Patent Abstract:
A tracked machine may be equipped with a debris guard in order to inhibit entry of debris from an exterior to an interior of a track roller frame. An idler, track roller frame, track and debris guard may be configured to create a difficult to traverse serpentine debris entry pathway into the track roller frame. This may be accomplished by flanking opposite sides of a track chain with a pair of guard plates, and further inhibiting debris entry by including an in board guard shield that defines a slot that surrounds a portion of the idler.

Full Description:
TECHNICAL FIELD 
     The present disclosure relates generally to debris guards for tracked machines, and more particularly to a debris guard for inhibiting entry of debris from an exterior to an interior of a track roller frame. 
     BACKGROUND 
     Track type tractors are one type of machine that utilize an idler recoil system in order to better allow the tracks of the machine to interact with variable loads encountered when the machine is being maneuvered over the ground. A typical track system may include a forward idler that is supported in a track roller frame assembly about which the track is mounted. The track typically includes a series of shoes that contact the ground on one side, and an inner track chain that is driven to rotate to propel the machine in a travel direction. The idler may typically be supported by a yoke that may slide fore and aft within the track roller frame in order to react to various loads that are transmitted from the track to the idler. The yoke in turn acts upon a spring that is compressed when the idler and yoke are pushed into the track roller frame assembly. The spring then recoils back on the yoke and the idler to return both toward their undisturbed operating configuration. 
     Because tracked machines often work in extremely hostile environments that may include mud, sand, rocks, soil and a wide variety of other debris, there is often a risk of debris entering the track roller frame and eventually undermining operation of the recoil system and/or otherwise damaging the machine. Free flowing debris generally enters the lower moving undercarriage of a tracked machine at the track frame ends when the machine is turning, or between the track rollers due to a sloped surface operation. In one specific example, long exposure to mud can become caked or bricked inside the track roller frame inhibiting the ability of the recoil system to respond to various loads on the track, undermining machine operation and potentially leading to failure. In another example, rocks digested into the track roller frame may lead to fracture or breakage of track components, idlers, rollers and a variety of other components associated with the recoil system. Debris can often build up on the top of a track roller frame by either being carried to the top side of the track shoes and dropped onto the track roller frame top, or by being deposited on top of the track roller frame from track frames submerged in debris. 
     Over the years, engineers have devised a long list of guarding strategies intended to inhibit digestion of debris into the track roller frame of a tracked machine. In fact, guarding strategies date as far back as 1928, where the model Twenty Caterpillar track type tractor included guarding surfaces and skirting intended to inhibit the digestion of debris into its track roller frame assembly. From that time forward, virtually every manufacturer of tracked machines has included some guarding strategy to inhibit digestion of debris into their respective track roller frames. Many of these guard designs are particular to the specific track structure and other machine geometry features that are not easily transferable to different designs. Thus, a guarding strategy for one machine may be totally ineffective and inappropriate for a different machine design. With every new design, new guarding strategies must be devised in order to specifically address the needs and geometry of each new design. 
     The present disclosure is directed toward problems associated with guarding against ingestion of debris into a track roller frame. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, a debris guard assembly for a machine includes a pair of guard plates with a leading edge shaped as an arc of a circle. The pair of guard plates are separated by a distance to flank a track chain. An inboard shield is attached between the plates and defines an idler slot sized for receiving an idler about a same diameter as the circle. 
     In another aspect, a machine includes a pair of idler axle blocks slidably mounted in a track roller frame. An idler is rotatably supported by and between a pair of idler axle blocks. A recoil yoke is attached to the pair of idler blocks. A track that includes track chain is mounted around the track roller frame. A debris guard is attached to at least one of the pair of idler blocks and the recoil yoke. The debris guard includes an inboard shield that defines a slot that receives the idler, and pair of guard plates that flank opposites sides of a segment of the track chain in contact with the idler. 
