DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
AUTOMATIC SLACK ADJUSTER FOR HEAVY DUTY VEHICLE AXLE

Applicant:
BEML Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
BEML Soudha, 23/1, 4th Main,
Sampangirama Nagar, Bengaluru - 560 027,
Karnataka, India

The following specification particularly describes the invention and the manner in which it is
to be performed.
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] The present application claims priority from Indian provisional application no. 202041008964 filed on 02nd March 2020.

TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to a brake adjuster for a heavy-duty vehicle axle and more specifically relates to an automatic adjustment of a slack/clearance between the brake lining and the brake drum of a vehicular braking system.
BACKGROUND OF THE INVENTION
[003] The heavy-duty vehicle axle uses a manual slack adjuster that requires periodic brake adjustment and the vehicle downtime for the brake adjustment. Thus, an automatic slack adjuster is designed to eliminate periodic brake adjustment and the vehicle downtime for the brake adjustment. The automatic slack adjuster is a clearance-sensing brake adjuster that maintains optimum clearance between the brake lining and the brake drum of the braking system of the heavy-duty vehicle.
[004] Now referring to figure 1, (prior art) for the automatic slack adjuster, the ‘S’ cam (160) brake actuation with respect to lever (162) and automatic slack adjuster (210) is disclosed. The larger end (214) of automatic slack adjuster (210) is connected to the brake system of the vehicle axle (130) through lever (162) and the ‘S’ cam (160). The smaller end (212) of automatic slack adjuster (210) is connected to a push rod (122) of the brake chamber (120) with a clevis pin (124). The brake chamber (120) is configured to extend or retract the push rod (122) and thus, the automatic slack adjuster (210) adjust the clearance between the brake lining (136) and the brake drum (132) of the vehicle braking system (100).
[005] When the brake is applied on the wheels of the vehicle, air is directed into the brake chamber (120). This has an effect of pushing the push rod (122) and thus the angular movement of automatic slack adjuster (210) rotates the ‘S’ cam (160) through the lever (162). The ‘S’ cam (160) forces the brake liners (136) away from one another and press them inside of the brake drum (132). The friction of brake lining (136) against brake drum (132) causes braking. In this way brakes are applied on the wheels of vehicle. The friction causes wear of brake liners. This wear has effect of increasing strokes of the pushrod (122). As a result, when the pushrod (122) returns to its original rest position, the ‘S’ cam (160) does not return to its original rest position due to wear in brake linings (136). Instead, the ‘S’ cam (160) rotates through a smaller angle to a new rest position. The ‘S’ cam (160) thus stops in a corresponding new rest position at which the brake linings (136) are maintained closer to brake drum (132) friction surface. All this results in a lack of effectiveness of brake of the wheel. The automatic slack adjuster (210) maintains optimum clearance between the brake lining (136) and the brake drum (132) of the vehicle braking system (100).
[006] In heavy-duty vehicle, the automatic slack adjuster with smaller span of around 75mm can be easily implemented. However, for heavy-duty vehicles with half swing axles where space and movement restrictions are there due to its steering effort and half swing capability it is very difficult to provide automatic slack adjuster with span more than 75mm. Hence, to provide automatic slack adjuster in such heavy-duty vehicles where span is more than 75mm is a challenge.

OBJECTS OF THE INVENTION
[007] Main object of the present invention is to develop automatic slack adjuster with offset arm for heavy-duty vehicle axle having swing axle design.
[008] Another object of the present invention is to develop automatic slack adjuster with offset arm which can sustain larger forces.
[009] Yet another object of the present invention is to develop automatic slack adjuster with offset arm that take cares of steering effort and half swing axles of heavy-duty vehicles.
[0010] Another object of the present invention is to develop automatic slack adjuster with offset arm which consider the vehicle packaging of heavy duty vehicles.
[0011] Another object of the present invention is to eliminate manual intervention in adjusting the clearance between the brake lining and the brake drum of a heavy-duty vehicle axle.
[0012] Another object of the present invention is to reduce the consumption of air pressure during every brake application due to the shorter stroke of the actuator.
[0013] Another object of the present invention is to increase the safe operation of the vehicle since consistent stopping distance is maintained throughout the brake lining life.

