Sprocketed idler for a track assembly

Wheel substitutes for land vehicles – Tracks or treads – With guide means for interfitting with sprocket wheel or roller

Reexamination Certificate

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Details

C305S123000, C305S199000

Reexamination Certificate

active

06250726

ABSTRACT:

TECHNICAL FIELD
This invention relates to track assemblies for a track-type machine and more particularly to a track assembly utilizing roller bushings and sprocketed idlers.
BACKGROUND ART
Conventional track assemblies utilized on track-type machines have typically consisted of a pair of parallel track chains comprised of a plurality of link members that are interconnected by laterally disposed track pins. A track bushing is commonly disposed about the pin and is secured to the links. The bushing is adapted to engage a drive sprocket that propels the track assembly about a track roller frame and ultimately provides the tractive force necessary to power the machine. In recent times and for certain applications, the bushing has taken the form of a “roller” bushing and is not fixed to the links but rather is allowed to rotate about the pin relative to both the pin and the links. This design reduces the wear between the drive sprocket and the bushings which has been known to be quite severe, especially in the abrasive conditions in which track-type machines commonly operate.
Another source of wear occurs on the link members of the track chain. The link members commonly have a wear rail defined on an inwardly directed surface that engages the wear surfaces on the guide rollers and the idlers mounted to the track roller frame. As the track assembly rotates about the track frame, the wear rails of the links are continually brought into contact with the wear surfaces and are thus subjected to severe wear. This is especially critical at the interface between the idlers and the wear rails of the links. Conventional idlers are relatively large diameter wheels that have a pair of laterally extending wear surfaces, or treads, which are positioned to contact the wear rails of the links. An idler is further identified as a non-driving wheel that is positioned between the treads and which runs between the links to act as lateral guides for the track chains at one or more ends of a track assembly. The track assembly may have a single idler in the case of a generally oval track or there may be a pair of idlers in the case of a triangular track configuration. As the generally planar surface of the wear rails is continually brought into contact with the circular idler wheel or wheels of conventional idlers, an arcuate surface begins to form on the wear rails. This wear, of course, is accelerated in more abrasive soils. When this type of wear occurs, the arcuate wear surface will create a highly uneven “platform” or “scallop” for the machine as the track chain lays on the ground and the guide rollers roll across the guide rails. This results in an extremely rough ride due to vibration which is not only uncomfortable for the operator of the machine, it is also structurally fatiguing to tractor components. Additionally, the noise of the metal on metal contact of the idlers striking the guide rails is often unpleasant and fatiguing to the machine operator.
The present invention is directed to overcoming one or more of the problems set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a track assembly includes a chain assembly defined by a plurality of link members connected together to form a pair of parallel continuous track chains. The track chains are connected by a plurality of laterally extending pin members, each pin member having a bushing member mounted for relative rotation about the pin member. The track assembly also has a roller frame assembly having first and second end portions. A first idler having a plurality of teeth is mounted for rotation on the first end portion. The roller frame also has a second idler mounted for rotation on the second end portion. The second idler likewise has a plurality of teeth. The teeth of the first and second idlers are adapted to engage the roller bushings, which engagement entrains the chain assembly about the roller frame.
In another aspect of the present invention, a track assembly includes a roller frame assembly having first and second end portions with a first track chain defining a plurality of link members and a second track chain defining another plurality of link members, the second track chain being positioned adjacent the first track chain in a spaced, parallel relation. A plurality of pin members extends laterally between the link members of the respective track chains to connect the first and second track chains to one another. Also, a roller bushing is rotatably disposed about each of the pin members, the roller bushings being mounted for relative rotation with respect to the pin members. The first idler has teeth and is mounted on one of the end portions of the roller frame assembly. The teeth are adapted for engagement with the roller bushings to guide the track chains in relative movement with respect to the roller frame assembly. Additionally, the roller frame has a second idler having teeth. The second idler is mounted on another one of the first and second end portions of the roller frame assembly. The teeth of the second idler are likewise adapted for engagement with the roller bushings to guide the track chains for relative movement with respect to the roller frame assembly. The roller frame also has a drive wheel having teeth, but this drive wheel is mounted on a machine frame between the first and second idlers. It is likewise adapted for engagement with the roller bushings to guide the track chains for relative movement with respect to the roller frame assembly.
In yet another aspect of the present invention, a track assembly includes a chain assembly defined by a plurality of link members connected together to form a pair of parallel continuous track chains. The track chains are connected by a plurality of laterally extending pin members, each pin member having a bushing member mounted for relative rotation about the pin member. The track assembly also has a roller frame assembly having first and second end portions. A first idler having a plurality of teeth is mounted for rotation on a selected one of the end portions. The teeth of the first idler are adapted to engage the roller bushings, which engagement entrains the chain assembly about the roller frame.
With a track assembly having one or more idlers as set forth above, the contact between the wear rail surface of the track link members and the idlers is substantially eliminated. Because the guiding contact occurs between the rounded surface of the idler and the rounded surface of the bushing, the integrity of the substantially planar surface of the wear rail is maintained. Ultimately, this results in a relatively smooth interface between the guide rollers of a track assembly and the track chain, and therefore an improved ride for the machine. It also reduces the transmission of vibration and rhythmic forces into the surrounding frames and related structure which is known to be deleterious to the life of these structures. Additionally, recent testing with roller bushings combined with sprocketed idlers has been shown to improve the wear life of link members over 20 percent and to reduce track assembly noise level by approximately two decibels.


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