AU2017210670B2 - Brake Disc with Symmetric Groove Pattern - Google Patents

Abstract

A method of arranging grooves in opposed brake band surfaces of a brake disc; said method comprising forming grooves on both sides of said brake disc; said grooves limited to a first and second set of grooves; the first set of grooves comprising arcuate grooves which extend from proximate an inner circumferential edge of said brake pad surface of said brake band to proximate a mid portion of the width of the brake band; said second set of grooves comprising arcuate grooves which extend from proximate said mid portion of the width of said brake band to proximate an outer circumferential edge of said brake band; said grooves arced and paired whereby braking performance is substantially the same in use independent of direction of rotation of said brake disc.

Description

[0001] The present invention relates to discs for vehicle brakes and, more particularly, to groove segments provided in the braking surfaces of such discs.

BACKGROUND [0002] Many arrangements of groove segments on the braking surfaces of the brake discs of vehicles are known. One such is that disclosed for example in US7097006, which itself references a large number of groove arrangements.

[0003] Groove segments are aids, in heat dissipation, stress relief and vibration reduction, and need to be tailored to the particular characteristics and construction of the disc to which they are applied.

[0004] A difficulty has been to derive a pattern of groove segments which meets these requirements but is also effective in a disc rotating in either clockwise or anticlockwise directions so that the disc may be used on either side of a vehicle and provide balanced and equal braking performances regardless of the direction of rotation.

[0005] Furthermore, the configuration of the actual machined slot has implications for both the performance of the brake pads applied to the disc surfaces and the integrity of the disc itself. Thus some known slot 25 configurations at least, have either a tendency to tearing

2017210670 07 Aug 2017 of the rotor surfaces or to cause hairline crack development at the brake band peripheries, or both.

[0006] Another problem with conventional brake discs is that there is no way a motorist can monitor the braking performance of the braking assembly of the vehicle. Braking efficiency and problems of incompatibility between brake pads and the brake bands of the disc can be indicated by the temperature of the discs after heavy braking, but this temperature can only be ascertained by use of sophisticated 10 thermal monitoring equipment.

[0007] It is an object of the present invention to address or at least ameliorate some of the above disadvantages.

Notes [0008] The term comprising (and grammatical variations thereof) is used in this specification in the inclusive sense of having or including, and not in the exclusive sense of consisting only of.

[0009] The above discussion of the prior art in the

Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country.

[0010] In this specification:

2017210670 07 Aug 2017

Arcuate groove means a groove following an arc of a circle or other geometrically defined curve.

Clockwise and anti-clockwise refer to rotational directions about the centre of a brake disc as viewed 5 from the outward side.

BRIEF DESCRIPTION OF INVENTION [0011] Accordingly, in a first broad form of the invention, there is provide a brake disc for a wheeled 10 vehicle; said brake disc including opposing annular braking surfaces; each of said surfaces provided with an identical pattern of disparate arcuate groove segments; said groove segments arranged in groups; each group including at least:

a pair	of	inner arcuate	groove	segments	extending
outwardly	from proximate	an inner circumferential
edge of	a	said brake band	surface	to proximate a mid
portion	of	the width of said brake	band,
a pair	of	outer arcuate	groove	segments	extending

outwardly from proximate a mid portion of the width of said brake band to proximate an outer circumferential edge of said brake band, and wherein said pair of inner arcuate groove segments and said pair of outer arcuate groove segments each include a clockwise arcing and an anticlockwise arcing groove 25 segment; said brake disc providing identical braking performance independent of direction of rotation.

2017210670 07 Aug 2017 [0012] Preferably, each of said opposing braking surfaces includes four of said groups of arcuate groove segments; each said group occupying a quadrant of said brake disc.

[0013] Preferably, respective said clockwise arcing groove segment and anticlockwise arcing groove segment of each of said pair of inner arcuate groove segments and said pair of outer arcuate groove segments are disposed symmetrically about respective radial lines of symmetry.

[0014] Preferably, said clockwise arcing groove segment of said pair of outer groove segments is located along an arc defining said clockwise arcing groove segment of said pair of inner arcuate groove segments; said outer groove segment separated from said inner groove segment by a gap.