SUMMARY OF THE INVENTION
[0014] Before the present system is described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to the automatic slack adjuster for the heavy-duty vehicle axle, and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[0015] The present subject matter described herein, in general, relates to the brake adjuster for the heavy-duty vehicle axle and more specifically relates to adjusting a slack/clearance between the brake lining and the brake drum of a vehicular braking system. The present invention discloses the automatic slack adjuster that comprises an offset arm with the predetermined length and preset spline pitch. The automatic slack adjuster is a clearance-sensing brake adjuster, that maintains optimal clearance between the brake lining and the brake drum, in addition to working as a lever to move the brake shoe to the drum, through the ‘S’ cam. The offset arm of the automatic slack adjuster is designed for heavy-duty half swing axle vehicles because the space restriction and movement restrictions are there on existing axle due to its steering effort and half swing capability.

BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing:
[0017] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0018] Figure 1 illustrates the conventional automatic slack adjuster in vehicle braking system. (Prior art)
[0019] Figure 2 illustrates the assembled view of the automatic slack adjuster in the vehicle braking system for heavy-duty vehicle axle, in accordance with one embodiment of the present subject matter.
[0020] Figure 3 illustrates left-hand side view of automatic slack adjuster for heavy-duty vehicle axle, in accordance with one embodiment of the present subject matter.
[0021] Figure 4 illustrates right-hand side of view automatic slack adjuster for heavy-duty vehicle axle, in accordance with one embodiment of the present subject matter.
[0022] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF THE INVENTION
[0023] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0024] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0025] Referring now to figure 2, in one aspect of the present invention, an automatic slack adjuster (110) for the heavy-duty vehicle axle (130) is disclosed. The automatic slack adjuster (110) is designed for heavy duty half swing axle of the vehicles because the space restriction and movement restrictions are there on existing axle due to its steering effort and half swing capability. The automatic slack adjuster (110) is a clearance-sensing brake adjuster that maintains optimum clearance between the brake lining and brake drum in addition to working as a lever to move the brake shoe to the brake drum, through the ‘S’ cam.
[0026] Referring now to figure 3, in one aspect of the present invention, left-hand side view of automatic slack adjuster (110) for heavy-duty vehicle axle (130) is disclosed. According to an embodiment of the present invention the automatic slack adjuster (110) comprises an offset arm (112) with the predetermined offset length of 143 mm and span of 275 mm. However, the offset length and span will vary according to vehicle in which automatic slack adjuster (110) with offset arm (112) of present invention is to be mounted. The two ends of the offset arm (112) of the automatic slack adjuster (110) are configured to intersect each other at a point ‘M’ at an intermediate predetermined point. The longitudinal axis of the smaller end (114) and the larger end (116) of the offset arm (112) of the automatic slack adjuster (110) are configured to be offset by a predetermined distance. The distance between the longitudinal axis of the smaller end (114) and the larger end (116) of the offset arm (112) of the automatic slack adjuster (110) is configured to vary, based on steering effort and half swing capability of the heavy-duty vehicle. The cross section area of the offset arm (112) is configured to vary along its length. The offset arm is configured with wider section at point of intersection ‘M’ of the longitudinal axis of the smaller end (114) and larger end (116) of the offset arm (112) to strengthen the offset arm (112). The larger end (116) of automatic slack adjuster (110) comprises a worm shaft (140), a worm (142), a worm gear (144), a friction lock (146) and an adjusting nut (150). The worm shaft (140), the friction lock (146) and the adjusting nut (150) co-operates to function as adjuster drive. The adjusting nut (150) is configured for initial setting of the automatic slack adjuster (110) after installing. The worm shaft (140) is configured with circular grooves (152) to lock the worm shaft (140) using friction lock (146). The worm gear (144) is configured with internal splines (148) with preset pitch. This internal splines (148) of the worm gear (144) mesh with external splines (148) of the ‘S’ cam lever (162) and creates relative motion between the automatic slack adjuster (110) and the lever (162) of ‘S’ cam (160).
