GB2108224A - Improvements in or relating to disc brakes - Google Patents

Abstract

A disc brake comprises a disc (11) carried by a hub (10) to be rotationally fast therewith but axially movable relative thereto, the disc having at its circumference an annular groove (12), a fixed bracket (13) projecting into the groove, and actuating means (17) which is located in the groove and is operable to apply braking shoes (14A, 14B) axially against the flanks (15A, 15B) of the groove (12); actuating means (17) comprise an actuating element (18) circumferentially movable in groove (12) and co-operable with cam means (19) adapted to generate an axial separating force in response to a circumferential movement of said actuating element (18). The shoes (14A, 14B), bracket (13), actuating element (18) may be annular or formed of two diametrically opposite parts. The disc (11) may be of two-part construction (11A, 11B) - and subjected to elastic means (28). The cam means (19) comprise at least two ramps which may extend transversely obliquely or as shown in Figure 5 - and various arrangement of the actuating means and its cam means are disclosed. <IMAGE>

Description

SPECIFICATION Improvements in or relating to disc brakes The present invention relates generally to disc brakes.

As is known, a disc brake comprises, in combination a braked rotary hub, a braking disc, two braking shoes, and actuating means adapted to act axially to apply said braking shoes against said disc.

The present invention deals more particularly with the case where the disc is of the grooved type, or of U-shaped cross-section, such a disc having at its circumference an annular radial, groove into which the fixed bracket projects radially, and in which both the braking shoes and the actuating means are arranged.

It is an object of the present invention to provide an arrangement which enables the axial dimension of such a brake to be minimised, and hence facilitates positioning of the brake, particularly on certain heavy vehicles within which the available space is only small.

According to the invention there is provided a brake of the type comprising a braked rotary hub, a braking disc which is fixed in rotation on said hub and which exhibits a radial groove annularly on its circumference, a fixed bracket which penetrates radially into said groove, two braking shoes which are arranged each respectively facing the flanks of the said groove in the latter, and actuating means which, arranged in said groove, are adapted to act axially to apply said braking shoes against the flanks of said groove, this brake being characterised in that, in combination, the disc is fitted axially movably on the hub which carries it, and the actuating means comprise an actuating piece fitted circumferentially movable in the groove of said disc, in cooperation with cam means adapted to generate an axial separating force in response to a circumferential movement of said actuating piece.

The axial space occupied by the actuating means within the groove of the disc is reduced by virtue of such an arrangement, and the same applies to that of the fixed bracket and, consequently, the axial dimension of the whole is itself advantageously reduced.

In practice, in the groove of the disc, the fixed bracket according to the invention forms on the one hand a cheek perpendicular to the axis of the hub, and on the other hand a crown parallel to said axis, and the actuating piece, which extends parallel to said cheek, is axially in abutment against the same, optionally through the intermediary of a distance element, and is centred on said crown, optionally through the intermediary of a bushing.

Likewise in practice, one of the braking shoes is formed by the fixed bracket, said fixed bracket carrying a friction lining for this purpose, whilst the other braking shoe, which is axially movable as customary, is engaged on the crown of said fixed bracket, being fixed in rotation thereon, for example by a channelled fitting.

Thus, according to the invention, the fixed bracket in itself assumes a plurality of functions in a simple manner: it absorbs the braking torque, it provides an axial abutment for the actuating piece, and it effects the centering of the latter.

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which Figure lisa partial view in axial section of the brake according to the invention, along the broken line I-I of Figure 2; Figure2 is a partial view of the same in elevation, viewed in the direction of arrow II of Figure 1; Figure 3 is a partial view of the same in crosssection, along the line Ill-Ill of Figure 1; Figure 4 is a partial view of the same in plan, viewed in the direction of arrow IV of Figure 1 in which the various members of the brake according to the invention have been mutually separated axially; and Figure 5 is a view partly repeating that of Figure 4 on a larger scale, and assumed developed flat, for a preferred embodiment.

As illustrated in the drawings, and as known per se, the brake according to the invention comprises a braked rotary hub 10, a braking disc 11 which is rotationally fast on said hub 10, and which has at its circumference an annular, radial groove 12, a fixed bracket 13 which projects radially into said groove 12 of the disc 11, two braking shoes 14A, 14B which are arranged each respectively facing the flanks 15A, 15B of said groove 12, in the latter, and actuating means 17 which, detailed below, are likewise arranged in said groove 12 and are adapted to act axially to apply the braking shoes 14A, 14B against the flanks 15A, 15B of said groove 12 of the disc 11.

The disc 11 is fitted so as to be axially movable on the hub 10 which carries it, and, as detailed below, the actuating means 17 comprise an actuating element 18 fitted circumferentially movable in the groove 13 of said disc 11, in cooperation with cam means 19 adapted to generate an axial separating force in response to a circumferential movement of said actuating element 18.