[0015] Preferably, said of each said arcuate groove segments arcs outwardly convexly.

[0016] Preferably, said pattern includes a pair of intermediate arcuate groove segments; said pair of intermediate arcuate groove segments disposed symmetrically 20 about a radial line of symmetry.

[0017] Preferably, an anticlockwise arcing one of said pair of intermediate arcuate groove segments is located such that its midpoint lies on said arc defining said clockwise arcing groove segment of said pair of inner 25 arcuate groove segments and at a midpoint of said gap

2017210670 07 Aug 2017 separating said outer groove segment from said inner groove segment.

[0018] Preferably, a said radial line of symmetry of said pair of outer arcuate groove segments lies 5 approximately 15degrees advanced in a clockwise direction from a radial line of symmetry of said pair of inner arcuate groove segments.

[0019] Preferably, a said radial line of symmetry of said pair of outer arcuate groove segments lies 10 approximately SOdegrees advanced from a radial line of symmetry of said pair of inner arcuate groove segments.

[0020] Preferably, a said radial line of symmetry of said pair of intermediate arcuate groove segments lies approximately midway between said radial lines of symmetry 15 of said pair of inner arcuate line segments and said pair of outer arcuate line segments.

[0021] Preferably, said pair of inner arcuate groove segments is machined such that end portions of said groove segments adjacent an inner circumferential edge of said 20 brake band surface gradually increase in depth.

[0022] Preferably, said pair of outer arcuate groove segments is machined such that end portion of said groove segments adjacent an outer circumferential edge of said brake band surface gradually increase in depth.

2017210670 07 Aug 2017 [0023] Preferably, distal ends of said pairs of inner and outer arcuate groove segments are machined such that said grooves are at full depth at said distal ends.

[0024] Preferably, both ends of said intermediate pairs

5 of arcuate	groove	segments	are	machined	such that said
grooves are	at full	depth at	said	both	ends .
[0025] Preferably	, outer	rims	of	brake	bands forming

said opposing annular braking surfaces are provided with at least one set of colour markings; said colour markings 10 applied with thermally sensitive paints.

[0026] Preferably, said colour markings comprise stripes of said thermally sensitive paints extending from an edge of an inward facing said annular braking surface of an inner said brake band to an edge of an outward facing said 15 annular braking surface of an outer said brake band.

[0027] Preferably, said stripes are of distinct colours; each said distinct colour changing colour according to a predetermined elevated temperature band.

[0028] In another broad form of the invention, there is 20 provided a method of providing equal braking performance in a brake disc for a vehicle in both clockwise and anticlockwise rotation; said method including the steps of machining a repeating groove pattern in surfaces of opposing brake bands of said disc; each of said repeating 25 groove patterns including at least a pair of inner arcuate groove segments and a pair of outer arcuate groove

2017210670 07 Aug 2017 segments; a first arcuate groove segment of each said pair arcing towards a mid portion of a said brake band in a clockwise direction; a second arcuate groove segment of each said pair arcing to wards a mid portion of a said 5 brake band in an anticlockwise direction.

[0029] Preferably, ends of said inner and outer arcuate groove segments adjacent respective inner and outer peripheries of said brake band surfaces are machined so as to gradually reach full depth as machining proceeds away 10 from said inner and outer peripheries.

[0030] Preferably, distal ends of said inner and outer arcuate groove segments are machined such that said groove segments remain at said full depth at said distal ends.

[0031] In yet another broad form of the invention, there is provided a pattern of grooves provided in opposing annular brake band surfaces of a disc brake disc; said pattern comprising three sets of arcuate grooves arranged radially around each of said opposing brake band surfaces; each set of said three sets of arcuate grooves including four pairs of radially distributed arcuate grooves; grooves of each said pair of arcuate grooves extending symmetrically in clockwise and anticlockwise directions about a respective radial line of four radial lines of said set; said four radial lines defining four equal annular portions of said brake band surface.

