GB2065804A

GB2065804A - Brake Actuation Mechanism

Info

Publication number: GB2065804A
Application number: GB8039870A
Authority: GB
Original assignee: Deutsche Perrot Bremse GmbH
Current assignee: Deutsche Perrot Bremse GmbH
Priority date: 1979-12-12
Filing date: 1980-12-12
Publication date: 1981-07-01
Also published as: ATA545980A; DE2950013A1; AT384474B; IT8025645A0; FR2471514A1; GB2065804B; IT1134095B

Abstract

A brake actuation mechanism, particularly for a disc brake, comprises an actuating shaft 8 rotatable by an actuating lever 7 and formed with an eccentric lateral cut-out 10 of elongated shape and comprising at its deepest point a support surface 14 of part-cylindrical shape on which the correspondingly shaped end of a pressure piece 11 bears, which pressure piece 11 has a substantially rectangular cross-section and which engages with its other end a pressure member 12 which forms part of the force transmission path to a brake lining carrier 5' the curved support surface 14 extending substantially parallel to the shaft axis 13. The disc brake shown has the actuation mechanism allocated to one shank 4' of a displaceable brake saddle 1. Pressure member 12 abuts against a nut 17 coupled to an adjustment mechanism - nut 17 receives a screw 19 the front end of which is held in abutment on brake lining carrier 5'. <IMAGE>

Description

SPECIFICATION Brake Actuation Mechanism This invention relates to a brake actuation mechanism, in particular for a disc brake, having an actuating shaft rotatable by means of an actuating lever and formed with an eccentric lateral cut-out, in which a pressure piece engages with one of its ends and whose other end abuts against a pressure member which forms part of a force transmission path to a brake lining carrier with brake lining which on brake actuation is relatively dispiaceable against the action of a return spring.

In a known mechanism of this type (DE-AS (German Auslegeschrift) 1,036,075) the pressure piece is formed as a threaded bolt which is screwed diametrically through a spindle on the end of a lever forming part of the force transmission path and which engages with its rounded end in a suitably shaped eccentric cutout of the actuating shaft. With this form of pressure piece only relatively small forces can be transmitted, unless' a pressure piece with a relatively large diameter is chosen, which again necessitates the use of an actuating shaft having an unallowably large diameter. In an older mechanism (DE-OS (German Offenlungsschrift) 2,925,342) which foregoes the use of a pressure piece, the pressure member abuts directly with its flat front face against an evolute-shaped cam surface of the actuating shaft.With such cam actuation there is linear contact; however it is necessary to overcome not inconsiderable frictional resistance.

The invention is based on the object of so improving on the type of actuation mechanism mentioned above, that while overcoming the disadvantages of the conventional mechanisms a particularly smoothly functionning and constructionally simple and compact construction achieved.

The mechanism of the invention, in which this object has been achieved, is essentially characterized in, that the lateral cut-out of the actuating shaft is of elongated form and has at its deepest point an approximately part-cylindrical support surface which extends parallel to the axis of the shaft, and that the pressure piece has a rectangular cross-section and at its end which engages the support surface has a corresponding part-cylindrical shape. Such a mechanism is 60 to 80% more effective compared to the known one in which actuation occurs via an evolute-shaped cam surface: this results in a noticeable lowering of the actuation force necessary.Due to the surface contact achieved by this construction use of the pressure piece according to the invention allows a more compact construction compared to a construction with a pressure piece having a circular cross-section, in which substantially only point contact is possible.

From a constructional point of view a development of the mechanism of the invention has proved particularly advantageous, in which the pressure piece at its end facing the cut-out is provided with a shoe which in an axial direction projected beyond both sides of the pressure piece.

An embodiment which is very simple from a manufacturing point of view results from having the characteristic that the pressure member engaged by the pressure piece and formed as a cylindrical piston has a part-cylindrical longitudinal groove extending over its whole front face, into which groove the pressure piece engages with its suitably shaped end.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings. There is shown in: Figure 1 a side view of the brake-carrier-brakesaddle unit of a disc brake with a mechanical brake actuation mechanism, Figure 2 a section through the brake-carrierbrake-saddle unit corresponding to line Il-Il of Figure 1, and Figure 3 a view of the brake-carrier-brakesaddle unit of Figure 1 corresponding to the viewing direction B of Figure 1, and partly in section corresponding to line Ill-Ill of Figure 2.

