WO2025118022A1

WO2025118022A1 - Disc brake rotor wear indicator

Info

Publication number: WO2025118022A1
Application number: PCT/AU2024/051306
Authority: WO
Inventors: Ian John CAMPBELL
Original assignee: FMP Group Australia Pty Ltd
Current assignee: FMP Group Australia Pty Ltd
Priority date: 2023-12-06
Filing date: 2024-12-05
Publication date: 2025-06-12
Anticipated expiration: 2026-06-06
Also published as: AU2024202276B1

Abstract

A disc brake rotor (1) comprising: a disc-shaped rotor body (3) having at least a first wear surface (5) and an opposite second wear surface (7); and at least one wear indicator (9) at the first wear surface (5), wherein the wear indicator (9) includes at least one indentation (11) at the first wear surface (5), and wherein the at least one indentation includes a variable depth (12), wherein the at least one indentation (11) forms visual indicia (13) to indicate a state of wear (15) of the disc brake rotor (1).

Description

"Disc brake rotor wear indicator"

Technical Field

[0001] The present disclosure relates to disc brake rotors. This includes disc brake rotors for disc brake systems in vehicles including cars, trucks, and motorcycles.

Background

[0002] Brake systems, such as a friction brake, may include one movable surface, such as a rotating disc (such as a “rotor”) or drum, and a brake lining (such as a “brake pad”) that is movable to contact the rotating disc. The contact between the movable surface and the brake lining results in friction force between the two surfaces which slows rotation of the movable surface.

[0003] In one application, the brake system is incorporated in a motor vehicle. The brake system is an important part of controlling the motor vehicle by selectively causing the vehicle to slow down as well as maintaining a stationary position when at a stop. When activated, the brake system may convert a substantial portion of the kinetic energy of the vehicle to thermal energy.

[0004] The friction between the brake lining and movable surface also results in wearing of one or both surfaces. Typically the brake lining is the consumable component that has the most wear. In a disc brake system, the consumable brake lining is part of a brake pad.

However, the disc brake rotor also wears and, with prolonged use, also requires replacement. Over time, wearing of these components can diminish the performance of the brake system and therefore these components may need to be serviced and replaced periodically.

[0005] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims. [0006] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary

[0007] There is disclosed a disc brake rotor comprising: a disc-shaped rotor body having at least a first wear surface and an opposite second wear surface; and at least one wear indicator at the first wear surface, wherein the wear indicator includes a plurality of indentations at the first wear surface, and the plurality of indentations comprise: a first indentation having a first annular groove with a variable first indentation depth; and a second indentation having a second annular groove, wherein the first annular groove and the second annular groove are concentric; wherein the plurality of indentations form visual indicia to indicate a state of wear of the disc brake rotor.

[0008] The visual indicia may include a plurality of visually identifiable indentations to indicate respective states of wear of the friction body. This may assist the user in providing further granularity regarding the state of wear. For example, that the rotor is serviceable, the rotor is serviceable but will require replacement in the near future, and the rotor is worn and must be replaced, etc.

[0009] The indentations on the first wear surface may, depending on configuration of the vehicle and wheel, enable a user to inspect the visual indicia without removing the wheel. This can be useful for quick inspection by an end user that may not have the equipment or skills to remove the wheel and to measure the thickness of the rotor. [0010] In some examples, the visual indicia include a visible shape or configuration of at least one of the indentations. In some examples, the visual indicia comprise a width of at least one indentation.

[0011] In some examples, the first annular groove has an outer diameter and an inner diameter, wherein a first indentation depth is variable between the outer diameter and the inner diameter to indicate the respective state of wear of the disc-shaped rotor body.

[0012] In some examples, the first indentation depth is progressively deeper from the outer diameter to the inner diameter. In alternative examples, the first indentation depth is progressively deeper from the inner diameter to the outer diameter.

[0013] In some examples, the second annular groove has a second outer diameter and a second inner diameter, wherein a second indentation depth is variable between the second outer diameter and the second inner diameter to indicate the respective state of wear of the disc-shaped rotor body.

[0014] In some examples, the second indentation depth is progressively deeper from the second outer diameter to the second inner diameter. In alternative examples, the second indentation depth is progressively deeper from second inner diameter to the second outer diameter.

[0015] In some examples, the first and second annular grooves are concentric and wherein the second outer diameter of the second annular groove is smaller than the inner diameter of the first annular groove.

[0016] In some examples, the plurality of indentations comprise a third indentation having a circular shape with a third outer diameter. The second annular groove has a smaller diameter than the first annular groove, and the circular shape of the third indentation has a smaller diameter than the second annular groove . The circular shape of the third indentation is at a centre of the concentric first and second annular grooves.

[0017] In some examples, the third indentation has a third indentation depth that is variable between the third outer diameter and a centre. In some examples, the third indentation depth is progressively deeper from the third outer diameter to the centre. [0018] In some examples, the third indentation has a concave or convex shape.

[0019] In some examples of the disc-brake rotor, the third indentation is located at a centre of the first annular groove. In further examples, the first and second annular grooves are concentric.

[0020] In some examples of the disc-brake rotor, a maximum third indentation depth is deeper than a maximum second indentation depth. The maximum second indentation depth can also be deeper than a maximum first indentation depth. This provides indentations that are visibly worn away progressively (i.e. the first indentation can be more easily seen to be worn away first, followed by the second indentation, and followed by the third indentation).

