GB2434624A

GB2434624A - Brake pad arrangement for a disc brake

Info

Publication number: GB2434624A
Application number: GB0601686A
Authority: GB
Inventors: Glynn Ashman; Alan Terence Bowler
Original assignee: TRW Ltd
Current assignee: TRW Ltd
Priority date: 2006-01-27
Filing date: 2006-01-27
Publication date: 2007-08-01
Also published as: GB0601686D0

Abstract

A brake pad arrangement 2 for a disc brake comprising a carrier 4, a first brake pad 14 being mountable in the carrier by being introduced along a radial plane, the cater having a pair of axial projections 16,17 coupled to the carrier, and a second brake pad 24 being shaped to receive and embrace/encircle the mounting projections and thereby be mounted thereon. Ideally, a shoulder formed on first brake pad engages a recess in the carrier when said first pad is rotated to be mounted in place. The mounting projections are preferably pins 16,17 while the second brake pad preferably comprises through bores. A calliper 34 is ideally mounted on the brake pad arrangement. A spring may be provided to reduce rattle. Other independent claims relate to a torque plate having two openings for receiving projecting pins, a backing plate for a brake pad, and a brake pad which is mounted by rotating it into a carrier.

Description

DESCRIPTION

DISC BRAKE

The present invention is concerned with disc brakes.

Disc brakes are well known and very widely used in motor vehicles. The braking effect is provided by means of a pair of friction pads urged against opposite faces of the brake disc. A single actuator is commonly used to apply the required force to both brake pads. The actuator is mounted on a movable caliper body, which bridges the two brake pads. The actuator acts directly on one of the pads and its force is reacted through the movable caliper body to the other of the pads. In this way the pads are drawn against the respective faces of the brake disc. Other, generally more expensive, brakes have an actuator for each brake pad.

Torque exerted by the disc upon the pads, tending to cause them to move circumferentially along with the brake disc during braking, must be reacted to some fixed structure. The torque may be reacted through the caliper body itself Commonly, the caliper body is slidably mounted on a pair of pins attached to a carrier. The brake pads are located by engagement with the caliper body, and torque is borne by the carrier Alternatively, the brake pads may be mounted directly in the carrier. Lucas Industries' European patent 0752541 (application 96305012.5) shows one such arrangement, in which the brake pads are located in a fixed torque plate which locates them against movement along the circumferential direction but permits them to move along their intended direction of travel, generally parallel to the brake disc's axis.

Another example is provided by UK patent 943838, granted to Societe Anonyme DBA, which concerns a brake having a pad support which is fixedly mounted on an axle through a hub from which it extends first radially outwardly, being branched to provide a pair of arms between which a first brake pad is mounted, and then axially, to traverse the brake disc, and finally radially inwardly, to form another pair of arms between which the second brake pad is mounted on the opposite side from the first.

Each brake pad is radially located by means of a respective pair of angle pieces screwed to the support. The support itself is an intricately shaped component whose cost of manufacture would have been significant Since motor vehicle brakes are typically mass-produced and cost sensitive, it is desirable that the means used to mount the brake pads, and the brake as a whole, should be simple to manufacture and have a low parts count. Nonetheless the pad's mounting is safety critical and is required to be positive and secure.

Brake pads are subject to wear and require periodic replacement It is desirable that this process should be as simple and rapid as possible. Removal and replacement of brake pads typically involves partial disassembly of the brake. For example the caliper body must normally be removed to provide access to the pads themselves. It is desirable that this process should be rapid and straightforward In accordance with a first aspect of the present invention, there is a brake pad arrangement for a disc brake, the arrangement comprising a carrier, a first brake pad, and a second brake pad, the carrier being adapted to be fixedly mounted on one side of a brake disc defining an axis, and being shaped to provide a cradle which is radially open, enabling the first brake pad to be introduced to the cradle by moving it along a radial plane and thereby to be axially movably mounted, the cradle providing opposed abutment surfaces by which the first brake pad is circumferentially located, the arrangement further comprising a pair of axial mounting projections fixedly coupled to the carrier, the second brake pad being shaped to receive and embrace the mounting projections and thereby to be axially movably mounted on the other side of the brake disc, the projections serving to locate the second brake disc both circumferentially and radially.

The brake pad arrangement thus provides a constructionally simple way to mount both pads and to provide for the braking torque to be referred to the fixed carrier in principle the brake pads could each be formed by a friction pad alone, but in practice each will more usually comprise a friction pad carried upon a shaped back plate Preferably, the second brake pad has through-going bores which receive the respective mounting projections. However other formations would in principle be suitable, provided they achieve the required engagement with the axial projections.