2017210670 07 Aug 2017 [0032] Preferably, grooves of said first set arc convexly from an inner periphery of a said brake band to at least a mid portion of said brake band surface.

[0033] Preferably, said four radial lines for said second set of arcuate grooves are rotationally offset in a clockwise direction relative orientation of said four radial lines for said first set of arcuate grooves; said rotational offset approximately 30degrees; said offset such that each said arcuate groove of said second set lies 10 substantially on a continuation of an arc defined by a

corresponding arcuate groove of said	first	set.
[0034]	Preferably,	grooves	of	said	second set arc
convexly	from an outer periphery	of a	said brake band

towards respective outer ends of said arcuate grooves of 15 said first set; each respective outer end of an arcuate groove of said second set separated from a corresponding outer end of a corresponding arcuate groove of said first set by a gap.

[0035] Preferably, said four radial lines for said third 20 set of arcuate grooves are rotationally offset in an anticlockwise direction relative orientation of said four radial lines for said first set of arcuate grooves; said rotational offset approximately 30degrees; said offset such that each said arcuate groove of said third set extends 25 through said gap between outer ends of corresponding arcuate grooves of said first set and said second set;

midpoints of said arcuate grooves of said third set

2017210670 07 Aug 2017 proximate first set.

[0036] third set said arcs

Preferably, defined by arcuate each said arcuate arcs convexly from a first end grooves of groove of proximate a said said mid portion of said brake band surface to a second end towards an outer periphery of said brake band.

[0037] Preferably, said first ends of said arcuate grooves of said third set lie at a smaller radial distance 10 from a centre of said disc than a radial distance of outer ends of said arcuate grooves of said first set.

[0038] Preferably, said second ends of said arcuate grooves of said third set lie at a greater radial distance from said centre of said disc than a radial distance of 15 outer ends of said arcuate grooves of said second set.

[0039] In another broad form of the invention, there is provided a brake disc for a wheeled vehicle; said brake disc including opposing annular braking surfaces; each of said surfaces provided with an identical pattern of 20 disparate arcuate groove segments; said groove segments arranged in groups; each group including at least:

	(a)	a pair of inner	arcuate groove	segments
		extending outwardly	from	proximate	an	inner
		circumferential edge	of	a said brake	band
25		surface to proximate	a mid	portion of	the	width

of said brake band (b) a pair of outer arcuate groove segments extending outwardly from proximate a mid portion of the width of said brake band to proximate an

2017210670 07 Aug 2017 outer circumferential edge of and wherein said pair of inner arcuate groove said brake band, segments and said each include a pair of outer arcuate groove segments

clockwise	arcing and	an	anticlockwise	arcing
segment; said brake	disc	providing	identical 1
10 performance	independent	of	direction	of	rotation
brake disc	further provided	with at	least one

groove braking sensitive coloured markings temperature set of ; said at the periphery of said brake disc; respective ones of said coloured markings changing colour at a predetermined band of elevated

In yet a further broad form of the invention there is provided a method of arranging grooves in opposed brake band surfaces of a brake disc; said method comprising forming grooves on both sides of said brake disc; said grooves limited to a first and second set of grooves; the first set of grooves comprising arcuate grooves which extend from proximate an inner circumferential edge of said brake pad surface of said brake band to proximate a mid portion of the width of the brake band; said second set of grooves comprising arcuate grooves which extend from

2017210670 07 Aug 2017 proximate said mid portion of the width of said brake band to proximate an outer circumferential edge of said brake band; said grooves arced and paired whereby braking performance is substantially the same in use independent of 5 direction of rotation of said brake disc.

Preferably a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with a one of said arcuate grooves which extend from proximate 10 said mid portion.

Preferably said a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with said a one of said arcuate grooves which extend from proximate said mid portion and wherein the grooves thus paired are on the same side of the brake disc.

Preferably said a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with 20 said a one of said arcuate grooves which extend from proximate said mid portion and wherein the grooves thus paired are each on an opposite side of the brake disc.

Preferably the pattern of arcuate grooves are arranged as a 25 mirror image of each other on opposed sides of the brake disc.