[0021] In some examples of the disc brake rotor, the wear indicator comprises a pattern, wherein the pattern indicates the state of wear based on the size and configuration of a worn pattern.

[0022] In some examples of the disc brake rotor, the at least one indentation has a variable depth along a length of the indentation, and wherein the visual indicia include the length of the at least one indentation.

[0023] In some examples of the disc brake rotor, the at least one wear indicator comprises a plurality of wear indicators radially and angularly spaced on the first wear surface.

[0024] In some examples the disc brake rotor further comprises at least one further wear indicator at the second wear surface, and wherein the at least one further wear indicator includes at least one further indentation with a further variable depth. The at least one further indentation also forms visual indicia to indicate the state of wear of the disc brake rotor.

[0025] There is also provided a disc brake rotor comprising a disc-shaped rotor body having at least a first wear surface and an opposite second wear surface; and at least one wear indicator at the first wear surface, wherein the wear indicator includes a plurality of indentations at the first wear surface. The plurality of indentations comprises: a first indentation, in the form of a first annular groove, including a first indentation depth from the first wear surface; a second indentation, in the form of a second annular groove, including a second indentation depth from the first wear surface. The first annular groove and the second annular groove are concentric. The first indentation depth is different to the second indentation depth, and the shape, configuration, and/or visibility of the plurality of indentations indicate a respective state of wear of disc-shaped rotor body.

[0026] There is also provided a rotary cutting tool to form a wear indicator comprising a plurality of indentations at a wear surface of a disc brake rotor, the tool comprising:

- a shank configured to be received in a rotary drive, wherein the rotary drive rotates the rotary cutting tool around a rotation axis;

- a first set of cutting teeth, radially spaced from the rotation axis, configured to cut a first annular groove of a first indentation at the wear surface, wherein the first set of cutting teeth are angled to enable cutting of the first indentation with a variable depth;

- at least one further set of cutting teeth configured to cut one or more additional indentations at the wear surface, wherein the at least one further set of cutting teeth comprises:

- a second set of cutting teeth, radially spaced between the first set of cutting teeth and the rotation axis, and configured to cut a second annular groove of a second indentation at the wear surface that is concentric to the first annular groove of the first indentation, wherein the plurality of indentations form visual indicia to indicate a state of wear of the disc brake rotor.

[0027] In some examples of the rotary cutting tool, the at least one further set of cutting teeth are angled to enable cutting of the one or more additional indentations with variable indentation depth.

[0028] In some examples of the rotary cutting tool, the at least one further set of cutting teeth comprises the second set of cutting teeth configured to cut the second annular groove with variable indentation depth at the second indentation at the wear surface. [0029] In some examples of the rotary cutting tool, the at least one further set of cutting teeth comprises: a third set of cutting teeth configured to cut a third indentation having a circular shape.

[0030] In some examples of the rotary cutting tool, the third set of cutting teeth are proximal to the rotation axis to enable the rotary cutting tool to cut a third indentation at a centre of the annular groove of the first indentation.

[0031] In some examples of the rotary cutting tool, the third set of cutting teeth are configured to cut the third indentation with variable indentation depth. In some examples, the third indentation has a concave shape.

[0032] In some examples of the rotary cutting tool, the first set of cutting teeth and/or at least one further set of cutting teeth are configured to cut different respective depths for respective indentations.

[0033] In some examples, the rotary cutting tool further comprising a stop surface to limit the cutting depth of the rotary cutting tool.

Brief Description of Drawings

[0034] Examples of the present disclosure will be described with reference to:

[0035] Fig. 1 is a perspective view of a disc brake rotor with a wear indicator;

[0036] Fig. 2 is a cross-section of part of a disc brake rotor and showing indentations of the wear indicator;

[0037] Fig. 3 is a graphical representation of a wear indicator in an unworn state in accordance with a first example;

[0038] Fig. 4 is a side view of a portion of the disc brake rotor illustrated a first wear surface and an opposite wear surface, and the thickness of a rotor body 3;

[0039] Fig. 5 is a view of the disc brake rotor 1 with a single wear indicator of Fig. 4; [0040] Fig. 6 illustrates a sequence of the visual indicia formed by the wear indicator at various states of wear;

[0041] Fig. 7 illustrates another example of a wear indicator with multiple concentric annular grooves;

[0042] Figs. 8(a) to 8(c) illustrate another example of a wear indicator in the form of a pattern and showing the pattern in various states of wear;

[0043] Figs. 9(a) to 9(c) illustrates yet another example of a wear indicator in another pattern and showing the pattern in various states of wear;

[0044] Fig. 10(a) illustrates a further example of a wear indicator with variable length along a length of an indentation;

[0045] Fig. 10(b) is a cross-section of the wear indicator of Fig. 10(a);

[0046] Fig. 11 illustrates an example of a disc brake rotor with multiple wear indicators;

[0047] Fig. 12 illustrates an example of a rotary cutting tool to form a wear indicator shown in Fig. 3;

[0048] Fig. 13(a) illustrates another example of a wear indicator with multiple indentations, each having a consistent depth;

[0049] Fig. 13(b) is a cross-section of the wear indicator of Fig. 13(a) illustrating indentations with constant respective depths;

[0050] Fig. 14(a) is an end view of another example of a rotary cutting tool to form a wear indicator; and

[0051] Fig. 14(b) is a cross-section of the rotary cutting tool of Fig. 14(a); and

[0052] Figs. 15(a) and 15(b) illustrates another example of a wear indicator. Description of Embodiments

[0053] Overview

[0054] Fig. 1 illustrates a disc brake rotor 1 the comprises a disc-shaped rotor body 3 that has a first wear surface 5. Typically, the disc-shaped rotor body 3 has a second wear surface 7 opposite the first wear surface 7.

