GB2054075A

GB2054075A - Adjustment mechanism for automatic compensation of brake lining wear of a disc brake

Info

Publication number: GB2054075A
Application number: GB8020219A
Authority: GB
Original assignee: Deutsche Perrot Bremse GmbH
Current assignee: Deutsche Perrot Bremse GmbH
Priority date: 1979-06-22
Filing date: 1980-06-20
Publication date: 1981-02-11
Also published as: IT1132106B; DE2925342A1; GB2054075B; ATA283980A; AT384866B; IT8022751A0; FR2459910B1; FR2459910A1

Abstract

The brake has a brake activation mechanism (7) comprising a screw (15) and a nut (12), which on its exterior has a helical gear(13); an adjustment shaft (24) is mounted in a bore transverse to the direction of its displacement of the nut (12) and has a helical gear which engages the helical gear (13) of the nut, and the adjustment shaft (24) is axially displaceable in a clearance range "L" which corresponds to the release clearance of the brake; on wear of the lining the adjustment shaft (24) is adapted to be rotated during brake activation by an amount corresponding to the degree of wear while overriding a frictional anti- rotation lock (30, 33); during brake release nut (12) is rotated and screw 15 is screwed out. The lock is formed by interengagement of shoulder (33) of a sleeve (28) rotationally fast with shaft (24) and a conical bore (30) of a screw (29). Release clearance "L" is adjustable using a grub screw 37. <IMAGE>

Description

SPECIFICATION Adjustment mechanism for automatic compensation of brake lining wear of a disc brake This invention relates to an adjustment mechanism for the automatic compensation of brake lining wear of a disc brake having a brake saddle which is mounted on the brake carrier for displacement transversely to the brake disc and embraces with its two shanks the brake disc as well as the two brake lining carriers provided with brake linings arranged on either side of the brake disc, and a brake activation mechanism for engaging brake lining carrier in the direction of the brake disc against the action of a return spring.

In known mechanically operated disc brakes usually use is made of an activation mechanism which converts a pivoting movement into an axial movement. In these there is associated with the pivoting axis of the activation lever an axially displaceable pressure piece, which cooperates with the activation lever either directly via surfaces inclined to the radial plane or indirectly via suitably constructed ball bearings. The brake lining carriers are at the same time either located either side of the brake disc within the brake saddle which embraces the brake disc. They can also be located on brake levers which cooperate like calipers, whose free ends are pressed apart on activation of the brake.With disc brakes of the last-mentioned type (DE-OS 1425237) in which the activation mechanism lies between the two outer caliper lever ends, there are particular difficulties in installing the adjustment mechanism, particularly as the construction of the activation mechanism is relatively complex. In a further development of this (DE-OS 2729641) it is true that easier mounting of the expander mechanism is ensured. However, automatic adjustment does not take place here either.

The invention has as its task to create an adjustment mechanism for automatic compensation of brake lining wear of a disc brake having a brake saddle oF the above-mentioned type.

The adjustment mechanism according to the invention, in which this task is solved, is characterised substantially in that, engagement of the brake lining carrier is achieved by means of a screw and a nut, which on its exterior has a helical gear, that an adjustment shaft which is mounted in a bore transverse to the direction of displacement of the nut has a helical gear which engages the helical gearing of the nut and that the adjustment shaft is axially displaceable in a clearance range "L", which corresponds to the release clearance of the brake on its activation and that on wear of the lining the adjustment shaft can be temporarily rotated by an amount corresponding to the degree of wear while overriding a frictional anti-rotation lock.

To provide a frictional anti-rotation lock it has been proved constructionally very advantageous if the adjustment shaft is made rotationally fast to a sleeve which is acted on by a spring, which sleeve abuts a conical bore which has a predetermined position relative to the brake saddle with an edge provided on a radially projecting shoulder of the sleeve. For this it is advantageous if the clearance "L" can be adjusted by adjustment of the position of the conical bore relative to the brake saddle. For this purpose advantageously a screw is provided formed with such a conical bore, rotation of which allows the clearance "L" to be adjusted.

In a further advantageous embodiment the sleeve is made rotationally fast to the adjustment shaft by means of a pin whose ends engage in longitudinal slits in the sleeve and which passes through the adjusting shaft.

