FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE: “A DRUM BRAKE ASSEMBLY”
Name and Address of the Applicant:
TATA MOTORS LIMITED, Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai. Maharashtra 400001, India
Nationality: INDIAN
The following specification particularly describes the nature of the invention and the
manner in which it is to be performed.
2
TECHNICAL FIELD
[001] Present disclosure in general relates to the field of automobiles, material science
and metallurgy. Particularly, but not exclusively, the present disclosure relates to a drum
brake assembly of a vehicle. Further embodiments of the disclosure disclose a S-cam
drum brake assembly capable of generating and maintaining a coefficient of friction
ranging between 0.35 to 0.45 to reduce noise on actuation in the vehicle.
BACKGROUND OF THE DISCLOSURE
[002] Drum brake assembly is generally employed in vehicles for its easy assembling,
low manufacturing and operating costs. However, such brake assemblies are prone to
frequent wear and tear due to material limitations and temperature constrains, which may
lead to decrease in durability and failure. One other factor affecting performance of the
drum brake assemblies in the vehicle may also be noise which may be generated due to
wear and tear or due to frequency of engagement between the components. In convention,
some of the components of the drum brake assembly may be made from ferrous-based
alloys, due to which, upon physical interaction and/or engagement between such
components, a screeching/squealing noise may be generated at defined frequency or
temperature or other parameters involved therein. Such noise may create noise pollution
during operation of the vehicle and may affect commuters in the surroundings of the
vehicle.
[003] There have been several developments in the conventional field of producing the
drum brake assembly in which different configuration of components therein have been
modified to reduce generation of noise without compromising on operational efficiency.
However, such attempts in convention tend to rely on replacing the drum brake assembly
with other mechanisms involving expensive material such as carbon fiber discs, and the
like. In other cases, conventional drum brake assembly have been proposed to include
configurations such as perforations or sound absorbing material along portions of
components of the drum brake assembly, or that sensors be included for determining wear
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of liners in the drum brake assembly, which inherently increases the costs associated with
production and usage of the drum brake assembly.
[004] The drawbacks/difficulties/disadvantages/limitations of the conventional
techniques/systems explained in the background section are just for exemplary purpose
and the disclosure would never limit its scope only such limitations. A person skilled in
the art would understand that this disclosure and below mentioned description may also
solve other problems or overcome the other drawbacks/disadvantages of the conventional
arts which are not explicitly captured above.
SUMMARY OF THE DISCLOSURE
[005] One or more shortcomings of the prior art are overcome by assembly as disclosed
and additional advantages are provided through the description in the present disclosure.
[006] Additional features and advantages are realized through the techniques of the
present disclosure. Other embodiments and aspects of the disclosure are described in
detail herein and are considered a part of the claimed disclosure.
[007] In one non-limiting embodiment, a drum brake assembly of a vehicle is disclosed.
The drum brake assembly comprising a brake drum connectable to an axle of the vehicle.
The brake drum being made from a ferrous based material defined with composition (in
wt.%) comprising C in a range of 3% to 3.3%; Si in a range of 1.8% to 2.3%; Mn in a
range of 0.6%% to 0.9%; S in a range of 0.06% to 0.1%; P in a range of 0.04% to 0.1%;
Cr in a range of 0.1% to 0.33%; Cu in a range of 0.1% to 0.3%, at least one of Sn or Mo
in a range of 0.15% to 0.2%, and reminder of the composition being Fe along with
incidental elements. Further, the drum brake assembly includes a brake shoe disposable
along an inner periphery of the brake drum. The drum brake assembly further includes a
brake liner which is disposable between the brake shoe and the inner periphery of the
brake drum. The brake liner being made from a second material, and configured to engage
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with the brake drum by generating and maintaining a coefficient of friction ranging
between 0.35 to 0.45 at a temperature ranging from 50⁰C to 300⁰C .
[008] In an embodiment, the second material of the brake liner includes carbon surface
area in a range of 1.2% to 1.4%.
[009] In an embodiment, the brake liner is configured to maintain cold compressibility
between 60micro to 100micro, on engagement with the brake drum, at a pressure ranging
from 0.2 bar to 12bar, to generate and maintain the coefficient of friction ranging between
0.35 to 0.45.