Preferably, the carrier is formed as a shaped plate and the mounting projections are formed as pins mounted in the plate.

It is particularly preferred that the cradle is formed by a pair of radially outwardly extending limbs between which the first brake pad is received.

Preferably, the carrier has an undercut and the inboard brake pad has a shoulder formed to engage with the undercut and thereby to be radially located This provides a simple but positive means of radially locating at least part of the brake pad Preferably, the fonnation of the inboard pad and the carrier part is such that to engage them requires the inboard pad to be advanced to introduce the shoulder to the undercut, and then to be rotated to seat the inboard pad upon the carrier. In order to lock the pad in position it is then merely necessary to provide a retainer for rotationally locating the first brake pad and so retaining it upon the carrier, the retainer being releasable by a user. It may be formed as a spring clip.

The arrangement is preferably incorporated in a disc brake further comprising a caliper body which carries an actuator for applying a force to one of the brake pads and which engages with the other of the brake pads to react the force to it, wherein the caliper body is axially movably mounted by engagement with the brake pads. This engagement may of course, in the case of one of the pads, be through the actuator. It is particularly preferred that the coupling of the caliper body to the pads provides its sole means of mounting.

The caliper body preferably engages with at least one of the brake pads through inter-fitting male and female engagement features introducible to each other along the axial direction, and is such that disengaging these parts requires de-mounting of at least one of the brake pads. Hence the caliper body is captive until one of the brake pads is released It is particularly preferred that the male engagement feature(s) are formed as semi-shears in a back plate of the brake pad This is highly economical in manufacture.

According to a second aspect of the present invention, there is a torque plate for a disc brake which is adapted to be fixedly mounted alongside a brake disc having an axis and which is shaped to define a cradle for receiving a first brake pad, the cradle providing opposed abutment surfaces for circumferentially locating the first brake pad and being radially open to enable it to receive the first brake pad along a radial direction, the torque plate having two openings for receiving and mounting axially projecting pins for mounting a second brake pad.

According to a third aspect of the present invention, there is a back plate for a brake pad, formed as a shaped metal plate having a first face for carrying a pad of friction material and a second face opposite the first for engaging with a device for applying a braking force, the second face having projections for locating the brake pad relative to the aforesaid device and the projections being formed as semi-shears.

In accordance with a fourth aspect of the present invention, there is an assembly for use in a disc brake, comprising a carrier adapted to be fixedly mounted adjacent a brake disc and a brake pad adapted to seat upon the carrier and so to be mounted by it such as to be movable along an axial direction, the carrier having opposed surfaces which, by abutment with the brake pad, serve to circumferentially locate it, wherein the carrier has an undercut and the brake pad has a complementarily formed shoulder, the formation of the carrier and the brake pad enabling the brake pad to be installed by inclining it to its mounted orientation and advancing it along a direction in a radial plane to introduce the shoulder to the undercut, then rotating the brake pad to seat it upon the carrier, causing the shoulder to be trapped by the undercut so that the brake pad cannot subsequently be withdrawn along the radial plane without rotating it.

In principle the brake pad could be formed by a friction pad alone, but typically the brake pad itself is mounted on a back plate and it is the back plate which engages with the carrier In a preferred embodiment the carrier comprises a pair of radially outwardly extending limbs between which the brake pad is received. The undercut is preferably formed on one of the limbs, the other limb having a seating surface to which the brake pad is introducible by the aforesaid rotation. The carrier may take the form of a torque plate The axial direction along which the pad is movable is then perpendicular to the plane of the plate.

To maintain the brake pad in its seated position it is merely necessary to prevent it from rotating A preferred embodiment further comprises a retainer for rotationally locating the brake pad and so retaining it upon the carrier, the retainer being releasable by a user. This may take the form of a spring clip. The clip may be adapted to be inserted and removed by the user to engage/disengage it, but the possibility then arises that it will be lost while e.g. replacing the pad. In a preferred embodiment the spring clip is mountable on one of the brake pad and the carrier such as to engage automatically when the brake pad is seated upon the carrier. In one such embodiment one of the brake pad and the carrier carries the spring clip and the other is shaped to provide a ramp surface along which the spring clip rides as the brake pad is rotated to seat it upon the carrier, the inclination of the ramp surface being such that the spring clip is thereby stressed, and the ramp surface leading to a recess, so that when the brake pad reaches its seated position the spring clip engages in the recess In motor vehicle applications it is important to minimise creation of unwanted noise. Two potential sources of noise are rattle due to loose brake parts and "clunk", created when backlash in the brake is taken up when changing from forward to reverse brake operation, or vice versa. The brake pad mountings typically incorporate some clearance and can be subject to both types of noise It is known to apply spring biasing to the brake pad to take up the backlash and so reduce noise, but again it is desirable to achieve this in a constructionally simple manner which involves a low parts count and is consistent with easy pad replacement.