2017210670 07 Aug 2017

BRIEF DESCRIPTION OF DRAWINGS [0040] Embodiments of the present invention will now be described with reference to the accompanying drawings 5 wherein:

Figure 1 is an orthogonal side view of one side a brake disc provided with patterns of arcuate groove segments according to a first preferred embodiment of the invention,

Figure 2 is a perspective view of the brake disc of

Figure 1,

Figure 3 is an orthogonal side view of one side of a brake disc provided with patterns of arcuate groove segments according to a second preferred embodiment of the 15 invention,

Figure 4 is a perspective view of the brake disc

Figure 3,

Figure 5 is a partial cross section of the brake disc of Figure 1 and Figure 3 showing the machining pattern of 20 groove segments adjacent the inner peripheries of the brake band surfaces,

Figure 6 is a partial cross section of the brake disc of Figure 1 and Figure 3 showing the machining pattern of groove segments adjacent the outer periphery of the brake 25 band surfaces and groove segments at an intermediate position.

2017210670 07 Aug 2017

Figure 7 is a view of a first set of groove segments forming a part of the groove pattern of the second preferred embodiment of the invention,

Figure 8 is a view of a second set of groove segments forming a part of the groove pattern of the second preferred embodiment of the invention,

Figure 9 is a view of a third set of groove segments forming a part of the groove pattern of the second preferred embodiment of the invention,

Figure 10 shows the complete pattern of groove segments according to the second preferred embodiment of the invention as formed by the combination of the sets of groove segments of Figures 7 to 9,

Figure 11 is a general perspective view of brake disc according to the invention showing thermal indicating markings on outer rims of the brake bands of the brake discs in a further preferred embodiment of the invention,

Figure 12 is an enlarged view of a set of the thermal markings of Figure 11,

Figure 13 is a side view of a fourth preferred embodiment of sets of groove patterns.

2017210670 07 Aug 2017

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Preferred Embodiment [0041] With reference to Figures 1 and 2, a brake disc comprises opposing annular brake bands 12 and 14 supported by a central hub 16. Brake bands 12 and 14 may form the outer surfaces of a solid disc or, as shown in

Figure 2, comprise two discs interconnected by arrays of pillars 18 which allow air flow between the brake bands, as well known in the art.

[0042] Each outer surface 20 and 22 of the brake bands and 14 is provided with groups 24 of arcuate groove segments 26, machined into the respective outer surfaces.

Preferably, the groove segments 26 are approximately 3mm in width with a depth of approximately 1.5mm.

[0043] The following description refers to the surface of brake band 12 as shown in Figure 1, but it will be understood that the identical arrangement of groove segments is applied to the surface 22 of the opposite brake band 14. Preferably the patterns on the two opposing sides 20 are rotationally offset by 30degrees.

[0044] Each group 24 of arcuate groove segments 26 of this preferred embodiment of the invention, comprises arcuate groove segments oriented in both clockwise and anti-clockwise directions. The groups are four in number 25 and occupy 90degree quadrants of the brake band surface 20.

[0045] Each group includes one pair of inner arcuate

2017210670 07 Aug 2017 groove segments 27 and 28, extending outwardly from proximate the inner circumferential edge 30 of the brake band surface 20, across approximately three quarters of the width, or at least past the mid portion, of the brake band.

Groove segments 27 and 28 are disposed about a radial line of symmetry 32, and arc convexly in opposing clockwise and anticlockwise directions, with their inner termini 34 and 36 adjacent the radial line of symmetry 32.

[004 6] Each of the groove segments 27 and 28 is associated with one of a pair of outer shorter arcuate groove segments, 38 and 40 respectively. The first of these, shorter groove segment 38, extends outwardly from proximate the mid portion of the width of the brake band surface 20 and arcs, also convexly, in a clockwise direction to a point at the periphery 42 of the brake band surface 20, and proximate the radial line of symmetry 32 of groove segments 27 and 28.

