FIELD OF INVENTION

This invention relates essentially to the art of disc brakes. In particular the invention relates to a mechanism for providing a retainer means for the adjuster drive, when the disc brake manual adjuster drive needs to be accessible during service.

BACKGROUND OF THE INVENTION

Many brakes, for use on a vehicle, have an adjuster mechanism to set the position of friction elements to account for wear thereof. The disc brake is a brake for a wheel which reduces the rotational speed of the wheel by pushing brake pads against a brake disc to cause friction. The brake disc rotates corresponding to the wheel and/or axle. To stop the wheel, brake pads are mounted on a brake caliper and these are forced against both sides of the disc.

The manual adjustment shaft is a part of an adjustment mechanism, used to control the position of the brake pads in relation to the brake disc. As the lining of the brake pad wears away, the position of the brake pads in relation to the brake disc is automatically adjusted, by means of the adjustment mechanism. Hereby the distance between the lining material and the brake disc is kept more or less constant. The amount of rotation of the adjustment shaft is correlated to the distance that the adjuster mechanism advances the brake pads towards the brake disc. Thus the rotation of the adjustment shaft is an indicator of the wear of the brake pads of the disc brake when worn brake pads are to be replaced by new brake pads, the adjustment mechanism and thus the adjustment shaft is brought back to a starting position. This is done to give space for the new thicker brake pads.

The starting position is dependent on the thickness of the brake disc and is due to the wear of the disc. Thus the starting point is used to monitor the wear of the brake disc. Generally, the adjuster mechanism has an adjuster shaft of which an end portion is accessible from the exterior of a brake housing and operable to manually re-wind or de-adjust the adjuster to permit removal and replacement of brake friction elements (commonly known as brake pads) and/or other servicing procedures. In conventional adjuster mechanisms having such a de-adjustment facility, there is a danger of excessive manual adjustment and/or de-adjustment of the mechanism ieading to locking together, shearing, or other damage to internal components thereof, resulting in the mechanism becoming inoperative in normal use.

In prior art attempts have been made to solve this problem by providing a weakness or rupture in the adjuster shaft of such a mechanism so that shearing takes place at a predietermined excessive torque applied to the shaft in the de-adjustment and adjustment direction. This is disadvantageous in that the sheared shaft has to be replaced, requiring stripping and re-building of the adjuster after each shaft shearing.

Another solution known in prior art is to provide a shearable or deformable element engageable with the shaft. The element shears or deforms when a torque above a pre-determined torque is applied (but less than the torque that damages the adjuster mechanism), so as to prevent or reduce further torque application to the shaft. However, this arrangement requires that the element be replaced after the element has deformed or sheared.

Although many methods and arrangements reliably prevent an overloading and damaging of the adjustment device and of the brake, the adjusting shaft as a whole is simultaneously also rendered useless in all these prior art.

In some prior art, in the wear adjustment device, the head part is constructed as a separate component and, in the axial direction of the adjusting shaft as well as with respect to the adjusting shaft can non-rotatably indirectly or directly be coupled with the latter and is equipped with a desired breaking point which, when a maximally permissible torque is exceeded, results in a shearing-off of the section coupled with the adjusting shaft with respect to the section facing away from the adjusting shaft.

The present invention, on the one hand, avoids the disadvantage of the destruction of or damage to the adjusting shaft in the event of the application of an unacceptably high torque, but also achieves, on the other hand, the protection of the head part also of the adjusting shaft.

The brake disc (rotor) is attached to or rotates with the wheel against which the brake pads are applied, these brake pads are typically designed to transmit high friction forces. Depending on the materials used of the pad and the disc, shape, configuration and manner of usage, it is obvious that both brake pad and the brake disc will wear, though the rates may vary - requiring the necessity to adjust the brake to replace the pads and/or disc. Added to this, the separate component adjusting drive attached to tip of
the adjusting shaft, due to its falling off and separating away from the adjustment shaft causing damage to the working of the adjustment device is attempted to be prevented. None in the prior art have addressed problems suffered in this portion of brake wear adjuster mechanism. The solution as per invention is accomplished by adding a retainer ring to the cover plate so that the adjusting drive is maintained in the same relation to the adjusting shaft.

Such manual adjuster shafts typically include a drive adjuster formation, in the form of adjuster drive / head. This formation is disposed within a protective shaft cap which is securely mounted to the cover plate and removable to permit adjusting rotation of the shaft by way of the drive formation.

In the prior art manual adjuster shaft caps sealingly engaged with respect to sliding caliper and the close - fit mounted shaft cap protecting the adjuster shaft from ingression of dirt, dust, water from the surrounding is not generally known.