This is achieved in accordance with certain embodiments of the present invention by using the spring clip by which the brake pad is retained to additionally bias the pad and so take up backlash in its mountings In principle the brake pad can move both radially and circumferentially in its mountings. In a particularly preferred embodiment, the spring clip circumferentially biases the brake pad toward convergent mating surfaces of the carrier, thereby taking up both circumferential and radial backlash in this region. The convergent mating surfaces are preferably part of the aforementioned undercut Additionally or alternatively the spring clip may serve to radially bias the brake pad. In a particularly preferred embodiment the spring clip comprises two sprung tongues which are inclined to each other and respectively serve to bias the brake pad radially and circumferentially. The forces created by the tongues need not be precisely radial and circumferential, but need simply have a component in these directions In an alternative embodiment, the spring clip comprises a resilient pin receivable by aligned, complementarily shaped recesses of the brake pad and the carrier.

A particularly preferred embodiment of the present invention comprises a caliper body and an arrangement for coupling the caliper body to the brake pad. The caliper body is preferably adapted to be mounted solely by virtue of its coupling to the brake pad, or to two brake pads. By virtue of the positive mounting of the brake pad and the coupling of the caliper body to it, other means for mounting the caliper body can be dispensed with. This is highly advantageous with regard to ease of maintenance and simplicity of construction. For example a sub-assembly comprising the pad and the caliper body may be mountable and dismountable simply by engaging/disengaging the pad.

The circumferential forces upon the brake pads need not be borne by the caliper body, so the coupling between the caliper body and the brake pad need not be heavy duty In a preferred embodiment one of the brake pad and the caliper body carries a coupling clip, the other being shaped to receive the coupling clip to couple the caliper body to the brake pad. Preferably the coupling of the brake pad to the caliper body is through an actuator carried by the caliper body, the brake pad being coupled to a movable part of the actuator. Thus for example the actuator may carry the cylinder part of a hydraulic actuator, the brake pad being coupled to a piston received in the cylinder In a ftirther preferred embodiment the carrier has at least one axially extending guide, the second brake pad slidably engaging with the guide and so being circumferentially located. Still more preferably the assembly comprises a pair of axially extending guides formed as pins projecting from the carrier and received by openings in the second brake pad Preferably the second brake pad and the caliper body carries a second coupling clip, the other being shaped to receive the second coupling clip to couple the caliper body to the second brake pad.

In accordance with a fifth aspect of the present invention, there is a brake pad for use in an assembly of the type already described, comprising a friction pad secured to a back plate, the back plate being shaped to provide the aforementioned shoulder Preferably the arrangement further comprises a coupling clip secured to the back plate for coupling the back plate to a caliper body A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which-Figure 1 is an exploded view of a caliper brake embodying the present invention; Figure 2 is a perspective illustration of the caliper body of the same brake and its inboard pad assembly, part of the caliper body being omitted for the sake of clarity, Figure 3 is a perspective illustration of a torque-plate and outboard pad assembly of the brake, Figure 4 is a perspective illustration of the assembled brake; Figure 5 is a rear elevation showing a step in the process of its assembly; Figure 6 is a front elevation showing the brake in situ; Figure 7 is a rear elevation again showing the brake in situ and including a first form of locating spring; Figure 8 is a perspective illustration of the locating spring, Figure 9 is a perspective illustration of an alternative form of the locating spring; Figure 10 is a rear view of the brake showing a stage in the process of its assembly and including a fl.irther form of locating spring; Figure 11 is an enlarged, perspective illustration of the locating spring and adjacent parts, Figure 12 is a plan view of a torque plate of the brake; Figure 13 is a front elevation of a brake pad and carrier according to a further embodiment of the invention, Figure 14 is a perspective view of a brake pad and piston of the further embodiment; Figure IS is a perspective view of the carrier and both brake pads of the further embodiment, and Figure 16 is a perspective view of an inboard brake pad for use in the brake.

