Patent Description:
Continuous track, also called tank tread or caterpillar track, is a system of vehicle propulsion in which a continuous band of treads (e.g., track pads, track links, etc.) is driven by two or more wheels and/or sprockets. The band may be made of modular plates or pads. The large surface area of the tracks distributes the weight of the vehicle better than steel or rubber tires on an equivalent vehicle, enabling a continuous tracked vehicle to traverse soft ground with less likelihood of becoming stuck due to sinking. In the case of heavy equipment, track pads of the band may be subject to significant wear from contact with rollers and/or a sprocket that drives the band.

One attempt to mitigate wear with regard to a track link is disclosed in International Application Publication No. <CIT> ("the '<NUM> application"). In particular, the '<NUM> application discloses a track link comprising a body part and a guidance horn wherein the body part and the guidance horn are integral with each other and are made of light alloy and at least one of the body part and the guidance horn have embedded in the light alloy thereof a discrete ceramic material.

While the track link of the '<NUM> application may disclose a track link having a guidance horn with a discrete ceramic material embedded in the light alloy thereof, the '<NUM> does not provide wear resistance or increased toughness for a sprocket-engaging surface or a roller-engaging surface of the track link. Furthermore, the track link of the '<NUM> application may be formed of a light alloy, which may not provide adequate bearing strength or toughness for some applications.

The multi-material track pad of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.

The present disclosure is related to a track pad for a continuous track assembly, comprising a body formed of a first material with a first hardness; at least one roller-engaging surface configured to engage a roller of the continuous track assembly, wherein the roller-engaging surface is formed of a second, different, material with a second hardness that is greater than the first hardness, and wherein the second material is configured to engage the roller; and characterised by the provision of two roller-engaging surfaces and two sprocket-engaging surfaces, wherein a first sprocket-engaging surface configured to engage a sprocket when operated in a first direction and a second sprocket-engaging surface configured to engage a sprocket when operated in a second direction, said first and second sprocket-engaging surfaces being formed of the second material. The track pad further comprises one or more bushings configured to link the track pad to another track pad, wherein the one or more bushings are located in the body by suspending or placing them in a casting mold used for the casting of the track pad at the time of manufacture and are formed of the second material; and wherein the first material is a metal material and the second material is a ceramic material.

This disclosure relates to a track pad. The track pad has universal applicability to any machine utilizing such a track pad in a continuous track assembly. The term "machine" may refer to any machine that has a continuous track assembly, such as heavy machinery and/or the like.

<FIG> is a diagram of an example track pad <NUM>. As shown, the track pad <NUM> includes a body <NUM>, a ground-engaging surface <NUM>, one or more roller-engaging surfaces <NUM>, one or more sprocket-engaging surfaces <NUM>, and/or one or more bushings <NUM>. The track pad <NUM> may be part of a continuous track assembly, sometimes referred to as a track chain. For example, the continuous track assembly may be composed of multiple track pads <NUM> linked together, as described in more detail in connection with <FIG>, below.

In some implementations, the body <NUM> is formed of a metal material, e.g. steel. The body is formed using a metal casting process, such as permanent mold casting. In permanent mold casting, a casting material (e.g., steel) is poured into a mold and cooled to form the body <NUM>. The material used to form the body <NUM> may be associated with a hardness that is less than a hardness of materials used for a roller-engaging surface <NUM>, a sprocket-engaging surface <NUM>, and/or a bushing <NUM>. As a non-limiting example, the material used to form the body <NUM> may have a hardness of approximately <NUM> HRC. This may provide resistance to cracking or other deformation to which the body <NUM> may be vulnerable.

As further shown, the body <NUM> may be associated with a ground-engaging surface <NUM>. In some implementations, the ground-engaging surface <NUM> may be a same material as the body <NUM>. For example, the ground-engaging surface <NUM> may be part of the body <NUM>. In some implementations, the ground-engaging surface <NUM> may be attached to the body <NUM>. For example, the ground-engaging surface <NUM> may be a detachable shoe, and/or the like, that can be replaced when desired. In some implementations, the ground-engaging surface <NUM> may be formed of steel or a similar material. In some implementations, the ground-engaging surface <NUM> may be formed of a different material than the body <NUM>.

