GB2092247A - Disc brake actuator mechanism - Google Patents

Abstract

A disc brake actuator mechanism has a spring and pneumatic actuator 1 with an output rod (3) which engages the end (4) of an arm of a lever (5) via a one-way clutch mechanism (6), the lever having a journal (13) and a pivot point (8) for connection to a rod (9) for applying a magnified force to a disc brake stator to apply pads to a disc, and a second one-way clutch arrangement (12) permitting a predetermined amount 'C' of return movement to determine a fixed brake clearance. The one-way clutch mechanism (6) comprises spring loaded rollers between rod (3) and the surfaces of wedge-apertures. The arrangement (12) has spring loaded rollers (33) housed in wedge apertures (35) in a slidable block (31), and a friction member (36) engaging rod (9). Block (31) is carried distance 'C' before block (31) is arrested following which rod (9) moves through roller (33). <IMAGE>

Description

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

It would be convenient from the point of view of manufacturing costs if a common type of brake actuator could be employed for disc brakes as well as for conventional drum type foundation brakes and one object of the present invention is to provide a mechanism whereby this can be achieved.

According to the present invention there is provided a disc brake actuator mechanism including a brake actuator having 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 one-way clutch mechanism whereby the actuator is permitted to return to a given starting position after each brake application.

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 Fig. 1 of the accompanying drawings which illustrates in part sectional manner a disc brake actuator mechanism in accordance with one embodiment of the invention and Figs. 2a, 2b, 3 and 4 show'further details.

Referring to Fig. 1 a combined spring brake and automatic service brake actuator is represented at 1 and this has a threaded output rod 2 for applying the force of the actuator to a rod 3 of square section and internally threaded to adjustably receive the rod 2. The rod 3 is connected to the end 4 of an arm of a lever 5 via a one-way clutch mechanism denoted by reference 6 to be described in greater detail hereafter. The lever 5 is journalled at a point 1 3 which together with the actuator 1 is mounted on the chassis of a vehicle.

A pivotted link 7 is provided the end 8 of which is pivotted to a point of the lever 5 between the journal 6 and the end carrying the one-way clutch.

The other end of the link 7 is connected pivotively to an inboard end of output means in the form of a rod 9 which is connected to a force applying spreader member 10 acting on a disc brake stator not shown.

Also located in relation to the vehicle chassis at the pivot journal 13 is a guide part 13 which has a bore 11 within which the rod 9 is slidingly guided and a second one-way clutch arrangement denoted generally at 1 2 carried in 1 3 is designed to also provide for a predetermined fixed clearance 'C' between the disc brake pad and the disc itself.

Referring to the one-way clutch arrangement 6, it will be seen with the aid of the views in Fig. 2a, 2b which show enlarged part sections of the first one-way clutch used in fig. 1, that this clutch is provided by a cylindrical member 21, which is journalled in the end 4 of the lever 5 and splay slots 22 on each side of the lever 5 permit rotary movement of the rod 3 within the end 4 of the lever when retained therein by the one-wav clutch.

The one-way clutching action is provided by virtue of (a series of) four lightly spring loaded locking rollers 23 retained in wedge-apertures 25. The arrangement is such that upon movement of the rod 3 in the direction of the arrow 26, since the depth of the slots reduces for points along the direction of actuator action and the rollers 23 are firmly trapped between the respective surfaces of the rod 3 and the slots, positive driving engagement is therefore provided between the rod 3 and the end 4 of the lever 5. In contrast, upon any tendency for return movement of the rod 3 relative to end 4 the rollers 23 tend to be drawn into deeper parts of the slots and the rod 3 is therefore permitted to slide through the cylindrical member 21 permitting the actuator to return to its initial starting position whatever the amount of travel which has been required to effect a brake application.

Referring now to the second one-way clutch 12, as seen in Fig. 3, this is also provided by a small cylindrical sliding block 31 slideable in a cylindrical aperture 32 in the member 10, the amount 'C' of travel permitted for the block 31 determining the pre-determined clearance for the disc brake. The rod 9is ground with four flat faces which again slide through an arrangement of four rollers denoted by reference 33 spring loaded by a housed spring 34 into wedge apertures 35 in the slideable block 31 which are similar to apertures 25 of Fig. 2b. Furthermore, a friction member 36 is provided retained in between the block 31 frictionaily engaging the rod 9 whereby on initial movement of the rod 9 during a brake application, block 31 is carried the fixed distance 'C' within the member 10 before the block is arrested in 10 following which the rod 9 moves through the rollers 3. Both the one-way clutch 6 and the second one-way clutch 1 2 are provided with release means operable externally thereof to unseat the rollers for initial resetting after fitment.

of a replacement actuator or the blocking of the brakes respectively.

