AU2007200163B2 - Idler for Crawler Track - Google Patents

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention Title: Idler for Crawler Track Applicant: Trackex Pty Ltd The invention is described in the following statement.

-2 IDLER FOR CRAWLER TRACK FIELD OF THE INVENTION The present invention relates to an idler for use with crawler tracks. BACKGROUND TO THE INVENTION 5 Crawler tracks (which are also commonly referred to as "caterpillar tracks") are widely used in vehicles that are used for mining, construction, excavation, agricultural and military purposes. Crawler tracks are typically assembled from track links which are joined together to form a closed loop or chain. The joint between each track link allows relative pivotal movements between the track links. This enables the track to be flexible 10 and maintain its shape. The track links carry track shoes or track plates that form the ground engaging surface of the track. Figure I shows a side view of the track link that is commonly used in crawler tracks. Figure 2 shows an underneath view of the track link shown in figure 1. The track link 10 is typically made from steel. It includes a body 11 having openings 12, 13 that, in 15 use, accept connection pins that allow adjacent track links to be connected to each other. As shown in figure 2, the underneath surface 16 (which, in use, forms an inner surface of the track) includes a central portion 17 and offset end portions 18, 19. In order to assemble a track, a number of track links are positioned as shown in figure 3. The offset end portions 18 and 19 are arranged such that the end portion 18 of 20 one track link overlaps with the corresponding end portion 19 of an adjacent track link. A connecting pin 20 (refer to figure 4) is then inserted through the respective openings 12, 13 in the offset end portions 18, 19 to connect the track links together. The track links are connected together until a complete loop is formed. This loop effectively forms a chain. As shown in figure 4, the chain 21 of connected track links carries track shoes 22. 25 The track shoes 22 engage with the ground when the vehicle is being driven. Figures 5 and 6 show side schematic views of possible arrangements of the tracks. In figure 5, the track 23 (which includes the track links 10 and track shoes 22) is arranged -3 to extend around a drive sprocket 24 and an idler 25. Idler 25 is not a driven wheel and acts to guide the track. Figure 6 shows an alternative track layout for a track on a vehicle. The layout shown in figure 6 is frequently used on larger tracked vehicles. In the embodiment shown 5 in figure 6, the track 23 extends around a drive sprocket 26, a major bogie 27 and an idler 28. It will be appreciated that the tracks shown in figures 5 and 6 may include other components, such as minor bogies, track rollers, carrier rollers and the like. In some tracks, a single loop of track links is used to carry the track shoes. In 10 other tracks, two layers of track links that are spaced apart from each other are used to carry the track shoes. This affords greater strength and stability, particularly where the track is used on a large, heavy vehicle. Interaction between the track links and the idler causes wear of the track links. As the track links move over the idler, the inner surfaces of the track links come into contact 15 with the idler. This contact results in an arcuate wear pattern being formed on the inner surfaces of the track links. This wear decreases the usable service life of the track links and necessitates repair or replacement. United States Patent No. 6,536,853 (which the applicant does not concede forms part of the common general knowledge in Australia) addresses the issue of wear in the 20 lower surface of the track links by providing an idler having a circumferentially extending surface. The circumferentially extending surface has a first notch and a second notch defined therein. The notches on the circumferential part of the idler are sized and positioned such that they contact bushes that are used to connect the track links together. The bushes and the notches in the idler have complementary conformal surfaces that 25 result in the wear on the idler and the track link being significantly reduced. Throughout this specification, the word "comprising" and its grammatical equivalents shall be taken to have an inclusive meaning unless the context indicates otherwise.