Most of the prior art focus on

a. providing weakness or rupture portion in the adjuster shaft beyond a predetermined excessive torque applied to the shaft.

b. providing deformable portion in the adjuster shaft beyond a predetermined excessive torque applied to the shaft.

c. providing separable formation head /adjuster drive in the adjuster shaft.

d. providing shaft cap for the adjuster shaft. But none address the issues suffered due to the separable formation head /adjuster drive.

OBJECT OF THE INVENTION

None of the prior art address the issues that arise due to breakable adjuster drive fitted / coupled to the tip of the adjuster shaft, which due to its 'removability' may be lost during service operation.

The present invention aims to alleviate the problems suffered in the prior art with respect to adjuster drive head and to ensure no damage is caused by engaging securely the adjuster drive to the brake wear adjustment device housing.

DESCRIPTION OF INVENTION

The present invention provides a disc brake having a brake wear adjuster system and an adjuster system which can be used on a disc brake. The invention relates to a brake pad wear adjustment device for a disc brake and in particular for a motor vehicle, having a brake application device with a brake actuating lever. No prior brake integrates adjuster drive retaining means in the novel manner now possible by the present invention, with significant improvements in mode of operation, safety and simplicity in the structure.

The forgoing objects and advantages of the present invention will be more clearly understood when considered in communication with an accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig-1 Arrangement in prior art -Retainer rings arrangement for adjustment shall cap

Fig. 2 Arrangement in invention - Retainer rinas and cover ola'te arranaement finr Fig. 3 Exploded view of adjuster drive, retainer and adjuster cap.

Fig. 4 Sectional view of the arrangement in assembled condition.

In one embodiment, the air disc brake wear adjustment device has a brake adjusting shaft, the manual wear adjustment device being mounted in a housing of a brake and being accessible from outside the housing at the inboard end, the brake wear adjustment device comprising of an adjuster drive part that couples with the adjusting shaft, said adjuster drive part being accessible from outside the housing and permitting torque transmission to the adjusting shaft, wherein the adjuster drive part that is coupleable with the adjusting shaft and wherein the said adjuster drive part has a desired breaking point which, when a maximally permissible torque is exceeded, results in a shearing-off of a section of the adjuster drive part coupled with the adjusting shaft from a section of the adjuster drive part facing away from the adjusting shaft, a cover plate coupled to the said housing, and a L-shaped surroundingly circumferential collar frame retainer, positionable with the cover plate and adjusting drive for securing the adjusting drive to the cover plate. The adjuster drive part is generally constructed as a separate component and the adjuster drive is coupleable with adjusting shaft either directly or indirectly in an axial direction and also the adjuster drive is coupleable with adjusting shaft in a rotation resistant manner.

A person skilled in the art realizes that retainer means may have many different forms, beyond the disclosed retainer ring in conjunction with the cover plate, as long as it retains the position of the adjusting drive. Many different types of retainer means are known, but none have been exploited advantageously to couple it with the adjusting drive as disclosed in this invention.

The subject retainer ring and the cover plate provide an efficient and novei retainer means for securing a traditional adjuster drive of the adjustment shaft in a novel but simple manner.

Hence the invention provides an improved disc brake wear adjustment device to assure proper positioning of the adjuster drive in the said device, and the arrangement also additionally protects the operational components from external contamination and damage. This arrangement is fail-safe. Further this arrangement may be incorporated with no major modifications or replacements of the existing conventional brake wear adjustment device available in the market.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

WE CLAIM

1. An air disc brake wear adjustment device having a brake adjusting shaft, the manual wear adjustment device being mounted in a housing of a brake and being accessible from outside the housing at the inboard end, the brake wear adjustment device comprising of:

a. an adjuster drive part that couples with the adjusting shaft, said adjuster drive part being accessible from outside the housing and permitting torque transmission to the adjusting shaft, wherein the adjuster drive part that is coupleable with the adjusting shaft and wherein the said adjuster drive part has a desired breaking point which, when a maximally permissible torque is exceeded, results in a shearing-off of a section of the adjuster drive part coupled with the adjusting shaft from a section of the adjuster drive part facing away from the adjusting shaft,

b. a cover piate coupled to the said housing, and , c. a L-shaped surroundingly circumferential collar frame retainer, positionable with the cover plate and adjusting drive for securing the adjusting drive to the cover plate

2. The air disc brake wear adjustment device as claimed in claim 1, wherein the adjuster drive part is constructed as a separate component.

3. The air disc brake wear adjustment device as claimed in claim 1, wherein the adjuster drive is coupleable with adjusting shaft either directly or indirectly in an axial direction.

4. The air disc brake wear adjustment device as claimed in claim 1, wherein the adjuster drive is coupleable with adjusting shaft in a rotation resistant manner.

5. The air disc brake wear adjustment device as claimed in claim 1, wherein the adjuster drive and the retainer provide protection to the adjuster shaft and seal against external contamination and damage.