[0047] The second shorter groove segment 40 is equal in extent to the first shorter groove segment 38, but arcs convexly in the opposite anticlockwise direction. The two shorter groove segments 38 and 40 are symmetrical about a radial line of symmetry 44 advanced approximately 15degrees in a clockwise direction from the radial· line of symmetry 32 of the pair of inner groove segments 27 and 28.

[0048] This pattern of groove segments 26 is repeated for each quadrant of the brake bands 12 and 14.

2017210670 07 Aug 2017

Second Preferred Embodiment [0049] In a second preferred embodiment of the invention and with reference now to Figures 3 and 4, a similar brake disc 200 as previously described above is similarly provided with an arrangement of groove segments 226, identical on each opposing brake band 212 and 214.

[0050] The groove segments 226 are arranged also in four repeating groups 224 of groove segments; each group 224 thus occupying a 90degree quadrant of a brake band surface

220 and 222. For convenience of description, each quadrant may be divided into three sectors of approximately 30degrees. Each group 224 Includes a pair of innermost groove segments 227 and 228 disposed symmetrically about a 15 first 30degree radial line of symmetry 232, and have their inner termini 234 and 236 adjacent the inner circumferential edge 230 of the brake band. These inner groove segments extend outwardly, convexly clockwise and anticlockwise respectively, to approximately three quarters 20 of the width of the brake band surface 220.

[0051] In this embodiment, the pattern also includes a pair of clockwise and anticlockwise outer groove segments 238 and 240 respectively, symmetrical about the second 30degree radial line of symmetry 244. The preferred 25 arrangement is such that the first of these outer groove segments, the clockwise groove segment 238, lies on the arc

2017210670 07 Aug 2017 of clockwise inner groove segment 227, being separated from the distal· end of that groove segment by a gap 235. Each of these outer groove segments 238 and 240 extends approximately the outer one third of the width of the brake 5 band, with their distal termini proximate the outer periphery 242 of the brake band surface 220.

[0052] Each quadrant 224 includes one further pair of clockwise and anticlockwise intermediate groove segments 246 and 248 respectively. Intermediate groove segments 246 10 and 248 are disposed symmetrically about a radial line of symmetry 250 lying approximately midway between the lines of symmetry 232 and 244 of the pairs of inner and outer groove segments respectively. The arrangement is such that the anticlockwise intermediate groove segment 246 passes 15 through the gap 235 and such that its midpoint lies on the arc defining the previously described inner groove segment 227 and outer groove segment 238.

[0053] It can be seen that each of the embodiments described above provides for an equal number and total 20 lengths of clockwise and anticlockwise arcuate groove segments on each brake band of the brake disc. This allows the discs to be equally effective in braking regardless of the direction of rotation of the disc.

[0054] The pattern of arcuate grooves of this second 25 embodiment, may alternatively be described as a combination of the patterns of three sets of grooves. With reference to

Figures Ί to 9, each of the three sets can be described with reference to four radial lines (100, 102, 104 and 106)

2017210670 07 Aug 2017

(with	specific relative orientation	for	each	set)	which
define	four	equal	annular portions	of	the	brake band
surface (120) ;	that	is adjoining pairs	of	these	four	radial
lines	subtend	right	angles .
[0055]	Each	of	the three sets	of	arcuate	grooves

comprises four pairs of grooves, in which each pair comprises a clockwise groove and an anticlockwise groove 10 arranged symmetrically about a radial line.

[0056] With reference now to Figures 7 and 10, in the first set of the three sets of arcuate grooves, each pair of arcuate grooves (127, 128) arc convexly (clockwise and anticlockwise) from proximate an inner periphery (130) of 15 the brake band to outer ends (135, 137), somewhat past a mid portion of the brake band surface (120).

[0057] As can be seen in Figures 8 and 10, the four radial lines for the second set of pairs of arcuate grooves (138, 139) are rotationally offset in a clockwise direction 20 relative the orientation of the four radial lines for the first set of arcuate grooves. This rotational offset is approximately 28degrees, and is such that each clockwise arcuate groove of this second set lies substantially on a continuation of an arc defined by a corresponding clockwise 25 arcuate groove of the first set, as can be seen in Figures and 10.