4 BRIEF DESCRIPTION OF THE INVENTION In one aspect, the invention resides broadly in a drive train for a track laying vehicle, the drive train including a drive sprocket, an idler and one or more 5 track chains, each of said one or more track chains including a plurality of links pivotally connected to each other and adapted for engagement with said drive sprocket and adapted to wrap around said idler for movement therewith, said idler having a bore or hub for mounting the idler on a shaft for rotation relative thereto about the bore or hub axis and one or more chain supporting faces radially spaced from said bore or hub, .0 the or each chain supporting face comprising a plurality of generally planar link supporting lands together forming a polygonal prismatic face coaxial with the hub axis, the link supporting lands being of substantially equal length in the circumferential direction and the bottom face of adjacent following links being arranged in use to engage adjacent lands of the same chain supporting face. L5 In another aspect, the invention resides broadly in an idler for a track laying vehicle, the idler having a bore or hub for mounting the idler on a shaft for rotation relative thereto about the axis of the bore or hub and one or more chain supporting faces radially spaced from the axis of said bore or hub, each chain t0 supporting face comprising a plurality of generally planar link supporting lands together forming a polygonal prismatic face coaxial with the bore or hub axis, the link supporting lands being of substantially equal length in the circumferential direction and the angle enclosed by adjacent link supporting lands being greater than one hundred and twenty degrees. 25 Preferably, each of the plurality of flat surfaces on the idler have a length that matches the link pitch of the track chain formed by the track links. In some vehicles, the track comprises two chains of track links that support 30 track shoes, the two chains of track links being spaced laterally from each other, the chains of track links passing around the idler as the vehicle moves, the idler comprising a region of larger diameter having a width that allows the region of larger diameter 4a to fit into the space between the two chains of track links and lateral regions located on either side of the region of larger diameter, the lateral regions including a plurality of generally flat surfaces that come into contact with corresponding generally flat surfaces on the track links. 5 An idler in accordance with the invention reduces wear on the track links because the link contacts a flat surface as it passes over the idler. This avoids the scalloping wear patterns on the track links that arise from using conventional idlers. LO In some embodiments, the generally flat surfaces may be provided by wear plates mounted to the idler. The wear plates may be removably mounted to the idler. Appropriate fastening means may be used to removably mount the wear plates to the idler. L5 In some embodiments, the track assembly includes two track chains that are spaced apart from each other.