[0027] When the brakes is applied on the wheels of the vehicle, air is directed into the brake chamber (120). This has an effect of pushing the push rod (122) and thus the angular movement of automatic slack adjuster (110). The worm gear (144) inside the larger end (116) of automatic slack adjuster (110) is configured with external teeth to mesh with the worm (142) on the worm shaft (140). This causes the worm gear (144) and worm shaft (140) to move relative to one another in a circumferential direction about circumference of worm gear (144). Thus, the internal spline (148) of the worm gear (144) rotates corresponding external spline (148) of the ‘S’ cam lever (162) that creates relative motion between the automatic slack adjuster (110) and the lever (162) of ‘S’ cam (160). The ‘S’ cam (160) is configured to actuate the brake liners (136) and press them inside of the brake drum (132). The friction of brake lining (136) against brake drum (132) causes braking. In this way brakes are applied on the wheels of vehicle. The friction causes wear of brake liners. This wear has effect of increasing strokes of the pushrod (122).
[0028] As a result, when brake is released, the pushrod (122) returns to its original rest position, the ‘S’ cam (160) does not return to its original rest position due to wear in brake linings (136). Instead, the ‘S’ cam (160) rotates through a smaller angle to a new rest position. The ‘S’ cam (160) thus stops in a corresponding new rest position at which the brake linings (136) are maintained closer to brake drum (132) friction surface. All this results in a lack of effectiveness of brake of the wheel. Thus the indexing of worm shaft (140) and worm gear (144) is done by friction lock (146). The friction lock (146) carries spring attached circular ball. As the worm shaft (140) rotates to a new rest position by meshing worm gear (144), the spring attached circular ball in the friction lock (146) moves to the next circular groove (152) to lock the worm shaft (140) in new rest position. In this way the automatic slack adjuster (110) maintains optimum clearance between the brake lining (136) and the brake drum (132) of the vehicle braking system (100).
[0029] In automatic slack adjuster (110) the internal stresses are developed due to the loads. The middle portion ‘M’ of arm (112) of automatic slack adjuster (110) is bent. This bending portion ‘M’ is weaker. Thus, it is necessary to increase structural strength of automatic slack adjuster (110). Strengthening of the automatic slack adjuster (110) for 143 mm offset is the challenge. The strength of automatic slack adjuster (110) is achieved through forging method.
[0030] Referring now to figure 3 and figure 4, in one aspect of the present invention,
AA = Longitudinal axis of the larger end (116) of the automatic slack adjustor (110).
A’A’ = Longitudinal axis of the smaller end (114) of the automatic slack adjustor (110).
BB = Transverse axis of the larger end (116) of the automatic slack adjustor (110).
B’B’ = Transverse axis of the smaller end (114) of the automatic slack adjustor (110).
D = Span of the automatic slack adjustor (110) = 275 mm
d = Offset length of the automatic slack adjustor (110) = 143 mm
[0031] By using the automatic slack adjuster (110) there is no need for the periodical brake adjustments and the vehicle downtime for brake adjustment is eliminated. It also reduces the maintenance cost due to the elimination of brake adjustments and less consumption of air pressure during every brake application due to the shorter stroke of actuators. It may also increase the brake lining life. It increased the safe operation of the vehicle since consistent stopping distance is maintained throughout the lining life. Brake setting with the automatic slack adjuster (110) is required only during an initial setting.
[0032] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0033] The present invention enables to automatically adjust clearance between the brake lining and the brake drum of a heavy-duty truck axle.
[0034] The present invention enables to eliminate manual intervention in adjusting the clearance between the brake lining and the brake drum of a heavy-duty truck axle.
[0035] The present invention enables to reduce consumption of air pressure during every brake application due to the shorter stroke of actuators.
[0036] The present invention enables to increase the safe operation of the vehicle since consistent stopping distance is maintained throughout the lining life.
[0037] REFERRAL NUMERALS:
Element Description Reference Numeral
Assembled view of the automatic slack adjuster in vehicle braking system 100
Automatic slack adjuster 110
Offset arm of automatic slack adjuster 112
Smaller end of the automatic slack adjuster 114
Larger end of the automatic slack adjuster 116
Brake Chamber 120
Pushrod 122
Clevis Pin 124
Vehicle axle 130
Brake Drum 132
Brake Shoe 134
Brake Liners 136
Worm shaft 140
Worm 142
Worm gear 144
Friction lock 146
Internal Spline, External spline 148
Adjusting Nut 150
Circular grooves 152
‘S’ cam 160
‘S’ cam lever 162
Automatic slack adjuster (prior art) 210
Smaller end of the automatic slack adjuster (prior art) 212
Larger end of the automatic slack adjuster (prior art) 214

