FORM 2
THE Patent Act, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION Auto adjuster for drum brake
Endurance Technologies Pvt Ltd R&D, E 93, MIDC Industrial Area, Waluj, Aurangabad, Maharashtra-431136
The following specification describes the invention

Auto adjuster for drum brake
Field of invention
The present invention relates to "Auto adjuster for drum brake" and more particularly to auto adjuster mechanism for drum brake for three and four wheelers.
Description of prior art
Vehicle brakes require periodic adjustment as the lining wears, and a number of automatic slack adjusters have been designed wherein the brake operating structure automatically compensates for such wear.
Different types of adjusters for drum brakes are currently known, adapted to ensure that in rest position the shoes of the brake are found at a predetermined and essentially constant distance from the facing drum walls, so that the shoes move a constant travel, also following partial wear thereof over time. The slack adjuster is mounted between the shoes and follows their spreading movement, being lengthened during the braking step and shortened during the subsequent return movement of the shoes.
When, due to wear, the shoes become thinner and their stroke against the walls of the drum tends to increase beyond a certain predetermined threshold, the adjuster automatically adjusts the rest position of the shoes, reaching a more extended rest position as a function of the achieved state of wear.
However, for braking systems employing parking brake system, a lever type ratchet adjuster is provided with a large lever and a small latch that is further attached to a ratchet mechanism. This mechanism moves the brake shoe outward to take up excess clearance when the brakes are applied such that when the parking brake is

applied (figure 3), a cam located at the other end of the lever pushes a strut body towards opposite side due to the cam movement and the parking brake is applied accordingly. When the parking lever cam is actuated, it directly pushes the trailing shoe. As a result, the trailing brake is actuated first and touches the drum when the parking brake is applied and once the trailing brake touches the wall of the drum, the leading brake is actuated. Further, with regular usage, the brake shoe wears down following partial wear thereof over time and the gap between the said shoes and the drum increases. Once the gap between the shoe and the drum increases, the trailing shoe moves outwards and a ratchet mechanism moves along and locks in to make up the wear developed on the brake shoe.
However, this configuration of the parking brake along with the auto adjustment mechanism is quite complicated and the brake force generated on the trailing shoe is substantially more than on the leading shoe. Moreover, the available system in the prior art on the auto adjusting mechanism, servicing and replacing various parts is quite difficult. Also, a possibility exists,on over adjustment due to opening of trailing and locking at the open condition. Further, with a single pivoting, imbalanced force applied over the lever can result in bending as well as non-uniform pressure on the brake shoe. Additionally, with the resting of the trailing brake shoe on the strut plate and leading brake shoe on the cam (Figure 4), high scope of lifting of component is present.
Hence to obviate the lacunae in the prior art the object of the present invention is to provide an automatic adjustor of improved, reliable type, with simplified structure and limited production costs.

Brief description of the present invention
In one of the aspects of the present embodiment, an adjuster is provided which comprises an adjusting and holding mechanism, a strut body, a bracket preferably of U type, welded to the said strut body, a parking brake actuating lever locater, a leading shoe resting area on the said bracket. The adjusting and holding mechanism further comprises a ratchet, a ratchet holding spring and a pinion.
In the second embodiment of the present invention, an integrated strut body provided with an extension on the lateral side of said strut body and further folding it suitably creates a support for the pivot pin. The functional accuracies are maintained since the entire structure is made in single sheet and controlled pressing process.
Brief description of the drawings
The invention will be described in further detail below, reference being made to the accompanying drawings, in which:
Figure 1 illustrates the parking brake and auto adjustment mechanism according to the prior art.
Figure 2 illustrates the parking brake and the strut according to the prior art.
Figure 3 illustrates the working of the parking brake and adjustment and holding mechanism according to the prior art.
Figure 4 illustrates the parking brake and auto adjustment mechanism according to the present invention.
Figure 5 illustrates the parking brake and the strut according to the present invention.

Figure 6 illustrates the exploded view of parking brake and the strut according to the present invention.
Figure 7 illustrates one embodiment of the present invention with a U bracket welded.
Figure 8 illustrates the auto adjuster with the parking take according to the present invention.
Figure 9 illustrates second embodiment of the present invention.
Figure 10 illustrates assembly of the auto adjuster as Second embodiment according to the present invention.
Detailed description of the invention
A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1, 2, 3,4, 5, 6, 7, 8, 9 10. A parking brake lever of the general type concerned for three and four wheelers is well known in the art. It constitutes a connection level- in a brake system of a three and four wheeler between a push rod of a brake cylinder and a parking brake actuating lever 1 connected to a drum brake arrangement 2 comprising a brake drum 3 and brake shoes to be pressed together by movement of a strut 6 for braking arrangement with the brake drum 3. As shown in figure 1, a drum brake system 2 is made up of a pair of brake shoes 4 & 5 that is a leading shoe 4 and a trailing shoe 5, a wheel cylinder 7, an anchor portion 8, an adjuster 9, and a parking brake mechanism 10. The leading 4 and the trailing 5 shoes are oppositely disposed in the inner space of a cylindrical brake drum 3. The wheel Cylinder 7 is disposed between one ends of the paired brake shoes 4 & 5 and presses those ends of the brake