As can be seen from the drawings, the disc brake illustrated, which comprises an actuation mechanism according to the invention, comprises a brake saddle 1 which is mounted on a brake carrier 2 displaceable relative to a brake disc 3 which is merely indicated in Figure 1 by the outline of its exterior contour. Brake saddle 1 has two shanks 4, 4' with which it embraces the brake disc 3 as well as two brake lining carriers 5, 5' on each side of the brake disc which respectively carry brake linings 6, 6'. Shank 4' of brake saddle 1 has allocated to it a brake actuation mechanism referred to generally by the reference numeral 7. This comprises an actuating shaft 8 with an actuating lever 9. As can be seen from Figure 2 in combination with Figure 3, actuating shaft 8 has a lateral cut-out 10.Cooperating with eccentric lateral cut-out 10 there is a pressure piece 11, which with one of its ends engages in cut-out 10 and with its other end abuts a pressure piece 12. Eccentric lateral cutout 10 is of elongated construction and comprises at its deepest point a part-cylindrical support surface 1 4 which extends parallel to the shaft axis 13. The pressure piece 11 has a rectangular cross-section and its end which engages support surface 14 has a corresponding part-cylindrical shape. Pressure piece 11 is provided with a shoe 1 5 at its end facing the cut-out 10 of actuating shaft 8, which shoe in an axial direction projects beyond pressure piece 11 on both sides.Pressure member 12, engaged by pressure piece 1 is formed as a cylindrical piston, and is provided with a part-cylindrical longitudinal groove 1 6 which extends over its whole front face, into which groove pressure piece 11 engages with its suitably shaped end.

On swivelling of actuating lever 9 corresponding rotation of actuating shaft 8 gives rise to a displacement of pressure member 12 in the direction of brake disc 3 by means of pressure piece 11 mounted in the eccentric cut-out 10. For this purpose pressure member 12 is guided in a bore of shank 4' of brake saddle 1. It abuts against a nut 17, which like pressure member 12 is mounted in a bore displaceable in a direction towards brake disc 3. This nut 1 7 is coupled by an external helical gearing with an adjustment mechanism which is not illustrated in detail.By means of an internal thread 1 8 nut 17 receives a screw 19 in an axially displaceable manner, the front end 20 of which screw is held in abutment on brake lining carrier 5', and this by similar means to those used for securing abutment of brake lining carrier 5 on shank 4 of brake saddle 1. For this purpose brake lining carrier 5 has on its rear a projecting pin 21 with a head 22, behind which a spring 23 engages with two shanks.

Spring 23 is itself firmly mounted in a recess of shank 4 of brake saddle 1.

The connection of brake lining carrier 5' with screw 19 is secured in a similar manner.

Approximately at the outer end of the bore of shank 4' of brake saddle 1 which bore serves for the reception and guidance of nut 17 there is fixedly positioned a snap-ring 24 for supporting an annular disc 25, on which one end of a helical spring 26 rests, whose other end is supported by nut 17.

On brake actuation by rotation of actuating shaft 8 brake lining carrier 5' with brake lining 6' is moved towards brake disc 3 via pressure piece 11, pressure member 12, nut 17 and screw 19.

Due to the reactive force generated on engagement on the brake disc such displacement of brake saddle 1 takes place that brake lining carrier 5 with brake lining 6 also come into engagement with the brake disc 3. During brake actuation the helical spring 26 is compressed. On release of the brake helical spring 26 returns nut 17 with screw 19 as well as pressure member 12 with pressure piece 11 engaging it to their initial positions. In order to provide for substantially identical release clearances in the released position of the brake, that is during travel, on both sides of the brake disc 3 independently of the degree of wear of the brake linings 6, 6' there is provided between brake carrier 2 and brake saddle 1 a mechanism which is not illustrated in detail.

Claims

1. Brake actuation mechanism, in particular for a disc brake, having an actuating shaft rotatable by means of an actuating lever and formed with an eccentric lateral cut-out, in which a pressure piece engages with one of its ends, which with its other end abuts a pressure member which forms a part of the force transmission path to a brake lining carrier with brake lining which on brake actuation is relatively displaceable against the action of a return spring, characterized in, that the lateral cut-out of the actuating shaft is of elongated form arid has at its deepest point an approximately part-cylindrical support surface which extends parallel to the shaft axis, and that the pressure piece has a rectangular cross-section and its end which engages support surface has a corresponding part-cylindrical shape.

2. Mechanism according to Claim 1, characterized in, that the pressure piece at its end facing the cut-out of the actuating shaft is provided with a shoe whtch in an axial direction projects beyond both sides of the pressure piece.

3. Mechanism according to one of Claims 1 or 2, characterized in, that the pressure member engaged by pressure piece and formed as a cylindrical piston has a part-cylindrical longitudinal groove extending over its whole front face, into which groove the pressure piece engages with its suitably shaped end.

4. Brake actuation mechanism comprising an actuating shaft formed with an eccentric lateral cut-out of elongated shape providing a curved support surface on which the correspondingly shaped end of a pressure piece bears, which pressure piece has a substantially rectangular cross-section and which engages with its other end a pressure member which forms part of the force transmission path to a brake lining carrier, the curved support surface extending substantially parallel to the shaft axis.

5. Brake actuation mechanism substantially as hereinbefore described with reference to the accompanying drawings.