     In still another aspect, a method of inhibiting debris entry into an interior of a track roller frame includes blocking debris greater than a first size by defining a first clearance slit between an outer width of a track chain and pair of guard plates. Debris greater than a second size is blocked by defining a second clearance slit between an idler and an inboard shield. The first clearance slit and the second clearance slit are arranged in series to define portions of a debris entry pathway from an exterior to an interior of the track roller frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a machine according to one aspect of the present disclosure; 
         FIG. 2  is a diagrammatic view of a track roller frame, idler, debris guard and track according to another aspect of the present disclosure; 
         FIG. 3  is a side view of a track roller frame and idler equipped with a debris guard according to the present disclosure; 
         FIG. 4  is a perspective view of a preassembled unit according to another aspect of the present disclosure; and 
         FIG. 5  is a perspective view of a debris guard assembly according to another aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-5 , a machine  10  according to the present disclosure may be a track type tractor or some other machine that includes a track  13  mounted about a track roller frame  11  and idler  12 . For instance, a variety of track type machines, including but not limited to excavators, loaders and landfill equipment, as well as others, are within the contemplated scope of the present disclosure. Machine  10  includes a variety of features including a debris guard  40  to inhibit entry of debris into track roller frame  11 , which could undermine a recoil system (not shown) or damage other aspects of machine  10 , such as produce excessive wear or breakage of a variety of track roller frame related components. 
     Referring specifically to  FIG. 5 , a debris guard assembly  40  according to the present disclosure may include a pair of guard plates  42  and  43  that are attached on opposite sides of an inboard shield  41 . Guard plates  42  and  43  each include a respective leading edge  50  and  52  that is shaped as an arc of a circle. The pair of guard plates  42  and  43  may be separated by a distance to flank opposite sides of a track chain  15 , such that the track chain  15  is received between the pair of guard plates  42  and  43 , as best shown in  FIG. 2 . This provides a first line of defense by the track chain  15  and the respective guard plates  42  and  43  defining a first clearance slit  65 , also as best shown in  FIG. 2 . In order to provide an adequate thickness to guard plates  42  and  43  without excessive weight, each guard plate may be a composite of thinner plates welded at their periphery with the inner most plate being hollow. Each of the guide plates  42  and  43  may also include a mounting feature, such as an idler axle block mount  51  and  53  as best shown in  FIGS. 4 and 5 . This aspect of the disclosure allows for the guard plates  42  and  43  to move with the idler as it undergoes recoiling events during normal operation to maintain the geometry of clearance slit  65 , even during dynamic movements. The guide plates  42  and  43  may be attached to the inboard shield  41  in any suitable manner such as via a weld seam along an inner surface of the respective guide plates  42  and  43 . 
     Inboard shield  41  includes a top right guard  44 , a top left guard  45  and a rear guard  46  as best shown in  FIG. 5 . Inboard shield  41  defines a slot  47  that surrounds and receives a portion of idler  12  as best shown in  FIG. 2 . In addition, slot  47  terminates in an enlarged opening  48  sized to received a rim  18  of the idler  12 . As best shown in  FIG. 5  (see location of numeral  47 ) and as shown in  FIG. 2 , a segment of idler slot  47  is located between, but separated from, the guard plates  42  and  43 . Together, inboard shield  41  and idler  12  define a second clearance slit  66  that provides a second line of defense against debris entry into the interior of track roller frame  11 . Together, slits  65  and  66  form portions of a serpentine shaped debris entry pathway  67  extending between an exterior and an interior of the track roller frame  11 . Like guard plates  42  and  43 , the inboard shield  41  includes a mount, in particular, a yoke mount  55  that results in the inboard shield also moving with idler  12  during dynamic recoil events to maintain the geometry of clearance slit  66  throughout operation of machine  10 . Although debris guard assembly  40  includes block mounts  51  and  53  as well as a yoke mount  55 , those skilled in the art will appreciate that other attachment strategies could be substituted while remaining within the intended scope of the present disclosure. As best shown in  FIG. 4 , the debris guard  40  may include an orientation alignment feature  57  that interacts with an end  29  of a recoil shaft  28  to prevent the recoil shaft  28  from rotating about its axis. Nevertheless, this feature may be eliminated in the favor of an alternative strategy for inhibiting rotation of shaft  28 , if desired. This aspect of the disclosure is best shown in  FIG. 4 . 