[0055] At least one wear indicator 9 is located at the first wear surface 5. The wear indicator 9 includes at least one indentation 11. This indentation 11 forms visual indicia to indicate a state of wear of the brake rotor 1.

[0056] When braking is required, brake calipers force friction surfaces of brake pads against the wear surface(s) 5, 7 of the rotating rotor body 5. This converts kinetic energy of the rotating rotor into thermal energy. As a consequence of friction, both the brake pads and the rotor body 3 progressively wear away. Typically, the disc-shaped rotor body 3 will decrease in thickness (the thickness 14 between the first wear surface 5 and the second wear surface 7 as illustrated in Fig. 4).

[0057] The shape, depth, and/or configuration of the indentations can be used to indicate different states of wear. For example, an indentation 11 in the form of a groove may have variable depth along a length of the groove (or variable depth across the width of the groove). As the first wear surface 5 is worn down, this causes a change in the visible indentation such as a reduced length of the groove (or reduced width of the groove). Other examples, include a plurality of indentations 11, where the indentations have different depths such that visual confirmation of indentations 11 that remain after use can be used as an indication of the state of wear. Variations of different types and styles of indentations and visual indicia will be described in further detail below.

[0058] Fig. 12 shows a rotary cutting tool 101 to form the wear indicator 9 at a disc brake rotor 1. This rotary cutting tool 101 includes a shank 103 to be received in a rotary drive 105 to rotate the tool 101 around a rotation axis. The tool 101 also includes a first set 121 of cutting teeth to cut an annular groove 24 of a first indentation at a wear surface of a disc brake rotor 1. The tool 101 also includes at least one further set 130 of cutting teeth configured to cut one or more additional indentations 11 at the wear surface 5.

[0059] Disc brake rotor

[0060] Figs. 1 and 4 illustrate an example disc brake rotor 1. The rotor typically forms part of the unsprung mass of the vehicle whereby the rotor 1 is connected to a rotating hub.

[0061] In this example, the disc brake rotor 1 has a disc-shaped rotor body 3 with a first wear surface 5 and an opposite second wear surface 7. These wear surfaces are substantially planar and parallel to each other. This example also has a rotor body 3 with vanes 12 between the wear surfaces 5, 7 to assist cooling of the disc-shaped body 3.

[0062] In other examples, the disc-shaped rotor body 3 may be solid. In further examples, the disc- shaped rotor body 3 may have one or more slots at the wear surfaces 5, 7. In some examples, the disc-shaped rotor body 3 may be cross-drilled with apertures through the rotor body 3.

[0063] In some examples, the disc-shaped rotor body 3 further comprises a drum-shaped portion proximal to the hub to provide a rotating drum. The drum- shaped portion may form part of a further braking system such as a parking brake that operates in conjunction with a brake shoe.

[0064] The thickness 14 of the disc-shaped rotor body, (where the thickness is the distance between the first wear surface 5 and the opposite second wear surface 7 as illustrated in Fig.

4) is an important measure of wear on the disc brake rotor. During use of the brake, calipers of the disc brake system drive corresponding brake pads together and the friction causes the rotor body 3 to wear such that the thickness 14 reduces. If the rotor thickness is too thin, this can cause problems such as:

• Reduced thermal mass of the rotor that can reduce braking capacity;

• Weakened structure of the rotor, that may lead to structural failure or warping; and

Loss of braking power and increased stopping distances. [0065] Referring to Fig. 4, the thickness 14 includes an initial unworn thickness 18 and a designed minimum thickness 16 whereby the rotor 1 must be replaced.

[0066] The desired thickness 14 of the disc-shaped rotor body 3 is typically selected by design of the braking system or selected by design of the vehicle.

[0067] In some examples, passenger car may be designed to have a disc-brake rotor with a thickness 14 of approximately between 20mm to 40mm. In some examples, these are selected between 25mm and 30mm.

[0068] In some examples, a braking system may be designed to have a new (unused) rotor body 3 with an unworn thickness 18 of 28mm. The brake manufacturer may design or specify that the brake rotor 3 has a specified wear of 2mm at which point the rotor is considered worn and must be replaced. That is, if the thickness 14 is at a minimum thickness 16 of 26mm or less, the rotor 1 must be replaced.

[0069] It is to be appreciated that in some examples, the specified allowable wear of a disc brake rotor 1 may be different based on other parameters. This may include:

• a particular type of vehicle - this may include a car manufacturer providing their own specifications for maximum wear;

• the anticipated use of the vehicle - for example if the brake rotor is to be used in extreme temperature environments, off-road, towing, or motorsport, the maximum amount of wear may be reduced (i.e. requiring a larger thickness 14 for safe operation);

• the maximum mass of the vehicle - a heavier vehicle may require more thickness 14 to increase thermal mass for safe operation;

• the number or types of brakes on the vehicle - whether the disc brake rotor is used in a vehicle employing similar disc brakes or whether some wheels are utilising other braking systems such as drum brakes. [0070] In some cases, the wear on the first wear surface 5, and the second wear surface 7 may need to be monitored. Thus in addition to a wear indicator 9 on the first wear surface 5, at least one further wear indicator, with a further indentation, is provided at the second wear surface 7. The further wear indicator may be similar or the same as the wear indicator 9 on the first wear surface 5 and also forms visual indicia 13 to indicate the state of wear 15 of the disc brake rotor 1. In ideal situations, the first and second wear surfaces 7 wears evenly so that the respective wear indicators should show similar states of wear. Uneven states of wear may indicate problems with the braking system that require rectification.

