Isolated center tread rim idler wheel

An isolated center tread rim idler is disclosed. The isolated center tread rim idler includes an idler body, and a circular rim including a radially outer portion configured to engage track bushings of a track assembly. The circular rim also includes a radially inner portion of less width than the radially outer portion. The radially inner portion is configured to cooperate with an outer circumferential surface of the idler body. The circular rim includes a curved transition portion between the radially outer portion and the radially inner portion. A resilient ring engages the curved transition portion. A side plate is fastened to a side of the idler body, and the side plate includes a portion engaging the resilient ring.

TECHNICAL FIELD

The present disclosure relates generally to an idler and, more particularly, to an isolated center tread rim idler.

BACKGROUND

Earthmoving equipment and construction machines such as, for example, hydraulic excavators and track-type tractors, are used to perform a variety of tasks, typically in rugged environments. In order to enable machine movement, one or more track mechanisms may be provided on such machines. Conventional track mechanisms may include a drive sprocket and one or more idlers to support and enable movement of a ground engaging track about the drive sprocket and idler(s). A track idler may rotate about an axis, and may include a rim portion that engages a plurality of track link members that are interconnected by spaced track pins. Some idlers, for example center tread idlers, engage bushings extending between the laterally spaced links of a track mechanism. The drive sprocket, in combination with the engagement between the idler rim and the track bushing, provides the force that moves the machine. However, contact between the idler rim and the track bushings generate noise and vibrations that are detrimental to both the machine and its operator.

To help dampen the vibration and noise created by metal-on-metal contact in track assemblies and idler wheels, isolation devices, such as, for example, rubber inserts, have been used. U.S. Pat. No. 3,127,211 (the '211 patent) issued to Kordes et al. on Mar. 31, 1964, discloses a wheel assembly that employs an elastic member placed between a rim and a wheel body. In particular, the '211 patent describes a rail vehicle wheel with an elastically supported rim in which two annular elastic inserts may be provided between the wheel body and the rim.

Although the rail vehicle wheel of the '211 patent may provide some damping of vibration and noise by employing elastic inserts, the arrangement in the '211 patent may have limitations. For example, forces exerted by the rim on the elastic inserts may be so great as to repeatedly compress the elastic inserts beyond their elastic limit. This may lead to early failure of the elastic inserts. Also, the arrangement of the rim relative to the elastic inserts and the wheel body may cause the elastic inserts of the '211 patent to potentially experience both tension and compression and incur destructive shear forces under side loading. In addition, assembly of the wheel of the '211 patent may be problematic. The shape and relationship of components in the '211 patent may render it difficult to property seat both annular elastic inserts during assembly.

SUMMARY

In one aspect, the present disclosure is directed to an isolated center tread rim idler. The isolated center tread rim idler may include an idler body and a circular rim including a radially outer portion configured to engage track bushings of a track assembly. The circular rim may include a radially inner portion of less width than the radially outer portion, and the radially inner portion may be configured to cooperate with an outer circumferential surface of the idler body. The rim may include a curved transition portion between the radially outer portion and the radially inner portion, and a resilient ring may engage the curved transition portion. A side plate may be fastened to a side of the idler body, and the side plate may include a portion engaging the resilient ring.

In another aspect, the present disclosure is directed to a method of assembling an isolated center tread rim idler. The method may include mounting a first resilient ring on a portion of a first side plate, positioning an idler body adjacent the first side plate, and positioning a circular rim adjacent an outer circumferential surface of the idler body with a first transition portion of the rim in contact with the first resilient ring. The method may also include positioning a second resilient ring in contact with both the circular rim and a portion of a second side plate, and fastening the first and second side plates to the idler body.