[0010] In an embodiment, the brake drum defined with a microstructure including
substantially of pearlite, and combined proportion of ferrites and steadites not exceeding
6% of surface area fraction by vol%.
[0011] In an embodiment, the microstructure of the brake drum includes a graphite flake
size in a range of 3-4 microns and is predominantly A type structure.
[0012] In an embodiment, the brake drum being defined with Brinell hardness at a
braking surface to be ranging from 150 to 200 BHN.
[0013] In an embodiment, the brake liner and the brake drum configured to generate and
maintain frequency coefficient of damping ranging from 210 to 360 N s/m, on
engagement under friction.
[0014] In an embodiment, the brake shoe being made from a cast iron material, and
wherein the brake liner is operatively flush and fixed along an outer peripheral surface of
the brake shoe.
[0015] In an embodiment, the brake liner includes porosity in a range of 1.80% to 2.4%
and a Rockwell hardness ranging between 46 to 61 (in M Scale).
[0016] In an embodiment, the brake shoe is made from cast iron of SG 550/6 grade.
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[0017] It is to be understood that the aspects and embodiments of the disclosure described
above may be used in any combination with each other. Several of the aspects and
embodiments may be combined together to form a further embodiment of the disclosure.
[0018] The foregoing summary is illustrative only and is not intended to be in any way
limiting. In addition to the illustrative aspects, embodiments, and features described
above, further aspects, embodiments, and features will become apparent by reference to
the drawings and the following detailed description.
[0019] BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
[0020] The novel features and characteristics of the disclosure are set forth in the
appended description. The disclosure itself, however, as well as a preferred mode of use,
further objectives and advantages thereof, will best be understood by reference to the
following detailed description of an illustrative embodiment when read in conjunction
with the accompanying figures. One or more embodiments are now described, by way of
example only, with reference to the accompanying figures wherein like reference
numerals represent like elements and in which:
[0021] Figure 1 illustrates an exploded view of a drum brake assembly including a brake
drum, a brake shoe and a brake liner, according to an exemplary embodiment of the
present disclosure.
[0022] Figure 2 is a flowchart illustrating a method for producing the brake drum of the
drum brake assembly of Figure 1, according to an exemplary embodiment of the present
disclosure.
[0023] Figures 3a-3b illustrate an optical microscope image (100X magnification) of
microstructure of the brake drum, according to an exemplary embodiment of the present
disclosure.
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[0024] Figure 3C depicts a graphical representation comparing difference in % of noisy
stops on actuation of the drum brake assembly in accordance to the present disclosure
with conventional drum brake assembly.
[0025] The figures depict embodiments of the disclosure for purposes of illustration only.
One skilled in the art will readily recognize from the following description that alternative
embodiments of the methods illustrated herein may be employed without departing from
the principles of the disclosure described herein.
[0026] DETAILED DESCRIPTION
[0027] The foregoing has broadly outlined the features and technical advantages of the
present disclosure in order that the detailed description of the disclosure that follows may
be better understood. Additional features and advantages of the disclosure will be
described hereinafter which form the subject of the description of the disclosure. It should
also be realized by those skilled in the art that such equivalent methods/assemblies do not
depart from the scope of the disclosure. The novel features which are believed to be
characteristic of the disclosure, as to assembly and method of production and operation,
together with further objects and advantages will be better understood from the following
description when considered in connection with the accompanying figures. It is to be
expressly understood, however, that each of the figures is provided for the purpose of
illustration and description only and is not intended as a definition of the limits of the
present disclosure.
[0028] In the present document, the word "exemplary" is used herein to mean "serving
as an example, instance, or illustration." Any embodiment or implementation of the
present subject matter described herein as "exemplary" is not necessarily to be construed
as preferred or advantageous over other embodiments.
[0029] While the disclosure is susceptible to various modifications and alternative forms,
specific embodiment thereof has been shown by way of example in the drawings and will
be described in detail below. It should be understood, however that it is not intended to
7
limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure
is to cover all modifications, equivalents, and alternative falling within the spirit and the
scope of the disclosure.