2017210670 07 Aug 2017 [0058] The pairs of arcuate grooves (138, 139) of the second set arc convexly from proximate the outer periphery (142) of the brake band, towards the respective outer ends (135, 137) of the arcuate grooves (127, 128) of the first set. The respective outer ends (151, 153) of the arcuate grooves (138, 139) of this second set are separated from the corresponding outer ends (135, 137) of the first set by gaps (135) as can be seen in Figures 3 and 10.

[0059] With reference now to Figures 9 and 10, the four radial lines (100, 102, 104 and 106) for the third set of pairs of arcuate grooves (146, 148) are rotationally offset in an anticlockwise direction relative to their original orientation for the first set of arcuate grooves (127, 128) as shown in Figure 7. In this case the rotational offset is 15 approximately 28degrees, with the offset such that each of the anticlockwise arcuate groove of the pair of grooves (146, 148) of this third set extends through a gap (135) between the outer ends of corresponding arcuate grooves of the first set (127, 128) and the second set (138, 139). The 20 midpoints of these arcuate grooves (146, 148) of the third set lie approximately on the arcs defined by the arcuate grooves (127, 128) of the first set. Each pair of arcuate

grooves (146, 148) of	the third	set arcs convexly	from
first	ends (155, 157)	proximate	a mid	portion of	said
25 brake	band surface, to	second ends	(161,	163) towards	the

outer periphery (242) of the brake band.

2017210670 07 Aug 2017 [0060] Figure 10 shows the three sets of arcuate grooves combined now to form the complete pattern of grooves on the brake band surface.

[0061] It can be seen that the grooves of the three sets are arranged so that there is at least some overlap of the grooves. That is, there is no annular band of the surface of the brake bands which is not interrupted by the grooves of at least one of the sets of grooves. Thus the first ends (155, 157) of the arcuate grooves of the third set lie at a 10 smaller radial distance from the centre of the disc than

the radial distance	of outer	ends	(135,	137)	of the	arcuate
grooves	(127, 128)	of said	first	set,	so that these	ends
overlap	radially.
[0062]	Similarly,	the second	ends	(161,	163)	of	the

arcuate grooves (146, 148) of the third set, lie at a greater radial distance from the centre of the disc than the radial distance of the outer ends (151, 153) of the arcuate grooves (138, 139) of the second set, again providing an overlap.

Third Preferred Embodiment [0063] In a further preferred embodiment according to the invention, the brake rotor brake bands and grooving conforms to the that described in either of the above first and second embodiments. In this preferred embodiment 25 however, the outer rims (300, 302) of the brake bands are

2017210670 07 Aug 2017 provided with at least one set (304) of colour markings as indicated in Figure 10.

[0064] Preferably, each set (304) of the at least one set, comprises a painted stripe extending transversely from the edge of the outward facing surface of the outer brake band (302) to the edge of the inward facing surface of the inner brake band (300).

[0065] Preferably also, the sets (304) of colour markings are regularly arranged around the circumference of the brake disc and are sufficient in number such that at least one set will be visible to an observer regardless of the position the brake disc has assumed when the vehicle to which it is fitted has come to rest.

[0066] In a preferred arrangement as shown in Figure 12, each set (304) is comprised of three spaced apart painted stripes (306), (308) and ¢310). The colours are distinct one from the other so as to be readily distinguishable and are preferably green, orange and red with all the sets repeating the pattern of colours in the same order.

[0067] The paints used for the stripes (306,308,310) are thermally sensitive paints which react to elevated temperatures in the metal to which they have been applied and react by changing to different colours when the temperature of the supporting surface reaches predetermined elevated temperature bands .

2017210670 07 Aug 2017 [0068] Preferably, in the present embodiment of the invention, the green paint of stripe (306) changes to white in the temperature band of 458°C to 856°C, the orange stripe (308) changes to yellow between 550°C and 1022°C, 5 while the red stripe (310) also changes to white between 630°C and 1166°C.