The roller-engaging surfaces <NUM> and the sprocket-engaging surfaces <NUM> are shown with diamond hatching in <FIG>. The diamond hatching indicates that the roller-engaging surfaces <NUM> and the sprocket-engaging surfaces <NUM> are formed of a different material than the body <NUM> (e.g., and/or the ground-engaging surface <NUM>). The bushings <NUM> are formed of a different material than the body <NUM>. The roller-engaging surfaces <NUM>, the sprocket-engaging surfaces <NUM>, and the bushings <NUM> are formed of a ceramic material with a higher hardness than the body <NUM>.

In some implementations, the roller-engaging surfaces <NUM>, the sprocket-engaging surfaces <NUM>, and/or the bushings <NUM> may be associated with a melting point that is higher than a melting point of the body <NUM>. This may allow for forming of the body <NUM>, with the roller-engaging surfaces <NUM>, the sprocket-engaging surfaces <NUM>, and/or the bushings <NUM>, using metal casting techniques, as described in more detail below.

The track pad <NUM> is formed using a metal casting technique. For example, the roller-engaging surfaces <NUM>, the sprocket-engaging surfaces <NUM>, and/or the bushings <NUM> may be suspended in a mold for the track pad <NUM>. The bushings <NUM> are placed in the mold. For example, the roller-engaging surfaces <NUM> may be placed on a bottom surface of the mold and the sprocket-engaging surfaces <NUM> may be placed on surfaces of the mold corresponding to the sprocket-engaging surfaces <NUM>. Molten steel may be poured into the mold to form the track pad <NUM>. As a result of being suspended or placed in the mold, the roller-engaging surfaces, the sprocket-engaging surfaces, and/or the bushings <NUM> may be mated with the track pad <NUM>.

In some implementations, a roller-engaging surface <NUM> or sprocket-engaging surface <NUM> may be at least partially embedded in the track pad <NUM>. In some implementations, the roller-engaging surface <NUM> may be one of a plurality of roller-engaging surfaces <NUM> that are substantially parallel to each other. In some implementations, the roller-engaging surface <NUM> or sprocket-engaging surface <NUM> may be provided on a surface of the track pad <NUM>. In some implementations, a face of the roller-engaging surface <NUM> or sprocket-engaging surface <NUM> (e.g., an inward-facing face with reference to <FIG>) may have one or more features to cause the roller-engaging surface <NUM> or sprocket-engaging surface <NUM> to reliably mate with the track pad <NUM> (e.g., grooves, scores, etc.). In some implementations, the roller-engaging surfaces <NUM> may collectively cover substantially all of a contact area between a roller (e.g., roller <NUM> of <FIG>) and the track pad <NUM>.

In some implementations, the roller-engaging surface <NUM> may be substantially flat. For example, the roller-engaging surface <NUM> may be provided on a surface that a roller (e.g., roller <NUM> of <FIG>) may engage during operation of a machine. In some implementations, the sprocket-engaging surface <NUM> may be a curved surface. In some implementations, the sprocket-engaging surface <NUM> may be substantially flat. In some implementations, the sprocket-engaging surface <NUM> may include a groove, a cup, and/or the like, configured to engage a sprocket (not shown). In some implementations, the sprocket-engaging surface <NUM> may be configured to engage a sprocket (not shown).

In some implementations, a bushing <NUM> may have an annular base (e.g., of a cylindrical shell of the bushing <NUM>) that is exposed, as shown in <FIG>. For example, the annular base may be flush with a surface of the track pad <NUM>, or may be offset from the surface of the track pad <NUM>. In some implementations, the annular base of the bushing <NUM> may be covered by the track pad <NUM>. For example, a steel surface may wrap around the side of the bushing <NUM> to cover the annular base.

Other examples are possible and may differ from what was described in connection with <FIG>.

<FIG> is a diagram of a top view of the example track pad <NUM>. As shown, the track pad <NUM> includes two roller-engaging surfaces <NUM> and two sprocket-engaging surfaces <NUM>. A first sprocket-engaging surface <NUM> engages the sprocket (not shown) when the sprocket operates in a first (e.g., forward) direction, and a second sprocket-engaging surface <NUM> engages the sprocket when the sprocket operates in a second (e.g., reverse) direction. Bushings <NUM> are not shown in <FIG> for simplicity.