The general construction of a brake 2 embodying the present invention can be I0 appreciated from Figure 1 The brake is to be fixedly mounted on a motor vehicle through a carrier in the form of a torque plate 4, which has through-holes 6 to receive mounting bolts (not shown) for this purpose. The torque plate 4 has a roughly sU shaped cut-away forming upstanding limbs 8, 10 which are circumferentially spaced and which embrace and locate an inboard brake pad comprising an inboard back plate 2 carrying an inboard friction pad 14. A parallel pair of guide pins 16, 17 are received in respective bores 18,20 in upper parts of these two limbs and in this way are rigidly mounted. The pins may for example be screwed into their bores, but in the present embodiment they are a firm push fit They provide a sliding mounting for an outboard brake pad comprising an outboard back plate 22 carrying an outboard friction pad 24. To this end the outboard back plate 22 has through-going bores 26,28 which receive respective grommets 30,3 2. The grommets receive the guide pins 16, I 7 as a sliding fit (see Figure 3). The braking load is not equally shared between the pins. Instead the bores are sized such that load is initially borne by one of the pins.

Only under higher loads is there sufficient deformation for load to be shared byboth.

A caliper body is seen at 34 and is in this embodiment a unitary casting, although other forms of construction could in principle be used. On its inboard side the caliper body 34 carries an integrally formed cylinder, produced by machining of the casting in this embodiment, whose open end can just be seen in Figure 1 at 36.

The opposite end of this cylinder is closed and porting within the caliper body (not shown in the drawings, but comprising a bore leading to the cylinder) is provided for application of hydraulic pressure A broad transverse limb 38, which is cut away at 40, spans the brake disc (which is not shown) and is turned downwards at its outboard end to form an ii abutment 42 which lies outboard of the outboard pad assembly 22,24 and abuts against it to transfer the braking force to the outboard brake pad 24 A coupling in the form of a clip arrangement serves to couple the outboard pad assembly 22,24 to the caliper body's abutment 42. This could in principle take any number of different forms, but in the present embodiment a first sheet metal clip 44 is used. It has three arms 46a-c at 900 intervals, each arm terminating in an outwardly curved return 48.

The abutment is cut away at 50 to receive the arms of the spring clip, and one of three shallow recesses in the periphery of the cutaway, to receive and locate the three arms, can be seen at 54. The spring clip 44 snaps into place with the returns 48 against the abutments outboard face to keep the parts together A piston 56 is shown outside its cylinder 36 in Figure 1, but is of course received as a sliding but sealed fit in the cylinder in the assembled brake The piston's outboard end abuts against the inboard back plate 12 and these parts are held together by another coupling formed as a clip arrangement This comprises a second spring clip 58, formed identically to the first in this embodiment, whose arms 60 are introduced into a bore 62 in the piston's outboard end, their returns locating upon an undercut shoulder 64 within the bore. Hence the inboard brake pad 14 and its back plate 12 are coupled to the caliper body 34 through the actuator formed by the piston 56 and cylinder 36.

Figure 5 shows in more detail the shape of the torque plate 4 and the inboard back plate 12. The terms left" and "right" are used for brevity and refer to the orientation of the brake seen in Figures 5 and 12 Left and right hand extremities of the back plate 12 are formed as shaped lugs 65,66. In the assembled brake these seat upon respective mating regions 68, 70 formed upon the left and right hand limbs 8,10 of the torque plate 4. The mating region 68 on the left hand limb 8 is formed as an undercut. When the lug 65 is seated in it, the shape of the undercut 68 is such that the lug cannot be disengaged merely by withdrawing it along the radial direction. This is prevented by a retaining surface 72 (see Figure 12 in particular) which faces generally radially inwardly to engage and retain the lug 65. The retaining surface contacts a shoulder 71 of the lug 65. Note also that the mating regions 68, 70 are such as to locate the back plate 12 along the circumferential direction, indicated by arrows 73 in Figure 5 The right hand mating region 70 has a circumferentially facing abutment surface 74 which abuts end face 75 of the right hand lug 66 to restrict rightward movement of the back plate 12. The abutment surface 74 leads to a seating surface 76 which is inclined but faces radially outwardly to define the radial position of the right hand lug 66, by abutment with a complementarily inclined seating surface 77 formed on the lug. The left hand mating region or undercut 68 could take any number of different shapes but in this particular embodiment it contacts the left hand lug 65 through the retaining surface 72 and a seating surface 78, these two surfaces converging with each other along the circumferential direction so that they form a "V" shape, albeit one with a flat bottom at 79. The left hand lug 65 has a correspondingly "V' shaped nose which, once inserted into the undercut 70, is prevented from moving rightward by abutment with it and is also located radially.

