GB2098682A - Disc brake actuator mechanism - Google Patents

Abstract

In a vehicle disc brake actuator mechanism an actuator 1 has its output rod 2, 22 pivotally connected to a lever 13, 23 incorporating an automatic slack adjuster, said lever 13, 23 being drivingly mounted on a shaft 5, 25 carrying one or more shorter levers 7 (Figure 1) or cams 31 (Figure 2) for converting the rotary motion of the shaft into linear motion of one or more push rods 8, 33a, 33b to transmit brake force to one or more disc brake pads. Actuator 1 may be combined service brake and spring brake actuator. <IMAGE>

Description

SPECIFICATION Disc brake actuator mechanisms This invention relates to disc brake actuator mechanisms.

It would be conveninent from the point of view of manufacturing costs if a common type of brake actuator could be emplqyed for disc brakes as well as for conventional drum-type foundation brakes.

One form of disc brake actuator mechanism which has been proposed with this in mind is described in the specification of co-pending Patent Application No. 8037650 wherein a brake actuator has a brake force output member operable through the arm of a lever to apply a magnified force to a brake stator for operating brake pads or shoes, the lever being connected to the stator via linearly operable means to maintain a predetermined pad or shoe clearance and the actuator being connected to the lever via a oneway clutch mechanism whereby the actuator is permitted to return to a given fully returned position after each brake application. The convenience of the above mentioned mechanism could be increased upon even further if the mechanism could make use of a commonly available automatic slack adjuster mechanism for maintaining the predetermined pad or shoe clearances.

According to the present invention a vehicle discbrake actuator mechanism having a fluid pressure operable actuator having a force output member pivotally connected to a lever incorporating a slack adjuster said lever being drivingly mounted on a shaft journalled in a chassis or vehicle axle member said shaft carrying one or more further shorter levers or cams to convert rotary motion to the shaft into linear motion of means to apply force to one or more disc brake pads.

In order that the invention may be more clearly understood and readily carried into effect, the same will be further described by way of example with reference to the accompanying drawings of which: Fig. 1 illustrates in diagrammatical manner a disc brake mechanism wherein a rotary motion is converted into a linear motion via a short lever and, Fig. 2 illustrates an alternative embodiment wherein the rotary motion is converted into linear motion by cam means.

Referring to Fig. ia a commercially available com- bined service brake and spring brake actuator is denoted by reference 1, the output rod 2 of this actuator being connected to the outward end 3 of a brake lever 13 incorporating an automatic slack adjuster and mounted to operate a rotary shaft 5 about an axis at 4. The shaft 5 is journalled in spaced bearings provided in a bearing block 5 mounted to the vehicle axle and spaced axially along the shaft 5 from the lever 13 there is a shorter lever 7 the end of which is connected pivotally via a link (not shown) to the outward end of a linearly moveable push rod 8 slideably carried in the bearing block. The outward end 9 of the rod 8 carries a force spreader member 10 for actuating the brake pads or shoes into engagement with the disc of the disc brake.

The lever 13 is in the form of a commercially available lever embodying an automatic slack adjuster which enables the system to operate whilst maintaining a pre-determine clearance (i.e., free movement of the actuator rod 2 before the brake force is established between pads and disc). In the arrangement shown the slack adjuster requires the provision of an actuating link as seen dotted at reference 11 coupled in known manner between a small adjustment lever on the side of the slack adjuster and an outward extension of the actuator rod at 12.

Since the lever 3 is spaced along the rod 5 from the short lever 7, the angular position thereof in relation to the bearing block 6 can be determined according to whatever the requirements of the vehicle builder may be. For example, instead of being shown with the axis of the rod 2 parallel to the axis of the rod 8, the actuator 1 may be reorientated into a position such as shown by the broken outline 14 or virtually any other angular position around the axis 4. This makes the arrangement particularly adaptable.