A specific embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, wherein: Figure 1 is a side view of a brake-carrier-brake- saddle-unit with mechanical brake activation, Figure 2 is a section through the brake-carrierbrake-saddle-unit of Figure 1 on line Il-Il, Figure 3 is a side view of a brake-carrier-brakesaddie-unit similar to that of Figure 1, however seen from the opposite end, and Figure 4 is a section through the unit according to Figure 2 corresponding to line IV-IV of Figure 2.

As can be seen from the drawing, the illustrated disc brake comprises a brake saddle 1, which is mounted on a brake carrier 2 displaceable transversely to a brake disc 3, which is merely indicated in the outline of its exterior contours.

The brake saddle 1 has two shanks 4, 4' with which it embraces the brake disc 3 as well as the two brake lining carriers 5, 5i on each side of the brake disc which respectively carry brake linings 6, 6'. The shank 4' of the brake saddle has allocated to it a brake activation mechanism referred to generally by the reference 7. This comprises a shaft 8 with an activation lever 9. As can be seen from Figure 2, the shaft 8 is provided with a recess, in which an evolute shape cam 10 is formed. This abuts against the face of a pressure piece 11. On pivoting of lever 9 the corresponding rotation of shaft 8 leads via cam 10 to displacement of pressure piece 11 in the direction of the brake disc 3. For this purpose the pressure piece 11 is guided in a bore of shank 4' of brake saddle 1.This pressure piece 11 abuts against a nut 12 which like the pressure piece 11 is mounted in a bore displaceable in the direction of the brake disc 3. This nut 12 is connected via an exterior helical gearing 13 with a now further illustrated adjustment mechanism, which is further illustrated in Figure 4 and explained in detail in the following. With an internal screw thread 14 the nut 1 2 receives a screw 1 5 which is axially moveable which is held in abutment on brake lining carrier 5' at its front end 16, and this in a similar manner as the way in which the abutment between brake lining carrier 5 on shank 4 of brake saddle 1 is ensured.As can be seen from Figure 3, for this purpose the brake lining carrier 5 is provided with a pin 1 7 on its rear with a head 1 8.

A W-shaped spring 1 9 fits around head 1 8 with its two middle shanks and with the end of its outer shanks extends into a recess of shank 4 of brake saddle 1 intended for its reception. In a similar manner there is also a connection between brake lining carrier 5' with screw 1 5. Approximately at the outer end of the bore of shank 4' of brake saddle 1 which is intended for the reception and guidance of nut 12 there is a snap-ring 20 for supporting a ring disc 21, against which one end of a helical spring 22 abuts whose other end is supported on nut 12.

On activation of the brake by rotation of shaft 8 the brake lining carrier 5' with brake lining 6' is moved towards the brake disc by means of the pressure piece 11, the nut 12 and the screw 1 5.

Due to the reaction force arising on engagement of the brake disc, the brake saddle 1 is so disposed that also brake lining carrier 5 with brake lining 6 comes into contact with the brake disc 3. During activation of the brake the helical spring 22 is compressed; on release of the brake the helical spring 22 returns the nut 12 with the screw 1 5 as well as the pressure piece 11 back to the initial position. In order that in this reieased position of the brake, that is during travel, there is a substantially equal release clearance on both sides of the brake disc 3 independently of the degree of wear of the brake linings 6, 6' there is inserted between brake carrier 2 and brake saddle 1 a device which is not further illustrated.

The adjustment mechanism illustrated in Figure 4 comprises an adjustment shaft 24, which is rotatable in a bore 25 of the brake saddle 1 which extends transversely to the direction of displacement of pressure piece 11 and which is displaceable against the action of a compression spring 26. This adjustment shaft 24 has a helical gearing 13 corresponding to the helical gearing 27 of the nut 12, through which it is in engagement with that of the nut 12. On the lower end of the adjustment shaft 24 there is seated a sleeve 28, which surrounds a screw 29, having therein conical bore 30, screwed into the expanded end of bore 25. A snap-ring 31 mounted on sleeve 28 serves for supporting one end of the compression spring 26, whose other end bears on brake saddle 1 via the screw 29.In this way the compression spring 26 acts on the sleeve 28 in such a manner that it abuts the conical bore 30 of the screw 29 with an edge 32 of sleeve shoulder 33. A pin 34 which passes transversely through the adjustment shaft 24 extends with its ends into longitudinal slits 35 of the sleeves 28. It thus provides a rotationally fast coupling between the adjustment shaft and the sleeve 28, while however allowing axial displacement of the adjustment shaft 24 relative to the sleeve 28 corresponding to the clearance "L" between the conical end of shaft 24 and the bottom of bore 25.