[0071 ] Wear indicator 9 and visual indicia 13

[0072] The wear indicator 9, in particular the at least one indentation 11, is configured to provide visual indicia 13 of the state of wear. An example of a wear indicator 9 on a disc brake rotor 1 is shown in Figs 1 and 5. As the wear surfaces 5, 7, are worn down from friction with the brake pad, the indentations 11 progressively becomes shallower (with respect to the remaining wear surface). This can cause a change in the visible 10 shape or configuration of the at least one indentations 11 (when compared with an unworn disc brake rotor 1).

[0073] In some examples, the indentations may include a variable depth 12 across a width of the indentation 11. For example, the indentation 11 may include a groove 24 and the depth from one side of the groove 24 to the other side of the groove may be progressively deeper. Thus as the wear surface 5 is worn, the width of the groove 24 will decrease.

[0074] In an alternative example, the indentation 11 includes a groove 24 whereby the groove may have a U-shaped or V-shaped cross-section. Similarly, as the rotor 1 is worn down, the width of the groove 24 also reduces.

[0075] In another example, the indentation has a variable depth 12 along a length 26 of the indentation 11. As the disc-brake rotor 1 is worn down, the length 26 of the indentation 11 will become progressively shorter. Thus the length 26 of the indentation 11 in these examples could be used as visual indicia of the state of wear 15.

[0076] First example of visual indicia [0077] Figs. 2 and 3 illustrates a first example of the wear indicator 9 where the disc brake rotor 1 is unworn. In particular Fig. 2 shows a cross-section of the indentations 11 from the first surface wear surface 3. This includes showing indentations 11 with variable depths 12. Fig. 3 illustrates the indentations 5 when viewed from a surface normal perspective to the wear surface 5, whereby the unworn indentations serve as visual indicia 13 to indicate an unworn state of wear 15.

[0078] The indentations 11 are configured as concentric circles for easy visibility and recognition. The first indentation 21 is in the form of an annular groove 24 and forms the outer circle visible in Fig. 3. The first annular groove 24 has an outer diameter 25 and an inner diameter 27, wherein the first indentation depth 23 is variable between the outer diameter 25 and the inner diameter 27. In this example, the first indentation depth 23 becomes progressively deeper from the outer diameter 25 to the inner diameter 27. Thus in the unworn state, the original outer diameter 25 should be visible. However with some slight wearing of the first wear surface 25, the outer diameter 25 that will be visible decreases in diameter. In some examples, the decrease in diameter is visible or recognisable by a human eye (or by a camera system, or other sensor). However, in this example, the reduction of the outer diameter 25 would result in a relatively thinner width of the annular groove 24 which may be more recognisable to a human. In particular, the relative width of this outer circle may be in contrast to the width of other indentations (such as the other circles).

[0079] This example also includes a second indentation 31 in the form of a second annular groove 34. The second annular groove 34 has a second outer diameter 35 and a second inner diameter 37. The second indentation depth 33 is variable between the second outer diameter 35 and the second inner diameter 37. Similar to the first indentation, the variable depth can also be used to indicate wear. Specifically, in this example the second indentation depth 33 is progressively deeper from the second outer diameter 35 to the second inner diameter 37.

[0080] In this example, the second indentation depth 33 is designed to be deeper than the first indentation depth 23 such that during progressive wear the first annular groove 24 will wear away and become visibly thinner (and disappear) followed by the second annular groove 34 starting to become thinner. This stepped approach where changes to the visibility (and configuration) the first annular groove 24 occurs first before the second annular groove 34 can improve determination (and granularity) of the state of wear 15. [0081] As the first annular groove 24 and second annular groove 34 are concentric, and to improve easy distinction between the two indentations, the second outer diameter 35 of the second annular groove 34 is smaller than the inner diameter 27 of the first annular groove 24. Between the annular grooves 24, 34 are raised portions 30 (relative to the grooves), where these raised portions are generally on the same plane as the wear surface 5 (when the disc brake rotor 1 is in a new condition).

[0082] At the centre of the concentric circles is a third indentation 41 having a circular shape 44 with a third outer diameter 45. The third indentation has a third indentation depth 43 that is variable between the third outer diameter 45 and a centre 47. In this example, the third indentation depth 43 is progressively deeper from the third outer diameter 45 to the centre 47. In this example, the third indentation includes, at least in part a concave shape. However, it is to be appreciated that alternative examples may have different shapes, such as U- shape, or V- shape cross-sections, or even a convex shape where the centre has a shallower depth compared to the third outer diameter 45 of the third indentation 41.

[0083] In this example, a maximum third indentation depth 43 is deeper than a maximum second indentation depth 33. Furthermore, the maximum second indentation depth 33 is deeper than a maximum first indentation depth. This stepped approach in depth can simplify identification of the state of wear as a user can expect initial wear to affect the configuration (in particular width) of the first annular groove 24, followed by changes to the second annular groove 34, and finally followed by changes to the third indentation 41.

[0084] In some examples, the variable depths are selected such that the entire first annular groove 24 is first worn away before noticeable changes of width to the second annular groove 34 are visible. In turn (and with further wear), the entire first and second annular grooves 24, 34 are worn away before noticeable changes of diameter of the third indentation 41 are visible. This can further aid easy identification of the state of wear 15.

