Patent Application
20070247002
This invention relates generally to endless track drive systems and, more specifically, to methods for constructing drive and traction wheels for rubber track skid steer vehicles.
Small skid steer vehicles 10, such as that shown in
In prior systems, the chemical bond between the polystyrene-butadiene and the hub was essential because of the manner of securing wheels to shafts in the endless track system. As shown in
The rims 24 of the sections 22a, 22b are much more prone to separate from the hubs 26 inasmuch as the elasticity of the rims 24 does not maintain them in place as would a rim formed as a complete circle. A strong chemical bond between the rims 24 and hubs 26 is therefore important in prior wheels to avoid separation. Even in applications with a rim formed in a complete circle, durability issues remain. The rubber compounds commonly used do not wear well when subjected to the harsh environments encountered by the tracked vehicles. The rim constantly rolls against the track with rocks, dirt, sand, vegetation, and other debris grinding between it and the track.
In view of the foregoing, it would be an advancement in the art to provide a rim 24 formed of much more durable material secured to a UHMW hub with decreased risk of separation.
A wheel includes a hub bearing a plurality of projections extending radially outwardly and having a proximal portion secured to the hub and a distal portion forming an outermost portion of the hub. The distal portions are substantially larger in the circumferential direction than the proximal portion. A rim is molded around the plurality of projections in order to retain the rim. The projections extend substantially entirely across the hub substantially parallel to the axis of symmetry. The space between the projections may have various shapes including a dove tail shape and a tear drop shape. In some embodiments, the plurality of projections further include a groove extending into the plurality of projections parallel to the axis of symmetry. In some embodiments, the hub is formed of UHMW and the rim is formed of polyurethane.
The wheel may be used in an endless track drive system including a track supported by multiple shafts bearing drive wheels and traction wheels. The shafts bear outer flanges integrally secured proximate first and second ends of the shaft and a middle flange integrally secured to the shaft between the first and second outer flanges. The wheel secures to the middle flange and engages the track. In one embodiment, the wheel is formed of first and second semi-circular sections, the first and second sections are combinable to form a complete wheel that may be secured to a flange in a mid-portion of an axle.
A method of forming a wheel for an endless track system is also disclosed. First and second hub sections are formed. The sections are combinable to form a circular wheel. A plurality of projections extends radially outward from the hub sections. The projections have outermost portions larger than proximal portions. Rim sections are molded onto the projections. The hub sections are mounted to a flange.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
Referring to
Other mounting systems are also possible, for example, the wheel 20 may mount directly to the shaft 16 by means of set screws or the like. The shaft 16 may also be splined to constrain the wheel 20 to rotate with the shaft 16. The sections 22a, 22b may also have various embodiments. For example, the sections 22a, 22b may be of unequal sizes. One section 22a, 22b may be no larger than necessary to enable a shaft 16 to insert into the other section 22a, 22b.
Referring to
Referring to
Materials used for the rim 24 may include polyurethane or like polymers. The hub 26 may therefore also be formed of any material offering sufficient structural strength including ultra-high molecular weight (UHMW) polymers, other rigid polymers, and metals. The materials used need not be limited to those capable of chemically bonding with one another. However, in some embodiments, a chemical bond may be encouraged by using carbon black in both hub polymer and rim polymer.
It is apparent that the novel wheel disclosed herein enables the use of a wider range of materials than is possible in prior wheels. Wheels constructed in the novel manner described above have been shown to have a useful life 55 times longer than prior wheels. The benefits of the novel wheel disclosed is not limited to wheels formed in sections, but rather may be used to increase the useful life of both traction and drive wheels secured to any of the flanges 18a-18c of a shaft 16, or to another component of an endless track drive system.
While the preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
