FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
TITLE: “BRAKE SLACK ADJUSTER”
NAME AND ADDRESS OF THE APPLICANT:
TATA MOTORS LIMITED, an Indian company having its registered office at Bombay house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra, INDIA.
Nationality: Indian
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Embodiments of the present disclosure generally relates to automotive braking systems, and more particularly embodiments relates to an automatic brake slack adjuster of an automotive braking system.
BACKGROUND OF THE DISCLOSURE
Typically, heavy commercial vehicles, such as trucks, buses and the like, employ air brakes. The air brakes conventionally include a chamber to which air is supplied while application of the brake. When the air is supplied to the chamber, a piston extends from the chamber and is connected through a linkage for rotating a cam (S-cam) which in turn expands brake shoes/lining into contact with a brake drum.
When the brake is released and the air is vented from the chamber, the piston retracts into the chamber and the cam is rotated in an opposite direction so that the brake shoes move away from the brake drum. Preferably, a predetermined clearance is provided between the brake shoes/lining and the brake drum when the brakes are released. This clearance should be uniform for all brakes of the vehicle, so that uniform braking forces are applied to the wheels on either side of the vehicle. The gap between the brake shoes/lining and the brake drum should be small, so that the piston rod extending from the air chamber needs to move only a small distance to engage the brakes. Incidentally, the risk of poor braking is avoided. However, sufficient clearance shall be provided in order to prevent the brake shoes from dragging on the drum (brake grabbing), particularly when they are hot and experiencing thermal expansion. Any drag between the brake shoes and the drum may cause various problems, such as, but not limited to, the brake noise, excessive wear on the brake shoes, over heating and excessive fuel consumption for the vehicle.
With the passage of time, the wear of the brake shoes occurs and therefore, a longer stroke of the brake piston becomes necessary before the brake is applied.

In order to avoid that, adjustment of the angular position of the brake lever relative to the S-cam shaft, may be done by manually turning a shaft of a worm screw in engagement with a worm wheel, which is attached to the S-cam shaft.
Alternatively, an automatic turning mechanism, known as automatic slack adjuster, may be employed to the brake lever for automatically turning the worm screw shaft and thus adjusting the angular position of the brake lever in dependence on the brake shoes wear.
OBJECTS OF THE DISCLOSURE
The objective of disclosure is to provide a reliable, and simple, automatic brake slack adjuster of an automotive braking system.
Another objective of the disclosure is to provide an automatic brake slack adjuster equipped with an anchor bracket and an incremental plate.
Yet another objective of the disclosure is to provide an automatic brake slack adjuster having an increased number of reference positions for adjusting gaps.
Further objects and features of the disclosure will become apparent from the following detailed description when considered in conjunction with the drawings.
SUMMARY OF THE DISCLOSURE
The various embodiments of the preset disclosure relate to a brake slack adjuster for adjusting slack between a brake shoes and a brake drum of a vehicle. The brake slack adjuster comprising: a body having a first portion connectable to a brake actuator; an incremental mechanism provided within the body, the incremental mechanism adapted to steppedly rotate an adjustment shaft based on a predefined input from the brake actuator; a control arm mounted on the body and having a toothed gear engaged with the incremental mechanism; an anchor bracket connected to the control arm and the vehicle; and an incremental plate adapted to be connected to the anchor bracket for engaging with the control arm thereby locking the control arm with respect to the vehicle at one or more locking positions.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of an automatic brake slack adjuster connected to a braking system of a vehicle, in accordance to an embodiment of the present disclosure.
FIG. 2 illustrates a partially cut-away and cross-sectioned side view of the automatic brake slack adjuster of FIG. 1 connected to the braking system of a vehicle, in accordance to an embodiment of the present disclosure.
FIG. 3 illustrates a partially cut-away and perspective view of the automatic brake slack adjuster of FIG. 1 connected to the braking system of a vehicle, in accordance to an embodiment of the present disclosure.
FIG. 4 illustrates an exploded perspective view of the automatic brake slack adjuster of FIG. 1, in accordance to an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the disclosure only, and not for the purpose of limiting the same.
FIG. 1 illustrates a perspective view of an automatic brake slack adjuster 100 (hereinafter referred as “brake slack adjuster 100”) connected to a braking system 200 of a vehicle (not shown), in accordance to an embodiment of the present disclosure. The vehicle may be a heavy commercial vehicle, such as but not limited to, a truck, a bus and the like. As would be apparent to those skilled in the art that the vehicle includes a vehicle chassis (not illustrated) carrying a set of wheels (not illustrated). Each wheel of the set of wheels is provided with a braking system, such as the braking system 200.
The braking system 200 includes a spring brake actuator 202 (also alternatively referred to as “brake actuator 202”). The spring brake actuator 202 is mounted on the vehicle chassis by a mounting bracket 204. Also mounted on the mounting bracket 204, is the brake slack adjuster 100. A connecting rod 206 (shown in FIG. 2) connects the spring