[0085] Method of determining various states of wear and visual indicia

[0086] Fig. 6 illustrates a sequence that shows the wear indicator 9, of the first example, providing visual indicia 13 in various states of wear. A first visual indicia 81 corresponds to a new and unworn disc brake rotor 1, whereby all three indentations 21, 31, 41 are visible. This includes the full width of the grooves, including the width of the annular groove 24 between the original outer diameter 25 and the inner diameter 27.

[0087] A second visual indicia 82 in the sequence corresponds to an approximately 50% worn rotor. The width outer annular groove 24 that correspond the first indentation 21’ begins to narrow. This is due to the variable depth 23 of the groove 24 (which is deeper towards the inner diameter) that results in progressive narrowing off the annular groove 24 towards the inner diameter 27. In this example, the visual size and shape of the second and third indentations 31, 41 is substantially unchanged from the first visual indicia 81 as the corresponding indentation depths 33, 43 are sufficiently deep so that wearing away of the wear surface 5 does not alter the general visual appearance.

[0088] A third visual indicia 83 corresponds to an approximately 65% worn rotor (i.e. with ~ 45% of the designed wear surface remaining). The outer annular groove 24 of the first indentation 21” has a narrow width that indicates the wear surface 5 has been worn such that remaining first indentation depth 23 is very shallow, and almost gone. In this example, the visual size and shape of the second and third indentation 31, 41 remains substantially unchanged.

[0089] A fourth visual indicia 84 corresponds to an approximately 75% worn rotor. In this example the wear surface 5 has worn away such that the first indentation 21 no longer exists and consequently there is no visible outer groove 24. The second annular groove 34 of the second indentation 31 is visible and is similar, or slightly narrower than the original width of the groove 34. The visual features of the third indentation 41 remains substantially the same as original.

[0090] A fifth visual indicia 85 corresponds to an approximately 80% worn rotor 1. In this example the width of the second annular groove 34 has worn to be visibly narrower than the original unworn width. The visual features of the third indentation 41 remains substantially the same as original.

[0091] A sixth visual indicia 86 corresponds to an approximately 85% worn rotor 1. The wear surface 5, 6 has worn away such that both the first and second indentations 21, 31 no longer exists and thus there are no visible first and second annular grooves 24, 34. As the third indentation 41 has a relatively deeper indentation depth 43, the general size and shape of the third indentation 41 is still visible.

[0092] A seventh visual indicia 87 corresponds to an approximately 90% worn rotor. In this example, the size of the third indentation 41’ is now visibly smaller than original.

[0093] An eighth visual indicia 88 corresponds to an approximately 95% worn rotor. In this example, the third indentation 41” is barely visible as the wear surface 3 has almost worn away to the level of the maximum depth of the third indentation 41”.

[0094] When the disc brake rotor 1 is fully worn and must be replaced (i.e. 100% worn) then all the indentations 21, 31, 41 are no longer visible.

[0095] In this first example, there is more granularity of the state of wear as the disc brake rotor 1 approaches the 100% worn state. This can be important as a user, or mechanic, needs to closely monitor the actual wear state in case the disc brake rotor 1 requires imminent replacement. On the other hand, granularity between an initial unworn state to 50% worn state may not be as important as there is a substantial buffer until the disc brake rotor 1 needs to be replaced. Nonetheless, it is to be appreciated that in alternative examples, more granularity of information can be provided in the earlier states of wear and the visual indicia may enable determination of state of wear more evenly between the unworn state to the fully worn state.

[0096] Variations of visual indicia

[0097] It is to be appreciated that variations or alternatives to the visual indicia may also be used. In some examples of the visual indicia 91, additional indentations, such as additional concentric grooves as shown in Fig. 7 can provide more granularity and/or additional clarity when distinguishing between different states of wear.

[0098] In some alternatives, the variable depth indentations of the annular grooves may be configured such that the annular grooves and/or circle at the centre of the visual indicia 91 wear away sooner than the outer annular grooves. This may be advantageous at higher states of wear as it may be easier to spot a large annular groove becoming thinner as the visual indicia in comparison with a single small central indentation that becomes smaller and smaller (as shown in Fig. 6).

[0099] In some alternative examples, the first indentation depth 23 is progressively deeper from a relatively shallower inner diameter 27 to a relatively deeper outer diameter 25. Similarly, the second indentation depth 33 may be progressively deeper from the second inner diameter 37 to the second outer diameter. The third indentation 41 may have, at least in part, a convex shape. This configuration results in changing visual indicia from a centre of the wear indicator outwards as the rotor 1 is progressively worn. This results in the outer diameters 25, 35, 45 of the indentations to be visible for as long as possible (until the indentation is fully worn away) which may assist in easier identification.

[0100] In some examples, the wear indicator 9 includes visual indicia may be in the form of a pattern 51, wherein the pattern indicates the state of wear 15 based on a size and configuration of the worn pattern 51. Referring to Figs. 8(a) to 8(c) this shows a pattern 51 in various states of wear. The pattern 51 in an unworn rotor includes five parallel grooves 53. Each of the five grooves have a variable depth along the length, and the overall depth of the grooves is different to those of adjacent grooves. Fig. 8(a) shows the pattern 51 when the rotor 1 is unworn such that all five grooves 53 are visible. Fig. 8(b) illustrates a partially worn rotor 1 where approximately 10% of the designed wear has been worn away. In this case, the first shallow groove 55 has worn such that half of the variable depth groove is gone and that the length of the first shallow groove 55’ is half the length. With further wear to approximately 80% (not shown), the first shallow groove 55 may be gone and no longer visible such that only four parallel grooves 53 remain. Fig. 8(c) illustrates the pattern 51 when the rotor is approximately 50% worn, whereby only two and a half grooves 53 are visible. Thus in the example of Figs. 8(a) to 8(c), each of the five grooves corresponds to approximately 20% range of the state of wear, and the length of the groove may be used to approximate the state of wear in that 20% range.