,CLAIMS:
1. An automatic slack adjuster (110) for a heavy duty vehicle axle (130), comprising:
an offset arm (112) of the automatic slack adjuster (110) configured to be implemented on a half swing axle of the heavy-duty vehicle wherein the two ends of said offset arm (112) are adapted to intersect each other at a point “M” at an intermediate predetermined point;
a smaller end (114) and a larger end (116) of the offset arm (112) of the automatic slack adjuster (110) wherein the longitudinal axis of said ends are configured to be offset by a predetermined distance wherein the cross section area of the offset arm (112) is configured to vary along its length;
the larger end (116) of the automatic slack adjuster (110) is configured with a worm gear (144) to mesh with a worm (142), a worm shaft (140) and a spline (148);
a friction lock (146) with spring attached circular ball is configured to move to the next circular groove on the worm shaft (140) and locks the worm shaft (140) to a new rest position;
an adjusting nut (150) is configured for initial setting of the automatic slack adjuster (110) after installing on the vehicle axle;
a ‘S’ cam lever (162) is configured with spline to mesh with corresponding spline (148) to provide relative motion between the automatic slack adjuster (110) and the ‘S’ cam lever (162); and
at least one brake liner (136) inside of a brake drum (132) is configured to be actuated by the ‘S’ cam (160).

2. The automatic slack adjuster (110) as claimed in claim 1, wherein said distance between the longitudinal axis of said smaller end (114) and the larger end (116) of the offset arm (112) of the automatic slack adjuster (110) is configured to vary based on the steering effort and half swing capability of the heavy-duty vehicle.

3. The automatic slack adjuster (110) as claimed in claim 1, wherein said cross section area of the offset arm (112) increases in length from the smaller end (114) to the larger end (116) of the automatic slack adjuster (110).

4. The automatic slack adjuster (110) as claimed in claim 1, wherein the offset arm (112) of the automatic slack adjuster (110) is configured with a predetermined offset in a range of 120 mm to 160 mm.

5. The automatic slack adjuster (110) as claimed in claim 1, wherein as per one embodiment of the invention the offset arm (112) of the automatic slack adjuster (110) is configured with an offset length of 143 mm for a span of 275 mm.

6. The automatic slack adjuster (110) as claimed in claim 1, wherein the worm gear (144) of the automatic slack adjuster (110) is configured with external teeth to mesh with worm (142) and internal splines to mesh with the external splines (148) of “S” cam lever.

7. The automatic slack adjuster (110) as claimed in claim 1, wherein, the strength of automatic slack adjuster (110) with offset length of 143 mm is achieved through forging method.

8. The automatic slack adjuster (110) as claimed in claim 1, wherein the offset arm (112) is configured with wider section at the point of intersection ‘M’ of the longitudinal axis of said smaller end (114) and a larger end (116) of the offset arm (112) to strengthen the offset arm (112).