-5 The present invention also provides a tracked vehicle that includes an idler as described in relation to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS 5 Figure 1 shows a side elevational view of a conventional track link; Figure 2 shows an underneath view of the lower surface or inner surface of the track link shown in figure 1; Figure 3 shows an underneath view of part of a track chain made from joined track links; 10 Figure 4 shows a side elevation view of a track assembly comprising a track chain carrying track shoes; Figure 5 shows a schematic side view of one possible arrangement of a track used on a tracked vehicle; Figure 6 shows a schematic side view of another track assembly for use on a 15 tracked vehicle; Figure 7 shows a perspective view of an idler in accordance with an embodiment of the present invention; Figure 8 shows a side elevation view of the idler shown in figure 7; Figure 9 shows an end elevation view of the idler shown in figure 7; 20 Figure 10 shows a side view of the idler shown in figures 7 to 9 with a track chain passing over the idler; and Figure 11 shows a side perspective view of an idler similar to that shown in Figure 7, but with the generally flat surfaces being formed by removable wear plates.. DETAILED DESCRIPTION OF THE DRAWINGS -6 The drawings have been provided for the purpose of illustrating preferred embodiments of the present invention. Thus, it will be appreciated that the present invention should not be considered to be limited to the embodiments shown in the drawings. 5 Figures 1 to 6 relate to prior art and have been described in the "Background to the Invention" section of this specification. Figures 7 to 9 show various views of an idler in accordance with the present invention. The idler shown in Figures 7 and 9 is intended for use in track assemblies which include two parallel, spaced track claims that carry track shoes. The idler 40 10 shown in figures 7 to 9 includes a hub 42 having an opening 44 therethrough. Opening 44 receives a mounting shaft or axle that enables the idler to be mounted to a track frame or to a vehicle. A rim 46 is connected to the hub. The rim 46 includes a central region 48 that is of larger diameter than the other parts of the rim 46. As can best be seen in figures 7 and 8, central region 48 is generally 15 cylindrical in shape, with a width that is smaller than the width between the two parallel track chains of the track assembly. In this manner, the central region 48 can fit into the space between the parallel track chains as the parallel track chains pass around the idler. This assists in locating and maintaining the track on the idler. The track chains may be fitted with bearings to enable a smooth passage of the track chains over the side walls 50 20 of central region 48. The idler 40 shown in figures 7 to 9 also includes lateral regions 52, 54. Lateral regions 52, 54 preferably do not extend in a radial direction beyond the outer periphery of central region 48, as best shown in figure 8. The lateral regions 52, 54 include a plurality of generally flat surfaces 56. The generally flat surfaces 56 come into contact with the 25 lower surface 16 of the track links in the track chain as the track chain passes around the idler 40. This is shown in figure 10. As the flat lower surfaces 16 of the track links 10 are in contact with the generally flat surfaces 56 of the idler 40, wear on the lower surfaces 16 of track links 10 is significantly reduced. As shown in figure 10, the length of the generally flat surfaces 56 on the lateral 30 regions of the idler 40 equals the pitch of the links in the track chain. This ensures that -7 the links maintain proper contact with the generally flat surfaces 56, as shown in figure 10. It will be appreciated that the idler shown in figures 7 to 10 is intended for use with a track that includes two parallel track chains that are spaced from each other. If a 5 track assembly includes a track that has a single track chain, the outer periphery of the rim of the idler may comprise the plurality of generally flat surfaces. In such embodiments, the central region 48 shown in figures 7 to 9 may be deleted. Figure 11 shows a perspective view of an idler similar to that shown in Figure 7, but with the generally flat surfaces that come into contact with the track during use 10 comprising removable wear plates. The idler 140 shown in figure 11 includes a hub 142 having an opening 144 therethrough. Opening 144 receives a mounting shaft or axle that enables the idler to be mounted to a track frame or to a vehicle. A rim 146 is connected to the hub. The rim 146 includes a central region 148 that is of larger diameter than the other 15 parts of the rim 146. Central region 148 is generally cylindrical in shape, with a width that is smaller than the width between the two parallel track chains of the track assembly. In this manner, the central region 148 can fit into the space between the parallel track chains as the parallel track chains pass around the idler. This assists in locating and maintaining the track on the idler. The track chains may be fitted with bearings to enable 20 a smooth passage of the track chains over the side walls 150 of central region 148. The idler 140 shown in figure 11 also includes lateral regions 152, 154. Lateral regions 152, 154 preferably do not extend in a radial direction beyond the outer periphery of central region 48. The lateral regions 152, 154 include a plurality of generally flat surfaces 156. The generally flat surfaces 156 come into contact with the lower surface of 25 the track links in the track chain as the track chain passes around the idler 140. In the embodiment shown in Figure 11, wear plates 160 are mounted to an underlying surface 162 of the respective lateral regions 154, 156 of the idler 140. As shown in Figure 11, the underlying surfaces 162 may be generally flat. However, it will be understood that the underlying surfaces 162 are not necessarily flat and that the wear 30 plates 160 may be provided with a lower surface that is of complementary shape to the -8 underlying surface 162. For example, if the underlying surface 162 has an arcuate-shaped upper surface, the lower surface of the wear plate may be of complementary arcuate shape such that it closely fits to the underlying surface. The underlying surface 162 is provided with bolt holes 164 which come into 5 register or alignment with bolt holes 166 formed in the wear plate 160. Bolts 168 are passed through the bolt holes 166 and 164 and nuts 172 and washers 170 are used to hold the bolts in place and thereby attach the wear plates to the idler 140. Suitably, the heads of the bolts 168 do not extend above the upper surface of the wear plates 160. This assists in presenting a generally flat surface to the track in passing over the idler. 10 The use of removable wear plates enables worn wear plates to be removed from the idler and replaced with new wear plates. This simplifies refurbishment of worn idlers. The wear plates may be removed whilst the idler is still in place on the machine, thereby reducing the time required to refurbish worn idlers. The wear plates may be available in different thicknesses to accommodate different wear factors on chains or tracks. 15 Those skilled in the art will appreciate that the present invention may be susceptible to variations and modifications other than those specifically described. It will be understood that the present invention encompasses all such variations and modifications that fall within its spirit and scope.