Note that while the right hand lug 66 is seated on its mating region 70, it is impossible to withdraw the left hand lug 65 from engagement with the torque plate 4.

To withdraw this lug, the back plate 12 must first be rotated, as shown by a curved arrow in Figure 5, and when the right hand lug 66 is free the back plate can be withdrawn along a direction lying in a radial plane (the plane of the paper, in Figure 5) as indicated by a straight arrow in the drawing Installation of the back plate 12 is done by the reverse process, first inclining the back plate 12 to its "seated" orientation to allow insertion of the lug 65 into the undercut 68 by advancing the back plate, then rotating the back plate to seat it on the torque plate.

When seated on the torque plate 4, the back plate 12 -and the friction pad 14 which it carries -is able to move along the axial direction, perpendicular to the plane of the paper in Figure 5, when moved by the actuator 36, 56.

To secure the back plate 12 in position on the torque plate 4, it is merely necessary to prevent it from rotating. This can be done using a constructionally simple retaining clip arrangement, as will now be explained.

A first retaining clip arrangement is illustrated in Figure 7 and comprises a roll pin type spring 80 The inboard back plate 12 and the torque plate 4 have in this embodiment part-circular features 82,84 (see Figure 5) which together define a recess into which sprung, cylindrical body 86 of the spring 80 is a snap fit As well as maintaining the back plate 12 in place, the spring 80 applies a biasing force to the back plate to minimise rattle and clunk, it will be apparent from Figure 7 that the force applied by the spring has both circumferential (leftward) and radially inward components The left hand lug 65 is consequently urged into the "V" formed by convergent surfaces 72, 77 and in this way circumferential and radial backlash of the lug 65 is taken up. The radial component of the spring's force urges the right hand lug 66 against its seating surface 76 to take up backlash in this region Note that during a forward braking operation the brake disc drives the back plate 12 along the same (letlward) direction as the spring 80, so that no clunk results when the brake is applied.

Figures 8 and 9 show two different versions of the roll pin type spring, either of which can be used in this context In both drawings the spring's cylindrical body is again seen at 86. In Figure 8 this is connected through a neck 92 to a locating portion 94 After pushing the body 86 into place, the spring is rotated to cause wings 96, 98 of the locating portion to clip into place around the torque plate and locate the spring against axial withdrawal. Figure 9 shows an alternative in which an elbowed arm 100 has a short return 102 to be clipped into place against the torque plate 4.

The alternative retaining clip arrangement illustrated in Figures 10 and 11 uses a captive spring which automatically clips into place when the back plate 12 is assembled with the torque plate 4. The spring 104 has a flat body 106 through which it is fastened, e g riveted, to a face of the inboard back plate 12. First and second integral spring arms 106, 108 extend from the body 106, each arm being inclined with respect to the other. Both are elbowed to provide respective spring portions whose roots 110,112 can just be seen in the drawings. Note from Figure 10 that the right hand limb 10 of the torque plate 4 is in this embodiment shaped to provide a lead-in surface or ramp 114 along which the first spring portion 110 rides as the back plate 12 is rotated into position, the inclination of the ramp being chosen to pre-stress that portion in the process, so that when it reaches a shallow recess 116 at the base of the lead-in, it snaps into the recess to secure the back plate 12 in place. The first spring portion 110 biases the back plate 12 circumferentially. The second spring portion 112 acts against an inclined surface 118 of the torque plate 2 adjacent the shallow recess I 16 and, by taking up any play in the radial direction, minimises rattle.

In the present embodiment the caliper body 34 is mounted solely through its couplings to the inboard and outboard brake pads 12, 14 and 22, 24. This, coupled with the above described manner of installation of the inboard brake pad 12, 14, makes the brake particularly straightforward to assemble and disassemble. The outboard back plate 22 is first slipped onto its guide pins 16, 17 (Figure 3). The inboard pad 12, 14 is then clipped onto the piston 56 carried by the caliper body 34 and the resulting sub-assembly, comprising the actuator, caliper body and pad, is mounted by advancing and rotating the assembly as previously described (Figure 5).