shoes against the brake drum 3. The anchor portion 8 supports the other ends of those brake shoes 4 & 5 and receives an anchor counter force from those brake shoes 4 & 5. The adjuster 9 is disposed along the wheel cylinder 7 between the one ends of the leading and trailing shoes 4 & 5. The adjuster 9 is disposed along the wheel cylinder 7 and between the one ends of the leading and trailing shoes 4 & 5. Functionally, it adjusts a distance between the brake shoes so that clearances between the leading shoe 4 and the brake drum 3 and between the trailing shoe 5 and the brake drum 3 are not varied at the time of braking even when the wearing of the brake shoes progresses. The parking brake mechanism 10 presses the brake shoes 4 & 5 against the brake drum 3 when a driver operates a parking lever located near to the driver seat. The leading and the trailing shoes 4 & 5 are mounted on a backing plate (not shown) by shoe hold down devices such that those brake shoes 4 & 5 are movable toward the inner circumferential surface of the brake drum 3.
The ends of the brake shoes 4 & 5 which are located closer to the wheel cylinder 7 are urged, by a shoe-to-shoe spring 11, in the directions in which those ends come nearer to each other (viz., move apart from the drum inner surface). The anchor portion 8 is fastened to the backing plate 12. The ends of the brake shoes 4 & 5 are located closer to the anchor portion 8, are mutually coupled to each other by means of an anchor spring (not shown) and urged to be in contact with the anchor portion 8.
One end of the adjuster 9 is brought into engagement with the leading shoe 4. Another end of the adjuster 9 is brought into contact with the trailing shoe 5. The adjuster lever 14 rotates with an expanding motion of the leading shoe 4 that is caused at the time of braking. With progress of wear of the lining of the brake shoes, the adjuster lever 14 turns the adjuster 9, so that a distance between the brake

shoes 4 & 5 is automatically adjusted so as to maintain appropriate clearances each between the lining of each brake shoe 4 & 5 and the drum 3.
In one of the aspects of the present embodiment, an adjuster 9 is provided which comprises an adjusting and holding mechanism 15, a strut body 6, a bracket 16 preferably of U type, joined to the said strut body 6 preferably through welding or riveting, a parking brake actuating lever locater 17, a leading shoe 4 resting area on the said bracket 18. The adjusting and holding mechanism 15 further comprises a ratchet 19, a ratchet holding spring 20 and a pinion 21.
Once the parking brake is applied through the parking brake lever 1, the force gets transferred to the other end of the parking brake lever via a pivot point 22. The U type bracket 16 which is welded to the strut body 6 supports the parking lever pivot pin 23 at the two ends which overcomes the force imbalances as compared to earlier design and lateral reactions on parking lever 1. Further, owing to the construction, the pivot pin 23 is supported at two ends and transfers a uniform pressure on the brake shoe. Consequently, the said other end of the parking brake lever 1 pushes the leading brake shoe 4. As a result, the force via said pivot point 22 gets transferred to said strut body 6 and pushes the trailing brake shoe 5. This initiates the actuation of the parking brake and the vehicle stops. The said adjusting and holding mechanism 15 maintain the designed gap between the trailing shoe 5 and brake drum 3 depending on the wear of the brake shoe 5. As the brake shoe wears, the cam shaped ratchet 19 rotates relative to pinion 21 and adjusts the gap between the brake shoe 5 and brake drum 3 by increasing effective strut span. Ratchet holding spring 20 keeps the ratchet 19 and pinion 21 in engaged condition for its functioning.

In the second embodiment of the present invention, an integrated strut body 6 provided with an extension on the lateral side 24 of said strut body 6 and further folding it suitably creates a support 25 for the pivot pin 23. The functional accuracies are maintained since the entire structure 9 is made in single sheet and controlled pressing process.
Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.

Claims: We claim:
1. An auto adjuster for a drum brake, having a brake drum and at least two braking shoes, with a parking lever for three and four wheelers comprising an adjusting and holding mechanism, a strut body, a bracket, a parking brake actuating lever locater and a brake shoe resting area.
2. The auto adjuster for said drum brake with a parking lever for three and four wheelers as claimed in claim 1, wherein said adjusting and holding mechanism comprises a ratchet, a ratchet holding spring and a pinion.
3. The auto adjuster for said drum brake with a parking lever for three and four wheelers as claimed in claim 1, wherein said bracket is of U type joined to the said strut body.
4. The auto adjuster for said drum brake with a parking lever for three and four wheelers as claimed in claim 1, wherein when the brake shoe wears, said ratchet rotates relative to pinion and adjusts the gap between said brake shoe and said brake drum.
5. An auto adjuster for a drum brake, having a brake drum and at least two braking shoes, with a parking lever for three and four wheelers comprising an adjusting and holding mechanism, a integrated strut body with an extension on the lateral side of said strut body, a parking brake actuating lever locater and a brake shoe resting area.
6. The auto adjuster for said drum brake as claimed in claim 5, wherein when said lateral side extension on the said strut body is suitably folded, creates a support for a pivot pin for said parking lever.

7. The auto adjuster for said drum brake with a parking lever for three and four wheelers as claimed in claim 5, wherein said adjusting and holding mechanism comprises a ratchet, a ratchet holding spring and a pinion.
8. The auto adjuster for said drum brake with a parking lever for three and four wheelers as claimed in claim 5, wherein when the brake shoe wears, said ratchet rotates relative to pinion and adjusts the gap between said brake shoe and said brake drum.
9. An auto adjuster for a drum brake with a parking lever for three and four wheelers as herein substantially described and illustrated with reference to the accompanying drawings.