In the embodiment illustrated, a channelled interconnection 20 is provided between the disc 11 and the hub 10, on a bearing surface on a portion 21 of the hub of enlarged diameter. On the opposite side to the fixed bracket 13, said disc 11 comprises a stop collar 23 for axial abutment against a shoulder 24 of the hub 10 formed by the corresponding end cross-section of said enlarged diameter portion 21, whilst on the side of the disc adjacent the fixed bracket, the disc 11 is subjected to elastic means which permanently urge it axially towards said shoulder 24 of the hub 10.

In practice, in the embodiment illustrated, the disc 11 is of two parts suitably mutually assembled by screws 26, namely a first part 1 1A, of L-shaped cross-section, on which the channels of the channelled interconnection 20 are formed, and a second part 11 B, of straight cross-section, on which the stop collar 23 is formed.

In the embodiment illustrated, the elastic means associated with the disc 11 comprise a plurality of elastic strips 28 which extend radially and which are attached to the disc 11 by screws 30 at one of their ends, whilst their other end bears against the hub 10, and more specifically against the end transverse face of the portion of enlarged diameter 21 opposite that upon which the shoulder 24 is formed.

In practice, a plurality of elastic strips 28 distributed circularly are provided and with each of them there is associated a rigid plate 32 which, attached to the disc 11, for example, and as shown, by the corresponding screw 30, is adapted to counter-abut such an elastic strip 28 in order to limit its deformation.

As a variant, the elastic strips 28 may all belong to one and the same annular washer, and likewise, the plates 32 may all belong to one and the same annular abutment means associated with said washer.

Lastly, in the embodiment illustrated, the disc 11 carried externally fins 33 for ventilation.

Outside the groove 12 of the disc 11, the fixed bracket 13 comprises, parallel to the axis of the whole, a wall 35 by which it is adapted to be attached to any bracket 36 by means of screw 38 passing through axial passages 39 in the wall 35, and, in the embodiment illustrated, the wall is recessed with an indentation 40.

In the groove 12 of the disc 11, the fixed bracket 13 has a wall 42 perpendicular to the axis of the hub 10, adjacent the flank 15A of said groove 12, and a crown 43 parallel to said axis.

According to one aspect of the invention, the braking shoe 14A is formed by the fixed bracket 13, the wall 42 of the latter carrying for this purpose, a friction lining 45A, the flank 15A of the groove 12 of the disc 11. The friction lining 45A may be secured, for example, by gluing. The braking shoe 14B is fitted so as to be axially movable, as customary.

The braking shoe 14B is adapted to be axially movable with reference to the fixed bracket 13, whilst being rotationally fast on the latter.

In practice, in the embodiment illustrated, the braking shoe 14B, which is formed as customary by a bracket plate 44B and by a friction lining 45B suitably attached to the latter, for example by gluing, is engaged by said bracket plate 44B upon the crown 43 of the fixed bracket 13, being rotationally fast on the latter.

For example, and as illustrated, a chanelled interconnection 47 is provided for this purpose between the bracket plate 44B of the braking shoe 14B and the end of the crown 43 of the bracket 13, on the outer surface of the latter.

In practice, both the fixed bracket 13 and the braking shoes 14A, 14B are annular members in the embodiment illustrated.

The same applies to the actuating element 18. The latter, which extends parallel to the wall 42 of the fixed bracket 13, is axially in abutment against the wall 42.

In the embodiment illustrated, this abutment occurs through the intermediary of a spacing element 49, and the latter is divided circularly into spacing elements carried axially projecting by the fixed bracket 13 on its wall 42.

Thus the position of the actuating element 18 is well defined axially with reference to the fixed bracket 13, and hence with reference to the main bracket 36.

A washer 51, bearing against a, for example, split ring 52 engaged in an annular groove of the crown 43 of the fixed bracket 13, axially counter-abuts the actuating element 18 on the side of the element 18 opposite the split ring 52.

According to the invention, the actuating element 18 is centered on the crown 43 of the fixed bracket 13, and in the embodiment illustrated, this centering occurs through the intermediary of a bushing 54.

Lastly, at its external circumference, the actuating element 18 has radially projecting a protuberance 55 for action, in the direction of arrow F of Figure 2, by any actuating member not shown, for example a jack, adapted to act substantially tangentially to the circumference of the whole.

Generally speaking, the cam means 19 associated with the actuating element 18 comprise at least two ramps 56, 56', of which one, the ramp 56 is fixed to said actuating element 18, and of which the other, ramp 56' is fixed to the braking shoe 14B.