The caliper body's abutment 42 is thereby brought into position outboard of the outboard brake pad 22, 24, whose coupling 44 can then be clipped into place on the cahper body Engagement of the retaining clip 80 or 104 completes the process. The assembled brake is best seen in Figure 4.

The brake assembly of Figures 13-15 is in many respects similar to the one described above. It again has an inboard brake pad, comprising an inboard back plate 212 and friction pad 214, which is received and embraced by a torque plate 204. An outboard pad comprising outboard back plate 222 and outboard friction pad 224 is axially slidably mounted on guide pins 216, 217. The caliper body is not shown in these drawings but is formed similarly to the one seen in Figure 1 The present embodiment differs from the earlier one with regard to the shape of the torque plate 204 and of the inboard back plate 212 The mating region of the torque plate 204 which serves to receive and make captive one end of the back plate 212 is to the right in Figure 13. In place of the flat-bottomed "V" shape of the earlier embodiment, it has an undercut formed as a part-circular recess 268 facing along the circumferential direction. Lug 265 of the inboard back plate 212 has a complementary convex partcircular profile to engage with the recess. Note that as before a part of the surface of the recess faces generally radially inwardly and so traps a shoulder formed by the outer surface of the lug, making the lug captive while the remote, left hand, end of the back plate 212 is seated upon the torque plate 204 The profiles of the lug and recess assist in avoiding brake squeal This is a well-known phenomenon in which the brake pad is subject to an undesirable turning moment (tending to cause it to rotate about an axis perpendicular to the plane of the paper in Figure 13)through its abutment with the torque plate. if the pad turns very slightly in its mountings under the influence of this moment, its region of abutment with the torque plate may then move, altering the moment applied to the pad In the worst cases, this results in oscillatory behaviour and noise. in the present embodiment the external radius of the profile of the lug 265 is slightly smaller than the internal radius of the recess 268, so that the abutment between the two is limited to a narrow line. Hence the contact between the two is well defined and changes little, avoiding oscillatory behaviour In the present embodiment there is no clip to couple piston 256 to the inboard hack plate 212. Instead the back plate and the piston have complementary locating features which interlock. Specifically the back plate 212 carries locating projections 300 which are received in the mouth of the piston. The projections lie on a circular locus, whose diameter may be chosen to make them a press fit in the piston. The illustrated embodiment has three such projections. Note that once the brake has been assembled and the inboard pad locked in place, the piston is captive since it cannot be axially withdrawn far enough to disengage from the projections 300 The projections 300 may be formed as semi-shears This is a well-known technique in which a press tool applied to one face of the workpiece serves, without passing all of the way through it, to raise a projection on the other side. The profile of the back plate 212 and its projections 300 may be formed from sheet material in a single operation, which is economical.

in Figure 15 it can be seen that the clip 244 used to couple the outboard back plate 222 to the caliper body is secured to the back plate through two stubs 302.

These too are formed as semi-shears and are received in openings in the clip 244, after which the stubs 302 are swaged to keep the clip in place. Figure 16 shows a modified version of the inboard back plate 212, which in this case has two through-going holes 3 10, 3 12 which receive complementarily positioned stubs formed on the caliper body, which is thereby located against rotational movement.

The aforegoing embodiments are presented by way of example only Numerous variations are possible without departing from the scope of the present invention

Claims

CLAIMS

I A brake pad arrangement for a disc brake, the arrangement comprising a carrier, a first brake pad, and a second brake pad, the carrier being adapted to be fixedly mounted on one side of a brake disc defining an axis, and being shaped to provide a cradle which is radially open, enabling the first brake pad to be introduced to the cradle by moving it along a radial plane and thereby to be axially movably mounted, the cradle providing opposed abutment surfaces by which the first brake pad is circumferentially located, the arrangement fbrther comprising a pair of axial mounting projections fixedly coupled to the carrier, the second brake disc being shaped to receive and embrace the mounting projections and thereby to be axially movably mounted on the other side of the brake disc, the pins serving to locate the second brake pad both circumferentially and radially 2 A brake pad arrangement as claimed in claim 1, in which the second brake pad has through-going bores which receive the respective mounting projections.

3 A brake pad arrangement as claimed in claim I or claim 2, in which the carrier is formed as a shaped plate and the mounting projections are formed as pins mounted in the plate 4 A brake pad arrangement as claimed in any preceding claim, in which the cradle is formed by a pair of radially outwardly extending limbs between which the first brake pad is received A brake pad arrangement as claimed in any preceding claim, in which the carrier has an undercut and the first brake pad assembly has a shoulder formed to engage with the undercut and thereby to be radially located.