[0030] The terms “comprises”, “comprising”, or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that a method that comprises a list of
acts does not include only those acts but may include other acts not expressly listed or
inherent to such method. In other words, one or more acts in a method proceeded by
“comprises… a” does not, without more constraints, preclude the existence of other acts
or additional acts in the method.
[0031] Henceforth, the present disclosure is explained with the help of figures for a drum
brake assembly. However, such exemplary embodiments should not be construed as
limitations of the present disclosure, since the assembly may be employed any type of
vehicle including passenger vehicle, light load capacity vehicles, heavy load capacity
vehicles, and among others where such need arises. Further, the vehicle is not depicted
for sake of simplicity and that the drum brake assembly of the present disclosure is
employable in any given vehicle. A person skilled in the art can envisage various such
embodiments without deviating from scope of the present disclosure.
[0032] Figure 1 illustrates a drum brake assembly (10) in accordance with the present
disclosure. The drum brake assembly (10) includes a backing plate (4) which may be
attached to supporting structures of the vehicle such as an axle, where the backing plate
(4) may be rigidly connected thereto, to induce friction upon actuation of the drum brake
assembly (10) for regulating speed of the vehicle. Further the drum brake assembly (10)
includes a brake drum (1) which is connectable to a wheel hub of the vehicle, where the
brake drum (1) is displaceable with the wheel hub of the vehicle. The drum brake
assembly (10) further includes a brake shoe (2) which may be disposable between the
backing plate (4) and the brake drum (1). The brake assembly also includes a brake liner
(3) disposable between the brake shoe (2) and the inner periphery of the brake drum (1).
The brake liner (3) is detachably connectable to the brake shoe (2) may be by means
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including but not limited to fastening, riveting, clamping, adhesive bonding, and among
other means for connecting the brake liner (3) to an outer periphery of the brake shoe (2).
For operation, the brake shoes may be symmetrically positioned about and/or along the
inner peripheral surface of the brake drum (1), while the brake liner (3) may be defined
with a profile complementary to that of the inner surface of the brake drum (1). The brake
shoe (2) and in-turn the brake liner (3) may be displaceable by actuation mechanism
(depicted however not explicitly pointed in figures) which may be either hydraulically
operable or manually operable or combination thereof, in order to suitably displace the
brake shoe (2) and in-turn the brake liner (3) for engaging with the brake drum (1). Such
configuration of the drum brake assembly (10) may be employed as a S-cam drum brake
assembly (10) in various industrial applications including employing in vehicles.
[0033] In an embodiment, during activation of the drum brake assembly (10), the brake
shoes may be displaceable relative to the brake drum (1), where such displacement of the
brake shoe (2) may engage corresponding brake liner (3) with the brake drum (1).
Engagement between the brake liner (3) and the brake drum (1) may induce friction which
may result in braking of the vehicle. In the illustrative embodiment, for such application
of braking and retardation in speed of the vehicle, coefficient of friction (μ) at an interface
of the brake liner (3) and the brake drum (1) is generated and maintained within a
predefined limit. Such predefined limit may be dependent on a number of parameters
including, surface area of contact, temperature, gap defined between the brake liner (3)
and the brake drum (1), material constraints of the brake liner (3) and the brake shoe (2),
and among others. In the illustrative embodiment, the brake liner (3) is configured to
engage with the brake drum (1) by generating and maintaining the coefficient of friction
ranging between 0.35 to 0.45 at a temperature ranging from 50⁰C to 300⁰C. In an
embodiment, such coefficient of friction between the brake liner (3) and the brake drum
(1) may be considered for variation in gap between said brake liner (3) and the brake
drum (1), where such gap may be ranging from 0.3 mm to 2.5 mm.