In the embodiment illustrated in Figures 1 to 4, each ramp 56 belongs to a protuberance 57 axially projecting from the actuating element 18, and the ramp 56' belongs similarly to a protuberance 57' axially projecting from the bracket plate 44b of the braking shoe 14B.

The protuberances 57,57' are directed axially towards each other, and the ramps 56, 56' which they carry are mutually complementary.

In practice, these ramps 56, 56' extend transversely obliquely with reference to the axis of the whole, and a plurality of protuberances 57, 57', distributed circularly, are provided annularly on the actuating element 18 and on the bracket 44B of the braking shoe 14B, in the manner of complementary tooth systems.

The actuating element 18 and the braking shoes 14A, 14B are mutually imbricated by these protuberances 57, 57'.

At rest, Figure 1, the stop collar 23 of the disc 11 is urged by the pressure of the elastic strips 28 into abutment against the transverse shoulder 24 of the hub 10, and a slight play exists axially between the flank 15A of the groove 12 of said disc 11 and the braking shoe 14A on the fixed bracket 13.

Likewise, a slight play exists axially between the braking shoe 14B and the flank 15B of the groove 12 of the disc 11.

During braking, and under the stress of the actuating member, which acts on it, the actuating element 18 undergoes a circumferential displacement in the direction of the arrow F in Figure 2, which displacement is of limited amplitude in practice.

Bearing against the fixed bracket 13, and more specifically against the wall 42 of the latter, the actuating element 18 then causes, by means of the ramps 56 of its protuberances 57, an axial displacement, in the direction of the arrow F' in Figure 1, of the braking shoe 14B towards the flank 15B of the groove 12 of the disc 11, until the braking show 14B is applied against the flank 15B.

This movement being continued, the disc 11 itself undergoes an axial movement in the direction of the arrow F' of Figure 1, which occurs counter to the elastic strips 28, and which causes the flank 15A of its groove 12 to the applied against the braking shoe 14A on the fixed bracket 13.

The disc 11 is then braked due to the mutual axial separation of the braking shoes 14A, 14B caused by the cam means 19.

When the action exerted upon the actuating element 18 is relaxed, the latter returns to its initial position, for example, by return means not shown, for example a simple spring, and the disc 11 likewise returns to its initial position.

In the preferred embodiment illustrated in Figure 5, each of the ramps 56 on the actuating element 18 belongs to a groove 60, whilst, as previously, each of the ramps 56' correspondingly on the bracket plate 44B ofthe braking shoe 14B belongs to a protuberance 57'.

In practice, such a groove 60 extends between a steep face 61, axial for example, as shown, which corresponds to the intial rest position of the actuating element 18, and a less inclined face formed by the corresponding ramp 56.

The floor 62 of this groove preferably has circumferentially a rounded profile, and for example, as illustrated, a circular profile of radius R.

Likewise preferably and as illustrated, the ramp 56 has a point of inflexion 64, for example of 45 , and, contrary to the steep face 61 of the groove 60, it ends in a less inclined rectilinear portion 65, for example of 25 , tangentially to its current part.

The ramp 56 is of course tangentially in continuity with the floor 62 of the groove 60 to which it belongs, and its point of inflexion 64 may for example mark its connection to the circular profile of this floor 62.

If desired, the point of inflexion 64 may be replaced by a straight portion.

In any event, in the illustrated embodiment, the grooves 60 of the actuating element 18 are mutually circumferentially spaced by intermediate flats 66.

The same applies to the protuberance 57' of the bracket plate 44B of the braking shoe 14B.

In the illustrated embodiment, each of these protuberances 57' has circumferentially a rounded profile, at least at its end, such a profile possibly being preceded, as illustrated, by a straight portion parallel to the axis of the whole.

In practice, the profile of each of the protuberances 57' is circular and its radius R' is slightly less than the radius R of the profile of the floor 62 of the associated grooves 60.

As will easily be understood, the steep face 61 of the grooves 60, in cooperation with the corresponding flank of the protuberances 57', ensures as well-defined initial rest position of the actuating element 18.

In use, the part of the ramps 56 which is upstream of their point of inflexion 64, and which therefore has an increasing inclination, advantageously ensures a rapid approach of the braking shoes 14A, 14B with respect to the corresponding flanks 15A, 15B of the groove 12 of the disc 11, up to contact with the latter.

The part of these ramps 56 which is downstream of their points of inflexion 64, and which therefore exhibits a decreasing inclination, then advantageously ensures the required clamping in a more progressive manner.

So that the contact between them occurs along a straight line, and not at a simple point, furthermore not controllably positioned, the ramps 56, 56' are preferably adjusted surfaces, the generatrices of which intersect the axis of the whole, so that with reference to said axis, their external and internal circumferences are both totally contained in one and the same angular sector.