6 A brake pad arrangement as claimed in claim 5, in which the formation of the first brake pad and the carrier part is such that to engage them requires the first brake pad to be advanced to introduce the shoulder to the undercut, and then to be rotated to seat it upon the carrier 7 A brake pad arrangement as claimed in claim 6, thrther comprising a retainer for rotationally locating the first brake pad and so retaining it upon the carrier, the retainer being releasable by a user 8 A disc brake comprising a brake pad arrangement as claimed in any preceding claim and a caliper body which carries an actuator for applying a force to one of the brake pads and which engages with the other of the brake pads to react the force to it, wherein the caliper body is axially movably mounted by engagement with the brake pads 9. A disc brake as claimed in claim 8, in which the caliper body engages with at least one of the brake pads through inter-fitting male and female engagement features introducible to each other along the axial direction, and in which disengaging these parts requires de-mounting of at least one of the brake pads A disc brake as claimed in claim 8 or claim 9, in which the male engagement feature(s) are formed as semi-shears in a back plate of the brake pad 11 A disc brake as claimed in claim 10, in which the female engagement feature is an open mouth of a piston part of the actuator.

12 A torque plate for a disc brake which is adapted to be fixedly mounted alongside a brake disc having an axis and which is shaped to define a cradle for receiving a first brake pad, the cradle providing opposed abutment surfaces for circumferentially locating the first brake pad and being radially open to enable it to receive the first brake pad along a radial direction, the torque plate having two openings for receiving and mounting axially projecting pins for mounting a second brake pad 13 A torque plate as claimed in claim 12, in which the cradle is defined by a circumferentially spaced pair of arms whose opposed surfaces provide the abutment surfaces 14 A torque plate as claimed in claim 12 or claim 13, in which a first one of the arms has an undercut for receiving a complementarily formed shoulder of the first brake pad and for trapping the shoulder to prevent its withdrawal along a radial direction.

1 5 A torque plate as claimed in claim 14, in which a second one of the arms is shaped to receive a retainer for rotationally locating the first brake pad 16 A torque plate as claimed in claim 15, in which the second arm comprises a ramp surface leading to a recess for receiving a retainer formed as a spring clip.

I 7 A torque plate as claimed in claim 15, in which the second arm comprises a part-circular recess for receiving a spring pin 18 A back plate for a brake pad, formed as a shaped metal plate having a first face for carrying a pad of friction material and a second face opposite the first for engaging with a device for applying a braking force, the second face having projections for locating the brake pad relative to the aforesaid device and the projections being formed as semi-shears. - 19 A back plate as claimed in claim 18 ftirther comprising a pair of through-going openings for receiving pins to mount the back plate A back plate as claimed in claim 18 at opposite extremities of which are integral lugs for engaging with a torque plate.

21 A back plate as claimed in claim 20 in which at least one of the lugs has a part-circular profile 22 A back plate as claimed in claim 20 in which at least one of the lugs has a "V" shaped nose.

23 A back plate as claimed in any of claims 18 to 22, which is a pressed metal component.

24 An assembly for use in a disc brake, comprising a carrier adapted to be fixedly mounted adjacent a brake disc and a brake pad adapted to seat upon the carrier and so to be mounted by it such as to be movable along an axial direction, the carrier having opposed surfaces which, by abutment with the brake pad, serve to circumferentially locate it, wherein the carrier has an undercut and the brake pad has a complementarily formed shoulder, the formation of the carrier and the brake pad enabling the pad to be installed by inclining the pad to its mounted orientation and advancing the pad along a direction in a radial plane to introduce the shoulder to the undercut, then rotating the brake pad to seat it upon the carrier, causing the shoulder to be trapped by the undercut so that the brake pad cannot subsequently be withdrawn along the radial plane without rotating it.

An assembly as claimed in claim 24, in which the carrier comprises a pair of radially outwardly extending limbs between which the brake pad is received.

26 An assembly as claimed in claim 25, in which the undercut is formed on one of the limbs, the other limb having a seating surface to which the brake pad is introducible by the aforesaid rotation 27 An assembly as claimed in any of claims 24 to 26, which further comprises a retainer for rotationally locating the brake pad and so retaining it upon the carrier, the retainer being releasable by a user 28 An assembly as claimed in claim 27, in which the retainer comprises a spring clip.