[0101] Figs. 9(a) and 9(b) illustrates another example of a pattern 51 in the form of a stylised X. This includes indentations in the form of a first groove 52 and second groove 54 to form the X. The first groove 52, for example may have a depth starting from one end of approximately 1mm and slowly transitioning (i.e. tapering) to the wear surface 5. The second groove 54 may have a variable depth of 1mm at one end that transitions to 2mm at the other end. Thus as the wear surface initially wears, the first groove 52 gets shorter whilst the second groove 54 remains substantially the same (as shown in Fig. 9(b)). Additional wear results in the first groove 52 completely worn away with only the second groove 54 remaining as shown in Fig. 9(c). This would correspond to approximately 1mm being worn away from the unworn rotor. Yet even more wear results in the second groove 54 getting shorter as shown in Fig. 9(d), which would be indicative of wear of between 1mm and 2mm of the rotor from the original unworn state.

[0102] Figs. 10(a) and 10(b) illustrate a variation where the at least one indentation 11 has a variable depth 12 along a length 26 of the indentation 11. Fig. 10(a) illustrates a view looking at a portion of the wear surface with the wear indicator. The visual indicia 13 includes the visible length 26 of the at least one indentation. Fig. 10(b) illustrates a cross section of the indentation and the rotor body 3 and the variable depth 12 of the indentation 11.

[0103] Fig. 11 illustrates another example of a disc brake rotor with a plurality of wear indicators on the first wear surface. These are radially and angularly spaced on the wear surface (around the hub axis) so that even if one of the wear indicators 9 are covered by a brake caliper or part of a wheel, another wear indicator may be visible.

[0104] Cutting tool

[0105] Fig. 12 illustrates a cross-section of an example of a rotary cutting tool 101 to form the wear indicator 9. This illustrated rotary cutting tool 101 is configured to form the plurality of indentations 17 (11, 21, 31, 41) at a wear surface 5, 6 such as the example wear indicator 9 shown in Fig. 3.

[0106] The rotary cutting tool 101 includes a shank 103 configured to be received in a rotary drive 105 that rotates the tool around a rotation axis 108. The rotary drive may be part of a machine tool, such as a computer numerical control (CNC) machine.

[0107] The tool includes a first set 121 of cutting teeth configured to cut the annular groove 24 of a first indentation 21 at the wear surface 5, 6 of a disc brake rotor 1. At least one further set 130 of cutting teeth are configured to cut one or more indentations 11 at the wear surface. [0108] One or more of the sets 121, 130, 131, 141 of cutting teeth can be angled to enable cutting of an indentation 23, 33, 43 of a variable depth. By angled, this means the cutting surface of the teeth are at an angle between the rotation axis and a perpendicular plane (to the rotation axis). It is to be appreciated that selection of the angle of the cutting teeth affects the variable depth of the indentation.

[0109] In some alternatives, the first set 121 of cutting teeth and/or the further set 130, 131, 141 of cutting teeth are configured to cut different respective depths 23, 33, 43 for the respective indentations 11. The rotary cutting tool 101, in this example includes a stop surface 151 to limit the cutting depth of the rotary cutting tool 101. This stop surface 151 may be configured to have an annular surface that is configured (during cutting operations) to abut with the wear surface 5, 6 at the specified depth. Ideally, the abutment of the stop surface 151 and the wear surface 5, 6 is in parallel contact so that the stop surface 151 does not cut into the wear surface 5, 6.

[0110] In this example, the further set 130 of cutting teeth includes a second set 131 of cutting teeth configured to cut a second annular groove 34 of the second indentation 31 at the wear surface. In additional, or alternative examples, the further set of cutting teeth 130 includes a third set 141 of cutting teeth configured to cut the third indentation 41 that is in the form of a circular shape as illustrated in Fig. 3.

[0111] In the example of Fig. 12, the sets of teeth enable formation of concentric annular grooves and circles of the wear indicator as illustrated in Fig. 3. This is enabled by having the first set of cutting teeth radially spaced from the rotation axis 108 and the third set 141 of cutting teeth proximal to the rotation axis 108. Thus the third indentation 41 is formed at the centre of the annular groove 24 of the first indentation 21.

[0112] The second set 131 of cutting teeth is radially spaced between the third set 141 of cutting teeth and the first set 121 of cutting teeth to enable the rotary cutting tool to cut the second annular groove to be concentric to the first annular groove 24.

[0113] In some applications, a common physical brake rotor 1 design could be used for different applications. For example, a car manufacturer may use the type of rotor 1 but for different models of cars. The different models of cars may have different thickness specifications for what constitutes a fully worn rotor that needs replacements. In some examples, the different application or specification may be dictated by local laws, regulations, or intended use for the vehicle. That is a model of vehicle used of one market/application may have more stringent requirements than for another market/application.