brake actuator 202 to the brake slack adjuster 100. Further, a shaft 208 extends from the spring brake actuator 202. In accordance to an embodiment of the present disclosure, the shaft 208 may be an S-cam shaft and an opposite end of the shaft 208 carries a cam, such as an S-cam 210 (shown in FIG.2). The S-cam 210 is positioned proximate to unpivoted ends of brake shoes 212. It may be apparent to those skilled in the art that as the shaft 208 is rotated, the S-cam 210 acts equally and oppositely on the brake shoes 212, to force the brake shoes 212 to expand thereby coming in frictional contact with a brake drum 214.
Referring now to FIGS. 2 through 4, the brake slack adjuster 100 includes a body 102 having a first potion 104 and a second potion 106 opposite to the first potion 104. As best shown in FIG. 2, the first portion 104 of the body 102 of the brake slack adjuster 100 is tiltably connected to the connecting rod 206 of the spring brake actuator 202. The second portion 106 of the body 102 includes an incremental mechanism 101. The incremental mechanism 101 includes a rotatable internally splined worm wheel 108 enclosed within the body 102. The internally splined portion of the worm wheel 108 threadably engages with an end of the shaft 208. A spring loaded worm gear shaft 110 is also supported within the body 102. A portion of the spring loaded worm gear shaft 110 is engaged with a portion of the worm wheel 108. In one embodiment of the present disclosure, the axis of the worm wheel 108 is mutually parallel to the longitudinal axis of the worm gear shaft 110.
The incremental mechanism 101 further includes a ratchet mechanism 112 engaged with a worm-wheel end portion 114 of the spring loaded worm gear shaft 110. Particularly, the ratchet mechanism 112 includes a geared top portion 116 selectively engaged to a worm shaft 118, the worm shaft 118 being engaged with the worm-wheel end portion 114.
A control arm 216 (best shown in FIG. 3) is mounted on the body 102 and having a toothed gear portion 218 engaged with the geared top portion 116 of the ratchet mechanism 112. Opposite end of the control arm 216 includes a tab 220. In one embodiment of the present disclosure, the tab has rectangular cross section, as visible in FIG. 1. The control arm 216 is adapted to move relate to the body 102, whereby the