In the case of the one-way clutch 6, the release is provided for by an annular member 27 which by insertion of a screw driver or similar tool to operate a yoke 28 can be effective to unseat the rollers 23 from between the rod 3 and wedge apertures 25.

In the case of the one-way clutch 12, a similar annular member 37 is provided and in this case it is actuable by rotation of two diametrically opposite eccentric cam devices such as 38 by turning thereof by means of a suitable screw driver.

In operation of the disc brake actuator mechanisms which are described in the foregoing, on operation of the actuator 1 to apply the disc brake the rod 3 is driven in the direction of the arrow 26 and by virtue of operation of the oneway clutch 6, this movement is translated into a rotary movement of the lever 5 about the centre of the pivot bearing at 6. The force transmitted via 3 is therefore applied with the mechanical advantage of the lever 5 to the pivotted link 7 for transmission to the rod 9 and the stator through the member 10. Assuming that the predetermined clearance exists between the stator pads and the rotor disc (not shown), this will correspond to the movement of the block 31 within the member 10.

Any further movement will be permitted by virtue of the friction of member 35 being overcome and on return stroke, the block 31 will return through a movement corresponding to the pre-determined clearance 'C' before the rollers 33 provide locking of the one-way clutch whereupon the movement of the lever 5 is arrested and the rod 3 returned by virtue of free movement of the rod 3 through the one-way clutch 6.

It will be seen from the foregoing that with progressive wear of the disc pads, the end 4 of the arm 5 will return to a fully released position which progressively moves outwardly from the actuator 1 along the rod 3 thereby adjusting automatically for the wear and permitting a fixed clearance to be maintained at the disc pad by virtue of the oneway clutch arrangement 12.

It is envisaged that an arrangement such as described in the foregoing will be provided for each of two pads arranged to act in the same direction against a brake disc. It will therefore be appreciated that for each wheel axle fitted with disc brakes four such mechanisms may be incorporated to provide for the full braking force for the wheels of that axle. Alternatively, it will be understood that assuming that sufficient room exists under the vehicle chassis and that sufficient stroke is provided in brake actuators such as 1, it may be arranged that the lever 5 could be arranged with connections to two links such as 7 thereby permitting operation of two stators by one actuator.Further, it is envisaged that with a sufficiently large actuator the lever 5 may be further adapted to have an extension whereby it could be connected also to rods for actuating disc brake stators on both sides of the vehicles.

In order to reset the mechanism prior to the insertion of replacement stator pads for the disc brake, the respective release members 27 and 37 are actuated at the same time and the end 4 of lever 5 is moved manually along the rod 3 as far as possible towards the body of actuator 1. The members 27 and 37 are then freed and after replacing the stator pads and making a few dummy applications to set the clearance 'C', the mechanism is ready to recommence normal operation.

Whilst the clutch arrangements 6 and 12 are shown with different manners of release they may in practice be provided with virtually identical manners of release and as many common components as possible.

Although the invention has been described specifically in relation to actuators of disc brakes -the-invention is not intended to be limited to any particular such type of brake.

Claims (8)

1. A disc brake actuator mechanism including a brake actuator having 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 brake clearance and the actuator being connected to the lever via a one-way clutch mechanism whereby the actuator is permitted to return to a given starting position after each brake application.

2. A disc brake actuator mechanism as claimed in Claim 1, wherein the output member comprises an actuator rod and said one-way clutch mechanism comprise means carried by the arm of the lever for gripping the rod for transmitting actuator force to the arm of the lever in a brake applying direction.

3. A disc brake actuator as claimed in Claim 1, a point in the arm of the lever being connected via a pivotted link to an output means connected to the brake stator, the output means having a point which is slideable through further one-way clutching mechanism carried in a guide member located at the fulcrum of the lever.

4. A disc brake actuator as claimed in Claim 3 wherein said further one-way clutching means being such as to permit a predetermined amount of return movement to determine a fixed brake clearance.

5. A disc brake actuator mechanism as claimed in Claims 1, 2, 3 or 4 wherein the or each one-way clutch mechanism comprises a block having a wedging aperture through which the respective member passes and at least one locking element urged between the member and the wall of the wedge aperture to permit relative movement of the member through the block only in one direction.

6. A disc brake actuator mechanism as claimed in Claim 5, the respective member being a rod of square section with four such locking elements, one for each flank of the rod.

7. A disc brake actuator mechanism as claimed in Claims 5 or 6, release means being provided for urging the or each locking element away from engagement between the respective member and the wedging aperture.

8. A disc brake actuator mechanism substantially as described herein with reference to Fig. 1 or Fig. 1 and Figs. 2 and 3 of the accompanying drawings.