29 An assembly as claimed in claim 28, in which the spring clip is mountable on one of the brake pad and the carrier such as to engage automatically when the brake pad is seated upon the carrier.

An assembly as claimed in claim 29, in which one of the brake pad and the carrier carries the spring clip and the other is shaped to provide a ramp surface along which the spring clip rides as the brake pad is rotated to seat it upon the carrier, the inclination of the ramp surface being such that the spring clip is thereby stressed, and the ramp surface leading to a recess, so that when the brake pad arrangement reaches its seated position the spring clip engages in the recess.

31 An assembly as claimed in any of claims 28 to 30, in which the spring clip serves to apply a biasing force to the brake pad and so to take up backlash between the brake pad and the carrier.

32 An assembly as claimed in claim 3 1 in which the spring clip circumferentially biases the brake pad toward convergent mating surfaces of the carrier, thereby taking up both circumferential and radial backlash in this region.

33 An assembly as claimed in any of claims 28 to 32, in which the spring clip serves to radially bias the brake pad and so to take up backlash between the brake pad and the carrier 34 An assembly as claimed in claim 33 in which the spring clip comprises two sprung tongues which are inclined to each other and respectively serve to bias the brake pad radially and circumferentially An assembly as claimed in any of claims 24 to 34, in which the spring clip comprises a resilient pin receivable by aligned, complementarily shaped recesses of the brake pad and the carrier.

36 An assembly as claimed in any of claims 24 to 35, which further comprises a caliper body and an arrangement for coupling the caliper body to the brake pad.

37 An assembly as claimed in claim 36, in which one of the brake pad and the caliper body carries a coupling clip, the other being shaped to receive the coupling clip to couple the caliper body to the brake pad.

38 An assembly as claimed claim 36 or claim 37, in which the coupling of the brake pad to the caliper body is through an actuator carried by the caliper body, the brake pad being coupled to a movable part of the actuator.

39 An assembly as claimed in claim 37 or claim 38, fl.zrther comprising a second brake pad which is axially movably mounted.

An assembly as claimed in claim 39, in which the carrier has at least one axially extending guide, the second brake pad slidably engaging with the guide and so being circuniferentially located.

41 An assembly as claimed in claim 40, comprIsing a pair of axially extending guides formed as pins projecting from the carrier and received by openings in the second brake pad.

42 An assembly as claimed in any of claims 39 to 41, in which one of the second brake pad and the caliper body carries a second coupling clip, the other being shaped to receive the second coupling clip to couple the caliper body to the second brake pad.

43 A brake pad for use in an assembly as claimed in any of claims 24 to 42, comprising a friction pad secured to a back plate, the back plate being shaped to provide the aforementioned shoulder 44. A brake pad as claimed in claim 43, further comprising a coupling clip secured to the back plate for coupling the back plate to a caliper body.

A brake comprising an assembly as claimed in any of claims 39 to 41 in which the caliper body is axially movably mounted solely by virtue of its being coupled to one or both brake pads 46. A brake as claimed in claim 45 which further comprises means for releasably coupling the caliper body to the inboard brake pad assembly through the actuator to form an assembly comprising the actuator, caliper body and inboard pad which is able to be installed/removed by engaging/disengaging the inboard pad with/from the carrier 47 A brake as claimed in claim 45 or 46, in which the inboard pad and the carrier are formed such that the inboard pad is able to be introduced to the carrier by moving it along a direction lying in a radial plane, thereby engaging complementary mating surfaces of the inboard pad and the carrier to circumferentially locate the inboard pad.

48 A brake as claimed in claim 47, further comprising an arrangement for releasably radially locating the inboard pad to maintain it in position.

49 A brake as claimed in claim 47 or claim 48, in which the carrier has an undercut and the inboard brake pad has a shoulder formed to engage with the undercut and thereby to be radially located.

A brake as claimed in claim 49, in which the formation of the inboard pad and the carrier part is such that to engage them requires the inboard pad to be advanced to introduce the shoulder to the undercut, and then to be rotated to seat the inboard pad upon the carrier 51 A brake as claimed in any of claims 45 to 50, in which the carrier is provided with at least one axially extending guide and the outboard brake pad slidably engages with the guide and so is circumferentially located but axially movable.

52 A brake as claimed in any of claims 45 to 51, in which the outboard brake pad is mounted solely by virtue of its being coupled to the caliper body.

53 A brake substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

54 A brake pad arrangement substantially as herein described with reference to, and as illustrated in, the accompanying drawings A torque plate for a disc brake, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.