[0114] To that end, a car manufacturer (or supplier) may have different rotary cutting tools (101) with respective teeth patterns (and depths) to apply the wear indicators 9 appropriate for the intended use of that brake rotor 1.

[0115] Mobile phone, communication device or scanner

[0116] An informed user may be able to estimate the state of wear based on the visual indicia 13 with the naked eye. However, in some circumstances a user may be a novice or does not remember how the visual indicia corresponds to states of wear. In some examples, a mobile communication device (such as a smartphone, tablet) or other device with a camera and processor could assist in displaying the state of wear to a user. For example, an application on such portable communication devices can take an image of the visual indicia (captured by the camera) and calculate (or estimate) the state of wear based on the relative size and configuration of the indentations 11, and/or by the number of indentations 11 remaining. The state of wear can then be output on a display or audibly by a speaker of the mobile communication device. In some examples, a specific purpose device is made for capturing images of the visual indica and presenting the results to the user. Such as specific purpose device may be useful for convenience and high volume of scans, such as at a (fuel) service station, a mechanic or other workshop, weigh stations, vehicle inspection stations, public parking stations, etc.

[0117] Variations

[0118] In alternative examples (as illustrated in Fig. 13(a) and shown as a cross-section in Fig. 13(b)), the at least one wear indicator 9’ includes a plurality of indentations as the first wear surface 5. The plurality of indentations 11 includes: a first indentation 21 that includes a first indentation depth 23 from the first wears surface; and a second indentation 31 with a corresponding second indentation depth 33 from the first wear surface 5. The first indentation depth 23 is different to the second indentation depth 33. In such alternative examples, the first and second indentations depths 23, 33 may each have a corresponding consistent depth (in contrast to examples above described with variable depths). The shape, configuration and corresponding visibility of the plurality of indentations could then be used to indicate a respective state of wear of the disc- shape rotor body 3. For example, an unworn disc brake rotor 1 may have both the first and second indentations 21, 31 to be visible. A partially worn disc brake rotor 1 may be worn such that the wear surface 5 is worn to, or past, the original depth of the first indentation 21 such that the first indentation 21 is no longer visible but where the second indentation 33 is still visible. A disc brake rotor 1 worn past the specified design may have none of the plurality of indentations 11, 21, 31 to be visible. In this example, the base of the groove is substantially parallel with the wear surface 5.

[0119] There is also disclosed a rotary cutting tool 101 to cut the alternative wear indicator 9’ of Figs. 13(a) 13(b). This include cutting teeth with similarities to those discussed above but configured such that the teeth have edges to cut indentations so that the depth is consistent.

[0120] Another example of a rotary cutting tool 101’ is illustrated in Figs. 14(a) and 14(b). Fig. 14(a) illustrates an end view of the wear indicator that is configured to rotate and machine away indentations 11 at the wear surface 5. This includes grinding surfaces 121’, 131’, and 141’, configured to machine the indentations 11. Fig. 14(b) is a cross-section of Fig. 14(a) to show the profile of the grinding surfaces. The grinding surfaces may be shaped to grind one or more indentations at a variable depth. Between the grinding surfaces 121’, 131’, 141’ are voids 150 to enable raised portion 30 of the wear surface 5 to remain in between the cut annular grooves 11. At the depths of the void 150 are stop surfaces 151 that prevent the rotary cutting tool 101’ to machine too far into the wear surface 1. The stop surfaces 151 may be configured to be smooth to reduce grinding of the wear surface 5 of the rotor 1.

[0121] Figs. 15(a) and 15(b) illustrates another example of the wear indicator 9 with variable depth indentations 11. In particular, these figures illustrate the wear indicator 9 and indentations 11 with corresponding dimensions for the diameter and depths of the indentations 21, 31, 41. This includes an outer diameter 25 of approximately 15mm and an inner diameter 27 of approximately 11mm for the first indentation 21 (annular groove 24). The depth of the first indentation 21 varies between 0.2mm and 0.35mm. The second outer diameter 35 is approximately 9mm and the second inner diameter is approximately 5mm for the second indentation 31. The depth of the second indentation 31 varies between 0.35mm to 0.49mm. The third indentation 41 at the centre has a diameter of approximately 5mm and has a depth that varies between 0.49mm at the outside to approximately 0.6mm at the centre.

[0122] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A disc brake rotor (1) comprising: a disc-shaped rotor body (3) having at least a first wear surface (5) and an opposite second wear surface (7); and at least one wear indicator (9) at the first wear surface (5), wherein the wear indicator (9) includes a plurality of indentations (11) at the first wear surface (5), and the plurality of indentations (11) comprise: a first indentation (21) having a first annular groove (24) with a variable first indentation depth (23); and a second indentation (31) having a second annular groove (34), wherein the first annular groove (24) and the second annular groove (34) are concentric, wherein the plurality of indentations (11) form visual indicia (13) to indicate a state of wear (15) of the disc brake rotor (1).

2. A disc brake rotor (1) according to claim 1 wherein the visual indicia (13) include a visible (10) shape or configuration of at least one of the plurality of indentations (11).

3. A disc brake rotor (1) according to any one of the preceding claims wherein the visual indicia (13) comprise a width (22) of at least one of the plurality of indentations (11).

4. A disc brake rotor (1) according to any one of the preceding claims, wherein the first annular groove (24) has an outer diameter (25) and an inner diameter (27), wherein the variable first indentation depth (23) is variable between the outer diameter (25) and the inner diameter (27) to indicate the respective state of wear of the disc-shaped rotor body (3).