[0070] The brake disc of the present embodiment is supplied together with a colour interpretation chart (not shown) so that the vehicle owner or operator can refer to 10 the chart and compare the current colour of the stripes with that of the chart. The chart may additionally contain information as to possible interpretations of the current colour of a disc under different braking conditions as an aid to assessing braking performance.

Fourth Preferred Embodiment [0071] With reference now to Figure 13, in this embodiment, a brake disc 400 is again provided with machined arcuate grooves 426,434 on each brake band surface 412, which are a subset of the grooves of Figure 1. The 20 arcuate grooves 426,434 in this instance comprise solely of a number of both inner arcuate grooves 426 and outer arcuate grooves 434 spaced at regular intervals around the brake bands. The grooves may be considered as arranged in pairs, made up of an inner arcuate groove and an outer 25 arcuate groove, preferably as shown in Figure 13, six pairs.

2017210670 07 Aug 2017 [0072] Each of the inner arcuate grooves extends outwardly from proximate an inner periphery of the brake band to terminate proximate a mid portion of the brake band, while each of the outer arcuate grooves extends 5 outwardly from a mid portion of the brake band surface 412 terminating at or proximate to the periphery 442 of the brake band surface. None of the grooves extends across the width of the brake band.

[0073] In the preferred arrangement, as can be seen in 10 Figure 11, all the grooves 426,434 arc in a concave manner relative the inner periphery 430 of the brake band surface, with set of inner arcuate grooves 426 and the set of outer arcuate grooves 434 arcing in opposite anti-clockwise and clockwise directions.

[0074] It can be seen from Figure 13 that in a preferred arrangement, the pair of one inner arcuate groove and one outer arcuate groove, are arranged such that an extension of the centre line of the inner arcuate groove would intersect the centre line of the outer arcuate groove approximately at the mid point of the outer arcuate groove.

[0075] The pattern of inner and outer arcuate grooves is identical on both sides of the brake disc, so that if the disc shown in Figure 11 were rotated 180degrees about a diameter, the pattern of grooves then displayed would be 25 identical. Thus it is clear that the braking performance of

2017210670 07 Aug 2017 the groove patterns of this embodiment is identical regardless of the direction of rotation.

Groove Machining [007 6] In each of the above embodiments, the arcuate groove segments are machined in a particular way. Typically grooves machined in disc surfaces are introduced into the disc material by a gradual plunging of the ball cutter tool as it is moves along the trajectory of the groove path, and exits in a similar way by gradually retracting the tool tip 10 as it approaches the end of the groove path.

[0077] In grooves which end at some intermediate point on the disc brake band, that is in the area of maximum applied force by the brake callipers, such feathered groove ends tend to react adversely with the brake pad, in some cases 15 causing a tearing of the disc material. Nevertheless, feathered or gradually produced groove ends are advantageous for those groove ends close to either the outer or inner peripheries of the brake band, in that they reduce the possibility of hair line fractures developing 20 between the groove end and the disc periphery. These areas close to the inner and outer peripheries of the brake band surface are in any case not swept by the brake pads.

[0078] It can be seen, particularly in Figures 5 and 6, that the grooves of the present invention retain the 25 advantages of feathered ends 50 of groove ends at both the inner periphery 30 and the outer periphery 42 (in Figure 1)

2017210670 07 Aug 2017 and feathered ends 254 of groove ends at both the inner and outer peripheries 230 and 242 (in Figure 3) . However the distal ends (52 and 252 respectively) of these grooves are not feathered. Nor are both ends of the intermediate 5 grooves 246 and 248 so feathered.

[0079] In both embodiments of the invention, the preferred machining method for groove ends adjacent to the brake band surface peripheries, is to gradually introduce the tool tip (preferably an 80degree 5mm ball cutter) into 10 the disc material as the tool moves away from the periphery along the groove path until the required depth is reached, then machine in towards the middle portion of the brake band. When the distal end of the groove path is reached, tool motion parallel to the disc surface is arrested and 15 the tool withdrawn from the groove. Preferably, the ball cutter is plunged into the disc surface to a maximum depth at which the groove width at the surface is 3mm.