DETAILED DESCRIPTION

FIG. 1is a partial view of a mobile machine10, including a portion of a track assembly12associated with the mobile machine. Mobile machine10may be any of various mobile machines that employ track assemblies for ground transportation and/or for mobility during machine operation. For example, mobile machine10may be a track-type tractor, a tracked loader, a hydraulic excavator, or any other mobile machine. Track assembly12may include an idler assembly14, cooperating with track16of track assembly12. While only a portion of track assembly12is illustrated inFIG. 1, it will be understood that, in addition to idler assembly14, a drive sprocket (not shown) and one or more other idler assemblies (also not shown), and other generally conventional track assembly components, may be associated with track assembly12. Track16may include a plurality of links18connected by transverse track pins20and forming an endless loop about idler assembly14, the drive sprocket (not shown), and any other idler assemblies that may be associated with the track assembly. Idler assembly14may include an outer peripheral surface22configured to engage track bushings24that may be associated with track pins20.

FIG. 2illustrates a perspective cut-away view of a portion of idler assembly14. Idler assembly14may include a circular idler body26, and idler body26may include a hub portion28configured to be positioned about an axle for rotation. In the embodiment illustrated inFIG. 2, idler body26may include an enlarged hub portion28integral with a central flange30. A peripheral portion32of reduced thickness relative to central flange30may be included adjacent the outer circumference of idler body26. Peripheral portion32may include a plurality of apertures34extending through its thickness. Idler body26may include an outer circumferential surface36at the outer diameter of the idler body. Idler body26may be a cast component made from a material of suitable strength and durability commensurate with the intended operating environment such as, for example, a suitable ferrous alloy material.

Idler assembly14also may include a circular rim38. Circular rim38may be an annular member having an inner circumferential surface40at its inner diameter. As can be seen in the more detailed view inFIG. 3, the inner circumferential surface40may be spaced from the outer circumferential surface36of idler body26by a radial gap41. As can be seen by reference toFIGS. 2 and 3, circular rim38may be T-shaped in cross-section, including a wider radially outer portion42and a radially inner portion44that is narrower than radially outer portion42. For example, in one embodiment, radially outer portion42may be approximately three times the width of radially inner portion44. Circular rim38may include a curved transition portion43on one side of circular rim38between radially outer portion42and radially inner portion44, and a curved transition portion45on the other side of circular rim38between radially outer portion42and radially inner portion44. Circular rim38may include the outer peripheral surface22at its outer diameter that is configured to engage track bushings24associated with track pins20. Circular rim38may be a cast component, for example, made from a material of suitable strength and durability commensurate with the intended operating environment. For example, circular rim38may be a suitable ferrous alloy material.

Idler assembly14may include side plates46,48, positioned adjacent idler body26and circular rim38. Side plates46,48each may be annular members overlapping the radial gap41between circular rim38and idler body26. Referring to first side plate46, for example, it may include a wider projecting portion50and a narrower planar portion52. Second side plate48may be similar to first side plate46, and may include wider projecting portion54and narrower planar portion56. Side plates46,48may be fastened to opposite sides of idler flange26by suitable fasteners. For example, side plates46,48may be bolted to peripheral portion32by a plurality of bolts58extending through apertures60in side plates46,48and apertures34extending through the thickness of peripheral portion32. Wider projecting portions50,54of side plates46,48may be spaced from lateral surfaces of radially inner portion44of circular rim38by lateral gaps62and64.

Annular resilient rings66,68may be situated between circular rim38and side plates46,48. Referring toFIG. 3, for example, resilient ring66may engage curved transition portion43of circular rim38, and may engage ledge portion70of side plate46. Similarly, resilient ring68may engage curved transition portion45of circular rim38, and may engage ledge portion72of side plate48. Resilient rings66,68may be O-rings, for example, having circular cross-sectional shapes. However, resilient rings66,68may be of cross-sectional shape other than circular, such as oval, for example. As can be seen inFIG. 3, for example, resilient rings66,68may be somewhat compressed in the assembled idler, exhibiting a cross-sectional shape different from that in an unassembled state. Resilient rings66,68may include various resilient materials, such as, for example, natural rubber, neoprene rubber, butyl rubber, etc. The diameter and/or cross-sectional area of resilient rings66,68may vary based on idler assembly parameters, expected forces to be encountered during machine operation, etc.