5. A disc-brake rotor (1) according to claim 4 wherein the first indentation depth (23) is progressively deeper from the outer diameter (25) to the inner diameter (27).

6. A disc-brake rotor (1) according to claim 4 wherein the first indentation depth (23) is progressively deeper from the inner diameter (27) to the outer diameter (25).

7. A disc brake rotor (1) according to any one of the preceding claims, wherein the second annular groove (34) has a second outer diameter (35) and a second inner diameter (37), wherein a second indentation depth (33) is variable between the second outer diameter (35) and the second inner diameter (37) to indicate the respective state of wear of the discshaped rotor body (3).

8. A disc-brake rotor (1) according to claim 7 wherein the second indentation depth (33) is progressively deeper from the second outer diameter (35) to the second inner diameter (37).

9. A disc-brake rotor (1) according to claim 7 wherein the second indentation depth (33) is progressively deeper from the second inner diameter (37) to the second outer diameter (35).

10. A disc-brake rotor (1) according to any one of the preceding claims, wherein the plurality of indentations (11) comprise a third indentation (41) having a circular shape (44) with a third outer diameter (45), wherein the second annular groove (34) has a smaller diameter than the first annular groove (24), and the circular shape (44) of the third indentation (41) has a smaller diameter than the second annular groove (34), and wherein the circular shape (44) of the third indentation (41) is at a centre (47) of the concentric first and second annular grooves (24, 34).

11. A disc-brake rotor (1) according to claim 10 wherein the third indentation (41) has a third indentation depth (43) that is variable between the third outer diameter (45) and the centre (47).

12. A disc-brake rotor (1) according to claim 11 wherein the third indentation depth (43) is progressively deeper from the third outer diameter (45) to the centre (47).

13. A disc-brake rotor (1) according to claim 11 wherein the third indentation (41) has a concave or convex shape.

14. A disc-brake rotor (1) according to any one of claims 10 to 13, wherein a maximum third indentation depth (43’) is deeper than a maximum second indentation depth (33’); and wherein the maximum second indentation depth (33’) is deeper than a maximum first indentation depth (23’).

15. A disc brake rotor (1) according to any one of the preceding claims wherein the at least one wear indicator (9) comprises a plurality of wear indicators radially and angularly spaced on the first wear surface (5).

16. A disc brake rotor (1) according to any one of the preceding claims further comprising at least one further wear indicator at the second wear surface (7), and wherein the at least one further wear indicator includes at least one further indentation with a further variable depth, wherein the at least one further indentation also forms visual indicia (13) to indicate the state of wear (15) of the disc brake rotor (1).

17. A disc brake rotor (1) comprising: a disc-shaped rotor body (3) having at least a first wear surface (5) and an opposite second wear surface (7); and at least one wear indicator (9) at the first wear surface (5), wherein the wear indicator (9) includes a plurality of indentations (11) at the first wear surface (5), wherein the plurality of indentations comprise:

- a first indentation (21), in the form of a first annular groove (24), including a first indentation depth (23) from the first wear surface (5); - a second indentation (31), in the form of a second annular groove (34), including a second indentation depth (33) from the first wear surface (5), wherein the first annular groove (24) and the second annular groove (34) are concentric; and wherein the first indentation depth (23) is different to the second indentation depth (33), and the shape, configuration, and/or visibility of the plurality of indentations indicate a respective state of wear of disc-shaped rotor body (3).

18. A rotary cutting tool (101) to form a wear indicator (9) comprising a plurality of indentations (11) at a wear surface (5) of a disc brake rotor (1), the tool (101) comprising:

- a shank (103) configured to be received in a rotary drive (105), wherein the rotary drive (15) rotates the rotary cutting tool (101) around a rotation axis (108);

- a first set (121) of cutting teeth, radially spaced from the rotation axis (108), configured to cut a first annular groove (24) of a first indentation (21) at the wear surface (5), wherein the first set (121) of cutting teeth are angled to enable cutting of the first indentation (21) with a variable depth (23);

- at least one further set (130) of cutting teeth configured to cut one or more additional indentations (11) at the wear surface (5), wherein the at least one further set (130) of cutting teeth comprises:

- a second set (131) of cutting teeth, radially spaced between the first set (121) of cutting teeth and the rotation axis (108), and configured to cut a second annular groove (34) of a second indentation (31) at the wear surface (5) that is concentric to the first annular groove (24) of the first indentation (21); wherein the plurality of indentations (11) form visual indicia (13) to indicate a state of wear (15) of the disc brake rotor (1).

19 A rotary cutting tool (101) according to claim 18, wherein the at least one further set (130) of cutting teeth are angled to enable cutting of the one or more additional indentations (11) with variable indentation depth (33, 43).

20. A rotary cutting tool (101) according to either claim 18 or 19, wherein the at least one further set (130) of cutting teeth comprises:

- a third set (141) of cutting teeth configured to cut a third indentation (41) having a circular shape (44), and wherein the third set (141) of cutting teeth are proximal to the rotation axis (108) to enable the rotary cutting tool (101) to cut a third indentation (41) at a centre of the first annular groove (24) of the first indentation (21).

21. A rotary cutting tool (101) according to any one of claims 18 to 20, wherein the first set (121) of cutting teeth and/or at least one further set (130) of cutting teeth are configured to cut different respective depths (23, 33, 43) for respective indentations (11).

22. A rotary cutting tool (101) according to any one of claims 18 to 21 further comprising a stop surface (151) to limit the cutting depth of the rotary cutting tool (101).