# US 10,870,455 B2 · Track link for a track joint assembly having wear band with lengthwise-varied hardness

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- Number: US 10,870,455 B2
- Document ID: US10870455B2
- Status: Granted
- Kind: B2
- Application number: 16/128,455
- Filed: 2018-09-11
- Published: 2020-03-12
- Granted: 2020-12-22
- Earliest claimed: 2018-09-11
- Assignees: Caterpillar Inc.
- Applicants: Caterpillar Inc.
- Inventors: Kevin Steiner
- Web page: https://patentgrep.com/patent/US10870455B2

## CPC

- B62D 55/202: {Wheel engaging parts; Wheel guides on links}
- B62D 55/21: Links connected by transverse pivot pins
- C21D 1/42: Induction heating
- C21D 9/04: for rails
- B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M)
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

## Abstract

A track link for a ground-engaging track system includes an elongate link body having an upper rail surface located in part upon each of a first link strap, a second link strap, and a middle section of the track link. The upper rail surface is formed by a wear band of sacrificial wear material having a hardness that is varied lengthwise along the upper rail surface to retard scalloping of the track link during service and forming relatively softer zones in the first and second link straps and a relatively harder zone within the middle section. Methodology for making such a track link is also disclosed.

## Claims

### Claim 1

A track link for a ground-engaging track system in a machine comprising:
an elongate link body including a first link strap having a track pin bore formed therein, a second link strap having a bushing bore formed therein, and a middle section connecting between the first link strap and the second link strap;
the elongate link body further including a lower shoe-mounting surface, and an upper rail surface, the upper rail surface being located in part upon each of the first link strap, the second link strap, and the middle section, and formed by a wear band of sacrificial wear material;
the sacrificial wear material having a hardness that is varied lengthwise along the upper rail surface to form a first relatively softer zone located in the first link strap and including a softer material exposed on the upper rail surface, a second relatively softer zone located in the second link strap and including the softer material exposed on the upper rail surface, and a relatively harder zone located at least in part within the middle section and including a harder material exposed on the upper rail surface;
the sacrificial wear material having a hardness that is varied depthwise from the upper rail surface; and
the wear band is formed of the harder material outside of the first relatively softer zone and the second relatively softer zone, such that the harder material extends depthwise between the first relatively softer zone and the track pin bore and depthwise between the second relatively softer zone and the bushing bore.

### Claim 2 (depends on 1)

The track link of claim 1 wherein the relatively harder zone extends into each of the first link strap and the second link strap.

### Claim 3 (depends on 2)

The track link of claim 2 wherein the relatively harder zone is continuous.

### Claim 4 (depends on 3)

The track link of claim 3 wherein a lengthwise extent of the relatively harder zone within each of the first link strap and the second link strap is about 20% or less of a full length of the upper rail surface within the corresponding first or second link strap.

### Claim 5 (depends on 1)

The track link of claim 1 wherein each of the first lower hardness zone and the second lower hardness zone has a trough shape.

### Claim 6 (depends on 5)

The track link of claim 5 wherein the second link strap includes an end band, and the wear band extends downward to a boundary that is spaced a distance from the bushing bore that is not less than a thickness of the end band.

### Claim 7 (depends on 6)

The track link of claim 6 wherein each of the first lower hardness zone and the second lower hardness zone defines a trough depth from the upper rail surface that is less than a depth of the boundary from the upper rail surface.

### Claim 8 (depends on 1)

The track link of claim 1 wherein the first link strap is laterally offset from the second link strap such that the elongate link body forms an S-pattern.

### Claim 9 (depends on 8)

The track link of claim 8 wherein the upper rail surface is flat.

### Claim 10

A track joint assembly for a ground-engaging track system in a machine comprising:
a first track link;
a second track link;
a track pin coupling the first track link to the second track link;
each of the first track link and the second track link including a first link strap having a track pin bore formed therein, a second link strap having a bushing bore formed therein, and a middle section connecting between the first link strap and the second link strap;
each of the first and the second track links further including a lower shoe-mounting surface, and an upper rail surface, the upper rail surface being located in part upon each of the corresponding first link strap, second link strap, and middle section, and formed by a wear band of sacrificial wear material;
the sacrificial wear material having a hardness that is varied lengthwise along the upper rail surface of the corresponding first or second track link to form a first relatively softer zone of a softer material located in the first link strap, a second relatively softer zone of the softer material located in the second link strap, and a relatively harder zone of harder material located at least in part within the middle section; and
the sacrificial wear material having a hardness that is varied depthwise from the upper rail surface in the corresponding first or second track link, such that the softer material has a greatest depth from the upper rail surface at a location longitudinally between the middle section and an outer end of the respective first link strap or second link strap, and is progressively reduced in depth, from the location of greatest depth, in longitudinal directions toward each of the middle section and the outer end of the respective first link strap or second link strap.

### Claim 11 (depends on 10)

The track joint assembly of claim 10 wherein the first link strap is laterally offset from the second link strap in each of the first and the second track link so as to form an S-pattern.

### Claim 12 (depends on 10)

The track joint assembly of claim 10 wherein a gap extends between the first link strap of the first track link and the middle section of the second track link, and the relatively harder zone of the second track link extends into the corresponding second link strap such that relatively harder sacrificial wear material of the second track link is located adjacent to the gap.

### Claim 13 (depends on 12)

The track joint assembly of claim 12 wherein a roller contact width of the upper rail surface in the middle section is about twice a roller contact width of the upper rail surface in each of the first and the second link straps.

### Claim 14 (depends on 10)

The track joint assembly of claim 10 wherein the upper rail surface is flat.

### Claim 15 (depends on 14)

The track joint assembly of claim 14 wherein each of the first lower hardness zone and the second lower hardness zone has a trough shape.

### Claim 16

A track link for a ground-engaging track system in a machine made according to a method comprising:
heat treating an elongate link body having a first link strap, a second link strap, a middle section, and an upper rail surface, such that a material extending throughout the elongate link body is hardened to form a harder material;
tempering the elongate link body such that a portion of the material that forms the upper rail surface is softened to form a softer material;
forming, by way of the heat treating and the tempering of the elongate link body, a scallop-retarding pattern of material hardness that is varied lengthwise along the upper rail surface; and
the scallop-retarding pattern of material hardness forming relatively softer zones of the softer material in each of the first and the second link straps, a relatively harder zone in the middle section of the harder material, and a wear band of the harder material extending lengthwise between an outer end of the first link strap and an outer end of the second link strap and depthwise between the relatively softer zones and a first bore in the first link strap and a second bore in the second link strap, respectively.

### Claim 17 (depends on 16)

The track link of claim 16 wherein the forming of a scallop-retarding pattern of material hardness further includes forming a relatively harder zone that is continuous and extends into the first and the second link straps.

### Claim 18 (depends on 17)

The track link of claim 17 wherein the heat treating of the elongate link body further includes hardening the material to a hardness greater than 50 HRC, and the tempering of the elongate link body further includes tempering the elongate link body such that the portion of the material that forms the upper rail surface is softened from the hardness greater than 50 HRC to a hardness less than 50 HRC.

### Claim 19 (depends on 18)

The track link of claim 18 wherein the tempering of the elongate link body further includes tempering the elongate link body by way of electromagnetic induction tempering of the upper rail surface within the first and the second link straps.