Referring toFIG. 3, for example, circular rim38may exert forces against resilient rings66,68via curved transition portions43,45during machine operation as track16moves about idler assembly14. Such forces may compress resilient rings66,68against ledge portions70,72of side plates46,48. A distance x may exist between radially outer portion42of circular rim38and ledge portions70,72of side plates46,48. This distance x may be substantially equivalent to a cross-sectional diameter of resilient rings66,68in a normal engagement state of track16against idler assembly14, and gap41may then be a distance y. The ratio x/y may be selected to permit a degree of compression of resilient rings66,68responsive to external forces on track16without permitting contact between outer circumferential surface36of idler body26and inner circumferential surface40of circular rim38(i.e., without closing gap41). As a result, external forces exerted on track16may be absorbed and/or attenuated by resilient rings66,68without metal-on-metal contact between outer circumferential surface40of circular rim38and inner circumferential surface36of idler body26. However, while selected to permit a certain degree of compression of resilient rings66,68, ratio x/y also may be selected to permit contact between inner circumferential surface36and outer circumferential surface40before resilient rings66,68can be compressed to a degree that may exceed the elastic limit of the resilient material of resilient rings66,68.

Continuing to refer toFIG. 3, resilient rings66,68may be so situated between curved transition portions43,45of circular rim38and ledge portions70,72of side plates46,48as to reduce and/or substantially preclude shear forces on resilient rings66,68even in the event of side loading on circular rim38. While external forces on circular rim38may ordinarily tend to be exerted generally along the direction of arrow F1, external conditions, such as rugged terrain, may cause substantial side loading on circular rim38, for example along the direction of arrow F2or arrow F3. As can be seen inFIG. 3, a force along the direction of arrow F2may tend to exert compression on resilient ring68, and lateral gap64may close with contact between the lateral surface of radially inner portion44and side plate48before any substantial shear forces can be exerted on resilient ring66. Similarly, a force along the direction of arrow F3will tend to exert compression on resilient ring66, and lateral gap62may close with contact between the lateral surface of radially inner portion44and side plate46before any substantial shear forces can be exerted on resilient ring68. Lateral gaps62,64may be so selected as to preclude compressive or shear forces on resilient rings66,68that may exceed the elastic limit of the resilient material of the resilient rings.

Radial gap41(i.e., distance y) and lateral gaps62,64may be selected based on the elastic properties of the resilient rings66,68, forces that may be expected on idler assembly14during machine operation, and idler and resilient ring sizes. For example, a typical radial gap41may be substantially within the range from 1-5 mm, for example 1.0 mm. A typical lateral gap62,64may be substantially within the range from 0.5-2 mm, for example 0.5 mm. Typically, radial gap41will be greater than lateral gaps62,64, and distance x typically will be substantially larger than radial gap41(distance y). While the cross-sectional diameter of resilient rings66,68may be substantially larger than radial gap41, outer circumferential surface36and inner circumferential surface40may contact, closing radial gap41before compressive forces, for example exerted along the direction F1, can distort resilient rings66,68beyond their elastic limit.

INDUSTRIAL APPLICABILITY

In general, an isolated center tread rim idler may be applicable to any mobile machine that is moved using a track mechanism with an idler. For example, in a track-type tractor or other tracked machine, a driven track may include one or more of the disclosed isolated center tread rim idlers to at least partially absorb the vibrations, shocks, and/or noise generated during machine movement over rough terrain. The presence of the resilient rings and the gaps may serve to prevent metal-to-metal contact between the circular rim and the idler body, and/or between circular rim and side plates. However, the gaps may be selected to ensure that metal-to-metal contact occurs before the resilient rings may be compressed an amount sufficient to exceed the elastic limit of the material within the resilient rings. The resilient rings may further serve to substantially seal the space between the circular rim and the side plates and preclude the entry of contaminants into the gaps.

