surface  70  facing a radially inward direction and spaced radially inward of outer rim surface  36 . Each of pad retention channels  60  may also include a necked-down outer channel section  72  opening in outer rim surface  36  and in the respective first axial end face  56  or second axial end face  58 , and an enlarged inner channel section  74 . Pad retention channels  60  may be formed by machining, during forging, or by way of combination of these or other techniques. Enlarged channel section  74  may be formed in part by undercut surface  70  and opens in the respective first axial end face  56  or second axial end face  58 . Referring also now to  FIG.  4   , in an implementation each of pad retention channels  60  further includes a channel floor  80  opposite to undercut surface  70 , a forward recess  82 , and a rearward recess  84 . Each of pad retention channels  60  may further define an axial length dimension  76  and a radial depth dimension  78  that is equal to or less than axial length dimension  76 . A number of pad retention channels  60  in each of the first set and the second set may be 8 or greater, in a refinement greater than 12, and regularly distributed circumferentially around idler axis of rotation  38 . 
     As noted above, wear pads  62  each include a base  68  in interlocking engagement with idler rim  34 . It is contemplated that a variety of different geometries of wear pads  62  and pad retention channels  60  could provide interlocking to secure wear pads  62  upon idler rim  34 . Polygonal shapes of the respective bases and pad retention channels, non-polygonal shapes, L-shapes, T-shapes as shown, or still another could be employed. In a typical construction wear pads  62  are interlocking with idler rim  34  but removable. Thus, when it is desirable to replace wear pads  62 , the used wear pads  62  can be slid out of pad retention channels  60  in axially outward directions and swapped out for new wear pads. 
     In the illustrated embodiment idler  30  further includes a first pad retainer  112  attached to first axial end face  56  and a second pad retainer  114  attached to second axial end face  58 , each clamping or otherwise retaining a plurality of wear pads  62  within a plurality of pad retention channels  60 . Also in the illustrated embodiment first pad retainer  112  and second pad retainer  114  are bolted to the respective first and second axial end face  56  and  58  by way of bolts  116 . Other attachment strategies for wear pads  62  and/or pad retainers  112  and  114  could be used. For instance, wear pads  62  could be interference-fitted or spot welded. Analogously, pad retainers  112  and  114  could be bolted at locations radially inward from those shown, interference-fitted, or welded. Still other attachment strategies, including reversible and non-reversible attachment strategies, could be employed. A non-reversible attachment strategy would include a mechanism for attachment, which to overcome and decouple the parts, would require cutting or modifying components such that they are not reusable, at least without modification. As depicted in the drawings each of first pad retainer  112  and second pad retainer  114  may include one retaining ring. In other instances, arc segments of a ring, plates, covers, or another structure altogether could be used. 
     Referring also now to  FIG.  5   , there are shown features of a one-piece idler wear pad  62 , according to the present disclosure, in further detail. Wear pad  62  includes outer link-contact surface  66  thereon as described above. Outer link-contact surface  66  may have an arcuate longitudinal profile. Sacrificial head  64  may also include an inner idler-contact surface  88  having an arcuate longitudinal profile parallel to the arcuate longitudinal profile of outer link-contact surface  66 . Idler wear pad  62  may be formed as a one-piece pad body  86 , wherein each of inner idler-contact surface  88  and outer link-contact surface  66  extends fore and aft between a first head end  90  having an end face  92  and a second head end  94  having an end face  96 . A longitudinal cross-sectional shape of sacrificial head  64  may be a rectangular shape. The arcuate longitudinal profile of outer link-contact surface  66  may be upwardly convex, and the arcuate longitudinal profile of inner idler-contact surface  88  may be upwardly concave and matched to an outer profile of outer rim surface  36 . 
     Idler wear pad  62  and one-piece pad body  86 , referred to at times interchangeably herein, further includes a neck  98  attached to sacrificial head  64  longitudinally between first head end  90  and second head end  94  and extending downwardly from inner idler-contact surface  88 . Base  68  may extend outwardly from neck  98  both fore and aft to interlock idler wear pad  62  within a pad retention channel  60  in idler  30 . When interlocked with idler rim  34 , neck  98  and base  68  may be entirely within idler rim  34 , mostly or entirely axially inward of the respective axial end face  56  and  58 . Sacrificial head  64  may likewise be mostly or entirely axially inward of the respective axial end face  56  and  58 , and radially outward of outer rim surface  36 . Sacrificial head  64  may be elongate in the fore and aft direction. When installed for service on idler rim  34  wear pads  62  may be arranged end-to-end upon the first axial side of central guide flange  40  and upon the second axial side of central guide flange  40 . A number of wear pads  62  may be 8 or greater in some embodiments, and in a refinement greater than 12. Sacrificial head  64 , neck  98 , and base  68 , together form a first planar side face  100  and a second planar side face  102  opposite to first planar side face  100 , of one-piece pad body  86 . A pad thickness dimension  104  is defined between first planar side face  100  and second planar side face  102 . A head height dimension  106  that is equal to or less than pad thickness dimension  104  is defined between base  68  and inner idler-contact surface  88 . Base  68  may include a forward projecting retention edge  108  and a rearward projecting retention edge  110 , structured to fit into forward recess  82  and rearward recess  84 , respectively. It can also be seen from the drawings, and  FIG.  5    in particular, that neck  98  and base  68  together form a T-shape. Pad retention channels  60  may also have a T-shape, as noted above. 
     INDUSTRIAL APPLICABILITY 
     Referring to the drawings generally, during service idler  30  will rotate with the advancement of track  20  in forward directions or reverse directions about the various track contacting rotatable elements in undercarriage system  12 . Wear pads  62  will rotate in contact with track rail  26  and the track rail hidden from view in the illustration of  FIG.  1   , with contact between the materials of wear pads  62  and track links  22 , as well as substrate particles and the like, causing material of wear pads  62  in each sacrificial head  64  to wear away. When undercarriage system  12  has reached a desired or a prescribed state of wear, undercarriage system  12  can be disassembled, and idler  30  removed. It is contemplated that wear pads  62  can be swapped out for new wear pads prior to each sacrificial head  64  wearing away entirely, although the present disclosure is not thereby limited. Attachment of first pad retainer  112  and second pad retainer  114  can be reversed, wear pads  62  slid out of pad retention channel  60 , and replacement wear pads installed in their place. Pad retainers  112  and  114 , or replacement pad retainers, can then be reinstalled in idler  30  to secure the replacement wear pads and idler  30  reassembled in undercarriage system  12 . 
     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 kill 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 “a” 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.