A roller (e.g., roller <NUM>, shown in <FIG>) engages the roller-engaging surfaces <NUM>. In some implementations, the roller may include a guide element to guide the track pad <NUM> in motion. For example, the guide element (shown in <FIG>) may be provided in the slot <NUM> (which is also shown in <FIG>).

Multiple track pads <NUM> may be connected to each other to form a track chain or continuous track. For example, the protrusion <NUM> may fit into the slot <NUM>. The bushings <NUM> may be provided in respective protrusions <NUM>. A pin or similar element may be inserted through the bushings <NUM> (not shown in <FIG>) to link adjacent track pads <NUM>.

<FIG> is a diagram of the track pad <NUM> engaging with a roller <NUM>. As shown by reference number <NUM>, the roller <NUM> engages the roller-engaging surfaces (e.g., roller-engaging surfaces <NUM> of <FIG> and <FIG>). As further shown, a guide element <NUM> may extend into a slot (e.g., slot <NUM> of <FIG>), and may be configured to guide the track pad <NUM> during operation of a machine. For example, the slot may be configured to receive the guide element <NUM> when the roller <NUM> engages the roller-engaging surfaces. As shown, the guide element <NUM> may not engage a top surface of the track pad <NUM>.

The track pad <NUM> described herein may improve expected service life of track pads of continuous track assemblies. By way of example only, an expected service life of a track pad may be extended two-fold (or more) in comparison to some techniques for hardening surfaces, such as induction-based hardening. For example, the increased hardness of the roller-engaging surfaces <NUM>, sprocket-engaging surfaces <NUM>, and/or bushings <NUM> may provide improved bearing strength and resistance to friction-based wear in comparison to induction-based hardening, thus improving service life.

The technique of suspending or placing the bushings <NUM> in the casting mold may increase an upper limit of hardness for the bushings <NUM>. For example, one technique for placing bushings in a track pad is the interference fitting technique, wherein a bushing is compressed to fill the opening and secure the bushing. However, the interference fitting technique may limit the hardness of materials that can be used for the bushings, since interference fitting may cause cracking of sufficiently hard materials. By suspending or placing the bushings <NUM> in the casting mold for casting of the track pad <NUM>, a harder material may be used for the bushings <NUM>, thereby improving service life and wear resistance of the bushings <NUM>.

In some implementations, the roller-engaging surfaces <NUM> and/or the sprocket-engaging surfaces <NUM> may be embedded in the track pad <NUM>. This may prevent contaminants from entering between the surfaces and the track pad <NUM>. In some implementations, an annular base of the bushing <NUM> may be enclosed by the body <NUM>. This may also prevent contaminants from entering between the bushing <NUM> and the body <NUM>, thereby increasing the expected service life of the bushing <NUM>.

As used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more. " Also, as used herein, the terms "has," "have," "having," or the like are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "based, at least in part, on.

Claim 1:
A track pad (<NUM>) for a continuous track assembly, comprising:
a body (<NUM>) formed of a first material with a first hardness;
at least one roller-engaging surface (<NUM>) configured to engage a roller (<NUM>) of the continuous track assembly,
wherein the roller-engaging surface (<NUM>) is formed of a second, different, material with a second hardness that is greater than the first hardness, and wherein the second material is configured to engage the roller (<NUM>); and
characterised by the provision of two roller-engaging surfaces (<NUM>) and two sprocket-engaging surfaces (<NUM>), wherein a first sprocket-engaging surface (<NUM>) configured to engage a sprocket when operated in a first direction and a second sprocket-engaging surface (<NUM>) configured to engage a sprocket when operated in a second direction, said first and second sprocket-engaging surfaces (<NUM>) being formed of the second material;
by the provision of one or more bushings (<NUM>) configured to link the track pad (<NUM>) to another track pad (<NUM>), wherein the one or more bushings (<NUM>) are located in the body (<NUM>) by suspending or placing them in a casting mold used for the casting of the track pad (<NUM>) at the time of manufacture and are formed of the second material; and
wherein the first material is a metal material and the second material is a ceramic material.