During such displacement the adjustment shaft 24 with its shoulder 36 disengages from sleeve 28.

The described adjustment mechanism works as follows: If during activation of the brake the nut 12 is displaced axially together with the screw 15, then this displacement leads via the engaging helical gears 13 and 27 to an axial displacement of the adjustment shaft 24. As the clearance "L" corresponds to the release clearance of the brake, which arises from the elastic deformation of the brake saddle 1 plus the release clearance between the brake lining 6, 6' and brake disc 3, the adjustment shaft 24 comes to rest in abutment against the bottom of bore 25 when the brake is fully activated. If now after several breakings there is a larger wear of brake linings 6, 6' and the nut 12 thus moves further still, then the adjustment shaft 24 is rotated via the engaging helical gearings 1 3 and 27.The sleeve 28 is then also rotated while overriding the relatively small retaining force due to compression spring 26 between the edge 32 of the sleeve shoulder 33 and the conical bore 30.

If now after termination of the braking operation the adjustment block comprising pressure piece 11, nut 12 and screw 1 5 is returned by the helical spring 22 - shaft 8 and the activation lever 9 have already moved ahead on application of the activation force - then the nut 1 2 will be rotated, as soon as the adjustment shaft 24 is again supported by the shoulder 36 on the sleeve 28. For in that case the retention force between the sleeve 28 in the region of the edge 32 and the conical bore 30 oF screw 29 is greater than the retaining friction on nut 12. As the sleeve 28 is prevented from rotation relative to screw 29, then due to the pin 34 gripping the longitudinal slits 35 the adjustment shaft 24 is also prevented from rotating. By the rotation of nut 12 thus achieved screw 1 5 is screwed out in the direction towards the brake disc 3 and thus the adjustment process has been automatically carried out.

To adjust the clearance "L" a grub screw 37 is first loosened and following this the screw 29 freed thereby is turned through a greater or lesser distance. A cap 38 protecting the bore 25 of brake saddle 1 against entry of dirt has to be removed first.

In Figure 4 the grub screw 37 with the threaded bore which receives it is illustrated rotated through an angle of 90 .

Claims

1. Adjustment mechanism for the automatic compensation of brake lining wear of a disc brake having a brake saddle which is mounted on a brake carrier for displacement transversely to the brake disc and embraces with its two shanks the brake disc as well as two brake lining carriers arranged on each side of the brake disc, and a brake activation mechanism for engaging the biake lining carriers in the direction of a brake disc against the action of a return spring, characterized in, that the engagement of the brake lining carriers is achieved by means of a screw and a nut, which on its exterior has a helical gear, that an adjustment shaft which is mounted in a bore transverse to the direction of displacement of the nut, has a helical gear which engages the helical gear of the nut, and that the adjustment shaft is axially displaceable in a clearance range "L" which corresponds to the release clearance of the brake on its activation and that on wear of the lining the adjustment shaft is adapted to be temporarily rotated by an amount corresponding to the degree of wear while overriding a frictional anti-rotation lock.

2. Adjustment mechanism according to claim 1, characterized in that the adjusting shaft is rotationally fast with a sleeve acted upon by a spring, which abuts a conical bore which has a predetermined position relative to the brake saddle with a projecting edge formed on a radially projecting shoulder of the sleeve.

3. Adjustment mechanism according to claim 2, characterized in that the sleeve is connected for rotation with the adjusting shaft by a pin which passes transversely through the adjusting shaft and whose ends engage in longitudinal slits of the sleeve.

4. Adjustment mechanism according to claims 2 or 3, characterized in that the clearance "L" is adjustable by adjustment of the position of the conical bore in relation to the brake saddle.

5. Adjustment mechanism according to claim 3, characterized in that the conical bore is provided in a screw by rotation of which the clearance "L" can be adjusted.

6. Adjustment mechanism according to claim 5, characterized in that the adjusting shaft with its end carrying the sleeve passes through the conical bore of the screw and that between the end of the sleeve and the screw there is interposed a compression spring.

7. Adjustment mechanism according to claim 6, characterized in that the helical compression spring surrounds the sleeve, and with one end abuts screw and with its other end is supported on a snap-ring mounted on the sleeve.

8. Adjustment mechanism substantially as hereinbefore described with reference to the accompanying drawings.