Claims (22)

1. A drive train for a track laying vehicle, the drive train including a drive sprocket, an idler and one or more 5 track chains, each of said one or more track chains including a plurality of links pivotally connected to each other and adapted for engagement with said drive sprocket and adapted to wrap around said idler for movement therewith, said idler having a bore or hub for mounting the idler on a shaft for 0 rotation relative thereto about the bore or hub axis and one or more chain supporting faces radially spaced from said bore or hub, the or each chain supporting face comprising a plurality of generally planar link supporting lands together forming a polygonal prismatic face coaxial with the hub axis, 15 the link supporting lands being of substantially equal length in the circumferential direction and the bottom face of adjacent following links being arranged in use to engage adjacent lands of the same chain supporting face.

2. A drive train according to Claim 1 wherein each link !0 has a bottom contact face of a predetermined length and the length of each link supporting land is about the same as said predetermined length.

3. A drive train according to claim 1, wherein the link supporting lands are of substantially equal width in the axial 25 direction.

4. A drive train according to claim 1, wherein said idler includes a plurality of detachable wear plates and said link supporting lands are formed on said detachable wear plates. 30

5. A drive train according to Claim 1, wherein said one or more track chains comprises two spaced apart chain halves with the corresponding links of said chain halves being aligned laterally and connected by pins and bushes adapted to cTRA09102 -amd 15 June 2009 - 10 engage the drive sprocket and said one or more chain supporting faces comprising two spaced apart chain supporting faces and one of said chain halves is adapted to engage with one chain supporting face and the other of said track chain 5 halves is arranged to engage with the other chain supporting face.

6. A drive train according to Claim 5, wherein said idler has a cylindrical face coaxial with and between said two spaced apart chain supporting faces. 10

7. A drive train according to Claim 6, wherein each of said chain supporting faces is separated from said cylindrical face by a shoulder.

8. A drive train according to Claim 7, wherein each of said chain links has an inside face which is adapted to 15 slidingly engage said shoulder.

9. A drive train according to Claim 8, wherein said cylindrical face is spaced from said bore or hub axis by a distance greater than that of said chain supporting faces.

10. An idler for a track laying vehicle, the idler !0 having a bore or hub for mounting the idler on a shaft for rotation relative thereto about the axis of the bore or hub and one or more chain supporting faces radially spaced from the axis of said bore or hub, each chain supporting face comprising a plurality of generally planar link supporting 25 lands together forming a polygonal prismatic face coaxial with the bore or hub axis, the link supporting lands being of substantially equal length in the circumferential direction and the angle enclosed by adjacent link supporting lands being greater than one hundred and twenty degrees. 30

11. An idler according to Claim 10, wherein said one or more chain supporting faces comprises two spaced apart chain supporting faces one chain supporting face being adapted to engage with one track chain half and the other being adapted cTRA09102 -amd 15 June 2009 - 11 to engage with another track chain half.

12. An idler according to Claim 11, having a cylindrical face coaxial with and between said two spaced apart chain supporting faces. 5

13. An idler according to Claim 12, wherein each of said chain supporting faces is separated from said cylindrical face by a shoulder.

14. An idler according to Claim 13, wherein each of said chain links has an inside face which is adapted to slidingly 0 engage said shoulder.

15. An idler according to Claim 14, wherein said cylindrical face is spaced from said bore or hub axis by a distance greater than that of said chain supporting faces.

16. An idler according to Claim 10 including a plurality 5 of wear plates and wherein said link supporting lands are formed on said wear plates.

17. An idler according to Claim 16 wherein said wear plates are detachably mounted on a rim.

18. An idler according to Claim 17 including keying .0 means between the wear plates and the rim for locating the wear plates relative to the rim.

19. An idler according to Claim 17 wherein said rim includes a plurality of mounting faces corresponding with the number of wear plates against which said wear plates engage. 25

20. An idler according to Claim 19 wherein said mounting faces are adapted to selectively receive sets of wear plates of different thickness.

21. A drive train incorporating an idler as hereinbefore described with reference to Figs. 7 to 11. 30

22. An idler as hereinbefore described with reference to Figs. 7 to 11. cTRA09102 -amd 15 June 2009