Thus a particularly advantageous compromise is found between, on the one hand, obtaining an extended zone of contact between said ramps 56, 56', which is favourable to minimising the pressure of their contact, and therefore the wear and/or risks of jamming, and, on the other hand, an acceptable facility of production for these ramps 56, 56'.

The present invention is of course not limited to the embodiments described and illustrated, but embraces all modifications within the scope of the appended claims.

Particularly, it is not essential for the fixed bracket and/or the braking shoes and/or the actuating element to consist of annular members.

Such members, or at least some of them, might on the contrary equally well be, for example, each formed of two parts arranged in diametrically opposite positions with respect to each other.

In such a case, the disc is not necessarily of two parts either, such a two-part construction of the said disc obviously being essential only in case any integral annular member has to be fitted into the groove of the same.

Furthermore, the spacing element 49 or the spacing elements forming the latter, is not necessarily an integral part of the fixed bracket 13; it could equally well be an integral part of the actuating element 18.

As a variant, it comprises a member independent of both the fixed bracket 13 and the actuating element 18.

In this case, it is preferably made of an antifriction material to minimise the friction between the actuating element 18 and the fixed bracket 13 and thus to facilitate the circumferential movement of said actuating element 18.

In all cases, the respective roles of the ramps forming the cam means may evidently be interchanged from the actuating element to the corresponding braking shoe.

In practice, dealing with the embodiment illustrated in Figure 5, the groove 60 may belong to the respective braking shoe 14B,-in which case the corresponding protuberances 57' belong to the actuating element 18.

Claims (19)

1. A brake comprising a braked rotary hub, a braking disc carried by the hub to be rotationally fast therewith and axially movable relative thereto, the braking disc having a radial groove extending annularly around its circumference, a fixed bracket radially projecting into said groove, two braking shoes each arranged respectively facing the internal flanks of the groove in the disc, and actuating means which are disposed in the groove and which are operable to apply axially the braking shoes against the flanks of the groove, means comprising an actuating element circumferentially movably mounted in the groove of the disc and being cooperable with cam means adapted to generate an axial separating force in response to a circumferential movement of the actuating element.

2. A brake according to claim 1, wherein one of the braking shoes is formed by the fixed bracket, said fixed bracket carrying a friction lining, whilst the other braking shoe is axially movable.

3. A brake according to claim 2, wherein the cam means comprise at least two ramps, one of which is fixed to the actuating element and the other of which is fixed to the movable braking shoe.

4. A brake according to claim 3, wherein said ramps are complementary and extend transversely obliquely with reference to the axis of the hub.

5. A brake according to claim 3, wherein one of said ramps belongs to a groove, and the other to a protuberance.

6. A brake according to claim 5, wherein the groove to which one of said ramps belongs extends between a steep face, which corresponds to the initial rest position of the actuating element, and a less inclined face, which forms said ramp.

7. A brake according to either of claims 5 and 6, wherein the ramp which belongs to a groove has a point of inflexion.

8. A brake according to either of claims 6 and 7, wherein the ramp which belongs to a groove terminates in a straight portion contrary to the steep face of said groove.

9. A brake according to any of claims Sto 8, wherein the protuberance to which one of the ramps belongs has a rounded profile circumferentially.

10. A brake according to claim 9, wherein said protuberance has a circular profile circumferentially, as has the floor of the associated groove, and the radius of the profile of said protuberance is slightly less than that of the profile of said floor.

11. A brake according to any of claims 3 to 10, wherein said ramps belong to adjusted surfaces, the generatrices of which intersect the axis of the whole.

12. A brake according to any of claims 1 to 11, wherein the actuating element is annular.

13. A brake according to any of claims 1 to 12, wherein, in the groove of the disc, the fixed bracket comprises a wall perpendicular to the axis of the hub and a crown parallel to said axis.

14. A brake according to claims 12 and 13, wherein the actuating element is centered on the crown of the fixed bracket, optionally th rough the intermediary of a bushing.

15. A brake according to claims 12 and 13, wherein the wall of the fixed bracket carries the associated friction lining, and the rotation thereon, by a channelled fitting.

16. A brake according to claim 13, wherein the actuating element extends parallel to the wall of the fixed bracket and is axially in abutment thereagainst, optionally through the intermediary of a spacing element.

17. A brake according to any of claims 1 to 16, wherein on the opposite side to the fixed bracket, the disc comprises a stop collar for axial abutment against a shoulder of the hub, and on the side of the fixed bracket it is biassed by elastic means which urge it axially towards said shoulder of the hub.

18. A brake according to any of claims 1 to 17, wherein the actuating element has a radially projecting protuberance on which can act an actuating member, such as a jack.

19. A brake substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4, or Figure 5 of the accompanying drawings.