[0080] The grooves machined in this way thus have full groove depth substantially up to the ends (52/252) of the 20 grooves in the middle portion of the brake bands, and tests have indicated that this groove end configuration eliminates the problem of disc material tearing. At the same time the method retains the advantages associated with a feathered groove end configuration at the brake band 25 peripheries.

2017210670 07 Aug 2017 [0081] In the case of the Second Preferred Embodiment, the pair of intermediate arcuate groove segments 246 and 248 are machined such that the grooves are of the same depth throughout. These groove segments are machined by plunging the tool tip to the full depth of the groove at the start of the groove and retracting the tool tip at the end of the groove after the tool tip motion parallel to the brake surface has been arrested.

[0082] Test have further shown that the arrangement of groove segments described in each of the embodiments, provides for excellent braking performance as well as providing the major benefit of equal performance regardless of direction of rotation.

[0083] The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims (13)

1. A pattern of grooves machined into each opposing surface of brake bands of a brake disc; said grooves limited to a set of inner arcuate grooves and a set of outer

5 arcuate grooves; said inner arcuate grooves extending outwardly from an inner circumferential edge of said brake band surface to proximate a mid portion of the brake band surface; said outer arcuate grooves extending outwardly from proximate said mid portion of

10 the brake band surface to an outer circumferential edge of the brake band surface; said pattern providing equal braking performance independent of direction of rotation.

2. The pattern of grooves of claim 1 wherein said inner

15 arcuate grooves and said outer arcuate grooves are arranged in pairs of grooves spaced around said brake band surface.

3. The pattern of grooves of claim 1 or 2 wherein each of said inner arcuate grooves and said outer arcuate

20 grooves arc concavely relative said inner circumferential edge.

4. The pattern of grooves of claim 3 wherein said pairs are six in number.

5. The pattern of grooves according to claim 3 or 4 wherein

25 the inner arcuate groove and the outer arcuate groove

-28 2017210670 06 Aug 2019 of each of said pairs of grooves are arranged such that an extension of the centre line of the inner arcuate groove would intersect the centre line of the outer arcuate groove approximately at the mid point of the 5 outer arcuate groove.

6. The pattern of grooves according to any one of claims

1 to 5 wherein outer rims of brake bands forming said opposing brake band surfaces are provided with at least one set of colour markings; said colour markings applied 10 with thermally sensitive paints.

7. The pattern of grooves of claim 6 wherein said colour markings comprise stripes of said thermally sensitive paints extending from an edge of an inward facing said brake band surface of an inner said brake band to an

15 edge of an outward facing said brake band surface of an outer said brake band.

8. The pattern of grooves of claim 7 wherein said stripes are of distinct colours; each said distinct colour changing colour according to a predetermined elevated

20 temperature band.

9. A method of arranging grooves in opposed brake band surfaces of a brake disc; said method comprising forming grooves on both sides of said brake disc; said grooves limited to a first and second set of grooves; the first

25 set of grooves comprising arcuate grooves which extend

-292017210670 06 Aug 2019 from proximate an inner circumferential edge of said brake pad surface of said brake band to proximate a mid portion of the width of the brake band; said second set of grooves comprising arcuate grooves which extend from

5 proximate said mid portion of the width of said brake band to proximate an outer circumferential edge of said brake band; said grooves arced and paired whereby braking performance is substantially the same in use independent of direction of rotation of said brake disc.

10 10. The method of claim 9 wherein a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with a one of said arcuate grooves which extend from proximate said mid portion.

15

11. The method of claim 10 wherein said a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with said a one of said arcuate grooves which extend from proximate said mid portion and wherein the grooves thus paired are on the

20 same side of the brake disc.

12. The method of claim 10 wherein said a one of the arcuate grooves which extend from proximate an inner circumferential edge is paired with said a one of said arcuate grooves which extend from proximate said mid

-302017210670 06 Aug 2019 portion and wherein the grooves thus paired are each on an opposite side of the brake disc.

13. The method of any one of claims 9 to 12 wherein the pattern of arcuate grooves are arranged as a mirror 5 image of each other on opposed sides of the brake disc.