     Referring specifically to  FIG. 3 , the leading edges  50  and  52  of the guard plates  42  and  43  are shaped as an arc of a circle which spans about one quadrant  60 . Nevertheless, those skilled in the art will appreciate that the arcuate span may be selected to suit the particular geometry of any given application. The diameter of the circle corresponding to the leading edges  50  and  52  of guard plates  42  and  43  is about the same as the base diameter of idler  12  so that the leading edges  50  and  52  remain about the same distance away from the underside of shoes  14  as the face of the individual teeth (if any) of idler  12 . In this way, as wear occurs during normal operation of machine  10 , indexing on the idler  12  and wear to track chain  15  can reduce the separation distance between both the rim  18  of idler  12  as well as the leading edges  50  and  52  with respect to the shoes  14 . In other words, providing that wear is not so severe that idler remains out of contact with shoes  14 , the guard plates  42  and  43  will also remain out of contact with shoes  14  during normal intervals of wear that periodically require a belt tensioning adjustment in a known manner. 
     Although not necessary, guard plates  42  and  43  may be parallel to one another and perpendicular to an axis of rotation of idler  12 . Nevertheless, alternative geometry&#39;s, such as an inward slant would also fall within the intended scope of the present disclosure. Although not necessary, the present disclosure contemplates a preassembled unit strategy that better facilitates the debris guard features by allowing them to be assembled as shown in  FIG. 4  prior to installation in track roller frame  11 . In particular, a preassembled unit  20  may include idler  12 , a pair of idler axle blocks  21 , a yoke  22  and debris guard  40  all preassembled as a unit. This preassembled unit is then installed in track roller frame  11  by sliding the idler axle blocks  21  between wear plates until yoke  22  abuts end  29  of recoil shaft  28 . At the same time, the orientation alignment feature  57  engages the outer edges of end  29  of recoil shaft  28  to prevent it from rotating. 
     Those skilled in the art will appreciate that sizing of slot  47  verses the thickness of idler  12  may be selected to shape clearance slit  66  to prevent entry of debris having a size greater than the width of the slit. Likewise, the thickness and spacing of guard plates  42  and  43  along with the width track chain  15  may be selected to prevent entry of debris of size that is different or the same as the width of clearance slit  65 . Although not necessary, the clearance slit  65  may be chosen to be slightly larger than the inner clearance slit  66  due to the fact that more movement in track  13  is generally allowed for normal operation, and larger clearance  65  can prevent contact between guard plates  42  and  43  while preventing a bulk of potential debris from gaining entry into debris pathway  67 . By arranging clearance slits  65  and  66  in series, and by appropriately sizing the same, the serpentine entry pathway  67  can inhibit entry of most undesirable debris without substantially affecting performance of machine  10  generally, or the track system specifically. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure finds potential application to any tracked machine in which their is a desire to inhibit debris from entering a track roller frame that rotationally supports an idler about which a track is mounted. The present disclosure find particular application in track systems that include an idler that is received into the track chain rather than riding on an outer surface of a track chain as in many prior art systems. This strategy allows the debris guard of the present disclosure to interact with the track chain and idler to define a serpentine debris pathway that includes at least two clearance slits in series to present a layered line of defense against entry of undesirable debris into the interior of a track roller frame. The present disclosure finds specific applicability to track type tractors and like machines that operate in hostile environments, including but not limited to mud, rocks, sand and a variety of other debris that could potentially undermine a recoil system or another machine feature if becoming lodged in an undesirable location. 
     The debris guard strategy of the present disclosure also has the advantage of moving with the idler during dynamic recoil events to maintain the geometry of the clearance slits to inhibit ingestion of debris even when the idler is recoiling and moving with regard to other components of machine  10 . By including an arc shape on the guard plates of the debris guard with a diameter about the same as the idler, and with the spacing as taught above, the clearance slit geometry also is maintained during normal wear of the track system. In particular, as the idler becomes more indexed and the track chain  15  wears, the idler rim  18  will tend to ride closer to the underside of the track shoes  14 . As long as this wear does not become excessive, the guard plates  42  and  43  will also remain out of contact with the underside of shoes  14  during normal wear cycles. 
     It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.

Technology Classification (CPC): 1