toothed gear portion 218 rotates the geared top portion 116. Particularly, the geared engagement of the toothed gear portion 218 with the geared top portion 116 (best shown in FIG 2 and 3) causes movement of the geared top portion 116 when the toothed gear portion 218, but in opposite direction.
Referring particularly to FIG. 1 and FIG 4, an anchor bracket 300 is connected to the control arm 216 and the vehicle. Particularly, the anchor bracket 300 is connected to the control arm 216 and the mounting bracket 204, thereby connecting the control arm 216 to the mounting bracket 204. As per the present embodiment of the disclosure, the anchor bracket 300 is fastened to the mounting bracket 204. The anchor bracket 300 includes a rectangular slot 302 (numbered in the FIG. 4). The rectangular slot 302 is adapted to receive the tab 220 of the control arm 216. The size of the rectangular slot 302 is bigger that the size of the tab 220. It may herein be noted that the rectangular slot 302 may be of any other shape such as square, polygonal, oval or the like, depending upon the shape of the tab 220, without departing from the spirit of the disclosure. The anchor bracket 300 further includes a plurality of holes such as hole 304, and hole 306.
Further, as shown in FIG. 1 and 4, an incremental plate 308 is provided to the brake slack adjuster 100. The incremental plate 308 is adapted to be connected to the anchor bracket 300. As per the present embodiment of the disclosure, the incremental plate 308 is fastened to the anchor bracket 300 for engaging with the control arm 216 thereby locking the control arm 216 with respect to the vehicle at least one locking positions. The incremental plate 308 also includes a plurality of spaced apart through holes for locking the control arm 216 with respect to the vehicle. As per the present embodiment, the incremental plate 308 includes three pair of holes 310, 312, and 314. The holes of each pair are aligned. The pair of holes 310, 312, and 314 is positioned longitudinally offset from a longitudinal edge portion 315 of the incremental plate 308. In the present embodiment, the longitudinal offset of holes 310 from longitudinal edge portion of the incremental plate 308 is bigger than the longitudinal offset of holes 312 longitudinal offset from longitudinal edge portion of the incremental plate 308. Likewise, the longitudinal offset of holes 312 from the longitudinal edge portion of the incremental

plate 308 is bigger than the longitudinal offset of holes 314 the longitudinal offset from longitudinal edge portion of the incremental plate 308.
The space between the holes of any pair of hole is equal to the distance between the hole 304 and the hole 306. Therefore, the hole 304 and the hole 306 may be fastened to any pair of hole at a time. It may herein be noted that in alternative embodiments, there may be fewer or more number of pair of hole on the incremental plate, without deviating from the spirit of the present disclosure.
During application of brake i.e. during the pressing of the brake pedal (not shown), pressurized air is supplied to the spring brake actuator 202. The pressurized air causes the connecting rod 206 to extend in a linear direction away from the spring brake actuator 202 (shown in FIG. 2). Resultantly, the brake slack adjuster 100 rotates to turn rotate the shaft 208, thereby causing the S-cam 210 to move the brake shoes 212 into frictional engagement with the brake drum. In the same manner, when the brake pedal is released, pressurized air flows from the spring brake actuator 202 causing the connecting rod 206 to retract into the spring brake actuator 202. Because of which, the connecting rod 206 rotates the brake slack adjuster 100, the shaft 208 and the S-cam 210 to allow the brake shoes 212 to retract a predetermined distance or clearance from the brake drum.
When the brake shoe 212 becomes worn, the clearance between the brake shoe 212 and the brake drum increases and it becomes progressively necessary to rotate the brake slack adjuster 100, the shaft 208 and the S-cam 210, through a greater angle to apply the brakes properly. The brake slack adjuster 100 rotates the shaft 208 and thus the S-cam 210, so that the increase in clearance between the brake shoe 212 and the brake drum is compensated. The position of the S-cam shaft 210 may be in between a set of angular graduations. Each angular graduation corresponds to a resultant position of the brake shoes with respect to the brake drum.
As per the working of the brake slack adjuster 100, the rotation of the shaft 208 is dependent upon movement of the body 102 with respect to the control arm 216 (connected to the vehicle). Therefore, when the (angular) movement of the body 102 with

respect to the control arm 216 is beyond a predetermined limit, the shaft 208 rotates. The incremental mechanism is adapted to steppedly rotate an adjustment shaft 208 based on a predefined input from the spring brake actuator 202 and the movement of the body 102 with respect to the control arm 216. In accordance with the present disclosure, the anchor bracket 300 connects the control arm 216. The rectangular slot 302 of the anchor bracket 300 allows the control arm 216 to move therein. Further, the incremental plate 308, when connected to the anchor bracket 300 encloses a portion the rectangular slot 212. The plurality of holes on the incremental plate 308, enable the incremental plate 308 to enclose the rectangular slot 212 according to the requirement.
The foregoing description provides specific embodiments of the present disclosure. It should be appreciated that these embodiment are described for purpose of illustration only, and that numerous other alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the disclosure. It is intended that all such modifications and alterations be included insofar as they come within the scope of the disclosure as claimed or the equivalents thereof.
Referral Numerals:

Reference Number Description
100 Automatic brake slack adjuster, Brake slack adjuster
200 Braking system
202 Spring brake actuator
204 Mounting bracket
206 Connecting rod
208 Shaft
210 S-cam
212 Brake shoes
214 Brake drum
102 Body

104 First potion
106 Second potion
108 Rotatable internally splined worm wheel
110 Spring loaded worm gear shaft
112 Ratchet mechanism
114 Worm-wheel end portion
116 Geared top portion
118 Worm shaft
216 Control arm
218 Toothed gear portion
220 Tab
300 Anchor bracket
302 Rectangular slot
304 Hole
306 Hole
308 Incremental plate
310 Hole pair
312 Hole pair
314 Hole pair
315 Longitudinal edge portion

We claim;
1. A brake slack adjuster for adjusting slack between a brake shoes and a brake drum
of a vehicle, the brake slack adjuster comprising:
a body having a first portion connectable to a brake actuator;
an incremental mechanism provided within the body, the incremental mechanism adapted to steppedly rotate an adjustment shaft based on a predefined input from the brake actuator;
a control arm mounted on the body and having a toothed gear engaged with the incremental mechanism;
an anchor bracket connected to the control arm and the vehicle; and
an incremental plate adapted to be connected to the anchor bracket for engaging with the control arm thereby locking the control arm with respect to the vehicle at one or more locking positions.
2. The brake slack adjuster as claimed in claim 1, wherein the adjustment shaft is an S-cam shaft extending up to the brake shoes.
3. The brake slack adjuster as claimed in claim 1, wherein the rotation of a S-cam shaft causes movement of the brake shoes with respect to the brake drum.
4. The brake slack adjuster as claimed in claim 3, wherein the rotation of the S-cam shaft is between a set of angular graduations, each angular graduation corresponding to a resultant position of the brake shoes with respect to the brake drum.
5. The brake slack adjuster as claimed in claim 1, wherein the anchor bracket includes a slot adapted to receive a tab on the end portion the control arm.
6. The brake slack adjuster as claimed in claim 5, wherein the anchor bracket includes a pair of holes and the incremental plate includes a plurality of spaced apart through holes.

7. The brake slack adjuster as claimed in claim 6, wherein the incremental plate includes three hole pairs, the holes of each pair being aligned.
8. The brake slack adjuster as claimed in claim 7, wherein each pair of hole being longitudinally offset from a longitudinal edge portion of the incremental plate.
9. The brake slack adjuster as claimed in claim 8, wherein the incremental plate upon being connected to the anchor bracket by fastening a hole pair of incremental plate with pair of holes of anchor bracket encloses a portion of the rectangular slot.
10. The brake slack adjuster as claimed in claim 8, wherein the fastening of one of the three hole pairs of incremental plate with the pair of holes of anchor bracket locks the tab on the end portion the control arm thereby locking the control arm with respect to the vehicle at a set of locking positions.
11. A brake slack adjuster for adjusting slack between a brake shoes and a brake drum of a vehicle, the brake slack adjuster comprising:
a body connectable to a brake actuator at a first portion,
a rotatable internally splined worm wheel in a second portion of the body,
a spring loaded worm gear shaft rotatably supported within the body, the
spring loaded worm gear being engaged with the splined worm wheel, a ratchet mechanism having a ratchet portion selectively engaged with a
worm-wheel end portion of the spring loaded worm gear shaft,
a control arm mounted on the body and having a toothed gear engaged
with the ratchet portion of the ratchet mechanism,
characterized in that,

an anchor bracket connected to the control arm and the vehicle; and an incremental plate adapted to be connected to the anchor bracket for
engaging with the control arm thereby locking the control arm with respect to the
vehicle at one or more locking positions.