In operation, whatever the orientation for the lever 3 which is determined by the vehicle builder, upon operation of the brake actuator 1, the rod 2 moves until the fixed clearance is taken up whereupon the clockwise rotary motion imparted to the shaft 5 is transmitted via the small lever 7 and the mentioned pivotted link to the rod 8 to apply amplified braking force from the actuator to the force spreader 10.In the event of more than a pre-determined movement of the lever 3 occurring before a sensible braking force is encountered by the spreader 10, this is sensed by the automatic slack adjuster acting in co-operation with the link 11 and on the return movement of the lever 3, the mechanism returns to a rest position wherein the short lever 7 is appropriately adjusted for starting position in relation to the lever 3, the lever 3 always returning to its same original starting position.

Although in Fig. 1 only a single rod 8 is shown the shaft 4 may, if required, be provided with a further lever spaced from lever 7 to actuate a further such rod connected to spreader 10 or a further spreader spaced therefrom around the disc of the disc brake.

Referring now to Fig. 2, whilst the actuator itself is now shown, the outward end 22 of an actuator rod is shown connected to the end 23 of a brake lever 24 which incorporates an automatic slack adjuster and operates in the same way as the lever 3 of Fig. 1. It therefore also requires an actuating link 31 connect in an adjuster lever to extension 32 of the actuator rod. Instead of the force being transmitted to a spreader such as 10 in Fig. 1 by a short lever such as 7, a pair of triangular crank members 27a and 27b are provided pivotted at 28a and 28b in the bearing block 29 again mounted to the vehicle axial.The inward corners of members 27a and 27b have respective cam follower rollers 30a and 30b bearing against cams provided by diametrically opposed cam surfaces 31a and 31b of a S-cam 31 carried on a The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

shaft 25 which like the shaft 5 of Fig. 1 is journalled in the bearing block and driveable by the lever 23. The outward corners 32a and 32b of the 27a and 27b respectively carry rollers which engage with respective push rods 33a and 33b carrying a force spreader or spreaders which are now shown.

In operation of the apparatus shown in Fig. 2, rightward movement of the end 23 of the lever 24 by the actuator causes corresponding rotation ofthe cam 31 thereby causing respective anti-clockwise and clockwise rotation of members 27a and 27b to actuate the push rods 33a and 33b to apply braking forces.

In the event of more than a pre-determined clearance being required to be taken up by the movement ofthe lever 23 before a sensible braking force is encountered by the push rods 33a and 33b in a given brake application, on subsequent return movement of the lever from a brake applied position towards a fully released position, the eventual rest position of the cam 31 is moved slightly clockwise in relation to the lever 23 to compensate for the excess clearance.

As in the case of the mechanism of Fig. 1, since in Fig. 2 the lever 23 can again be displaced axially along the shaft 25 from the point of action of the cam 31, the orientation of the lever 23 in its rest position and consequently also the position of the actuator, can be determined by the vehicle builder in accordance with whatever may be the requirements of the particular vehicle.

Claims (5)

1. A vehicle brake actuator mechanism having a fluid pressure operable actuator having a force output member pivotally connected to a lever incorporating a slack adjuster said lever being drivingly mounted on a shaftjournalled in a chassis or vehicle axle member said shaft carrying one or more further shorter lever or cams to convert rotary motion to the shaft into linear motion of means to apply force to one or more disc brake pads.

2. A vehicle disc brake actuator mechanism as claimed in claim 1 wherein said means to apply force to the one or more disc brake pads comprises one or more slideable members.

3. Avehicle disc-brake actuator mechanism as claimed in claim 2 wherein each said further lever is coupled via a respective pivotted link the respective slideable member

4. A vehicle disc-brake actuator mechanism as claimed in claim 2, wherein the or each cam engages a pivotted triangular crank member for operating the or each slideable member.

5. Avehicle disc-brake actuator mechanism substantially as described herein with reference to Fig. 1 of Fig. 2 ofthe accompanying drawings.