The isolated center tread rim idler may be assembled on a suitable work surface, for example a fixture or jig sized and shaped to accommodate components of the idler. Initially, referring to step101inFIG. 4, and referring toFIGS. 2 and 3to better visualize the various components of the idler assembly, a first resilient ring, for example an o-ring, may be mounted on a first side plate. For example, the first side plate may be placed on a work surface, or on a suitable jig, with a ledge portion of the first side plate readily accessible. The first resilient ring may be positioned on the ledge portion of the side plate. For example, the resilient ring may be stretched slightly and seated against the contoured surface of the ledge portion. Thus the resilient ring may be properly associated with the side plate and mounted on the ledge portion of the side plate with facility and without special tools.

After the first resilient ring is assembled on the first side plate, a circular idler body may be positioned adjacent the first side plate, referring to step102ofFIG. 4. At this point it also may be convenient to place bolts within the respective apertures of the side plate and the idler body. For example, bolts may be positioned with their heads against the work surface, projecting through the side plate and the idler body. Alternatively, bolts may be inserted later in the assembly process.

Once the idler body is in place relative to the first side plate, and referring to step103inFIG. 4, a circular rim may be positioned adjacent the outer circumferential surface of idler body with a first curved transition portion of the circular rim in contact with the first resilient ring. The ring shape of circular rim has an internal diameter that is larger than the external diameter of the circular idler body in order to establish a gap (FIG. 3). Accordingly, positioning of the circular rim relative to the idler body may be accomplished with facility and without special tools. As the rim is positioned relative to the idler body, the first curved transition portion of rim may engage the first resilient ring.

With the circular rim in place relative to the idler body and the first resilient ring, a second resilient ring may be positioned relative to a second curved transition portion of the circular rim, step104, and a second side plate may then be positioned adjacent the idler body and in contact with the second resilient ring, step105. Alternatively, the second resilient ring may first be positioned on a second side plate, step106, for example by slightly stretching the resilient ring and seating it against the contoured surface of a ledge portion of the second side plate. Where the second resilient ring is first positioned on the second side plate, the assembled second side plate and second resilient ring may then be positioned adjacent the idler body with the second resilient ring in contact with the second curved transition portion of the circular rim, step107.

Once both resilient rings, the circular rim, and both side plates are positioned relative to the idler body, the first and second side plates may be fastened to the idler body, step108. For example, the first and second side plates may be secured to the idler body by the plurality of bolts. Where the bolts have first been positioned relative to the first side plate and the idler body, positioning of the second side plate in step105or step107may include positioning the second side plate with its apertures aligned with and positioned over the extending threaded portion of the bolts. Final assembly of the idler wheel may be completed by placing nuts over the bolts. In final assembly, the resilient rings contact both the circular rim and the side plates with a degree of compression sufficient to substantially preclude entry of external contaminants into gaps in the idler assembly.

The T-shaped cross-section of the circular rim with its curved transition portions between the wider radially outer portion and narrower radially inner portion, and the ledge portions of side plates, combine to provide contoured surfaces that both facilitate assembly of the idler assembly and ensure that shear forces acting on the resilient rings are minimized. Assembly of the idler body, the circular rim, the side plates, and the resilient rings may be accomplished with a minimum of tools. For example, where the side plates are fastened to the idler body by a plurality of bolts, it is possible that the only assembly tool may be an appropriate tool to secure the bolts, e.g., a wrench.

Employing resilient rings between the rim and the side plates secured to the idler body enables a reduction in the transmission of both sound and vibration between the rim and the idler body. The resilient rings combined with controlled radial and lateral gaps between the rim and the idler body prevent metal-on-metal contact between the rim and the idler body during normal machine operation. Because the resilient rings essentially receive only compressive forces, they are not subjected to destructive shear stresses. Since the gap between the rim and the idler body serve as control gaps set to limit compression of the resilient rings to less than that which would exceed their elastic limit, the rings may not be crushed and/or unduly distorted, and the life of the resilient rings may be extended. Additionally, the contact of the resilient rings with the curved transition portions and with the ledge portions of the side plates serves to provide a seal to substantially preclude entry of contaminants, e.g., dirt, grit, etc., that may fill the radial gap and/or lateral gaps.