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[0034] Further to ensure that such coefficient of friction is generated between the brake
liner (3) and the brake drum (1), material of the brake drum (1) is selected to be a ferrous
based material, while the brake liner (3) is made from a second material. In the illustrative
embodiment, the second material of the brake liner (3) is selected such that carbon surface
area when the brake liner (3) is so produced is in a range of 1.2% to 1.4%. Such
configuration of the brake liner (3) is manufactured using the second material which
includes PTFE based binder along with other compositions which may be employed to
ensure that the brake liner (3) does not disintegrate during operation of the drum brake
assembly (10). Such PTFE based binder in the second material of the brake liner (3) is
configured to impart thermal resistance, along with other properties such as adhesion,
flammability, non-sonorous, low electrical conductivity, and among others, to render the
brake liner (3) durable and operable at low temperature as well as high temperatures. The
second material of the brake liner (3) is selected to include properties such as damping,
compressibility, porosity, hardness, and among others. The brake liner (3) includes cold
compressibility ranging from 70 to 85 micron (at 30 bar), upon manufacturing with the
PTFE based binder. Further, such cold compressibility is accompanied by porosity
ranging from 1.80 % to 2.40 %, and Rockwell Hardness (HRM) ranging from 46 to 61
when measured on M’ Scale. Further, the second material also includes low and high
frequency coefficient of damping ranging from 216 +/-10% Ns/m and 352+/-10% Ns/m,
respectively. Due to such configuration of the brake liner (3), upon engaging with brake
drum (1), the brake liner (3) is configured to generate and maintain friction with the inner
surface of the brake drum (1) and prevent crumbling and/or disintegrating due to variation
in temperature or wear.
[0035] In the illustrative embodiment, the brake shoe (2) is predominantly be made from
cast iron of SG 550/6 grade, where the brake liner (3) is operatively flush and fixed along
an outer peripheral surface of the brake shoe (2). Connection between the brake liner (3)
and the brake shoe (2) may be performed by means including, but not limited to,
fastening, riveting, adhesive bonding, clamping, and among others. In the illustrative
embodiment, the outer peripheral surface of the brake shoe (2) may be subjected to
10
polishing and/or grinding, followed by punching or piercing process to produce apertures
capable of receiving, accommodating and/or securing the brake liner (3) thereon.
[0036] In the illustrative embodiment, the ferrous based material of the brake drum (1) is
configured to complement the second material of the brake liner (3), where the ferrous
based material of the brake drum (1) is manufactured with regulated elemental
composition that may assist for reduction in generation of noise without compromising
on imparting friction when engaged by the brake liner (3). For such configuration, the
ferrous based material of the brake drum (1) is defined with composition (in wt.%)
comprising C in a range of 3% to 3.3%, Si in a range of 1.8% to 2.3%; Mn in a range of
0.6%% to 0.9%; S in a range of 0.06% to 0.1%; P in a range of 0.04% to 0.1%; Cr in a
range of 0.1% to 0.33%; Cu in a range of 0.1% to 0.3%, at least one of Sn or Mo in a
range of 0.15% to 0.2%, and reminder of the composition being Fe along with incidental
elements. In an embodiment, the incidental elements may be elements which are
unavoidable in the alloy composition and are present in minute quantities in flux, coke,
additives or impurities. There may also be a possibility of the micro alloying elements to
precipitate out and it may then become difficult to completely dissolve the precipitates in
the subsequent reheating process rendering them ineffective for precipitation
strengthening.
[0037] Figure 2 is an exemplary embodiment of the present disclosure illustrating a
flowchart depicting a method for manufacturing the brake drum (1). In the present
disclosure, mechanical properties including, but not limited to, strength, hardness, wear
resistance, and corrosion resistance may be improved without compromising some of the
properties such as formability. The brake drum (1) produced by the method of the present
disclosure includes microstructures such as graphite fakes, ferrite, steadites, and pearlite
microstructure and any other impurities having minimal proportion in microstructure
which may impart minimal to no changes in properties of said brake drum (1).
11
[0038] The method is now described with reference to the flowchart blocks and is as
below. The order in which the method is described is not intended to be construed as a
limitation, and any number of the described method blocks can be combined in any order
to implement the method. Additionally, individual blocks may be deleted from the
methods without departing from the scope of the subject matter described herein. The
method is particularly applicable to high strength wear and corrosion resistant grey cast
iron.
[0039] At block 101, molten metal of iron may be formed by melting of iron from one or
more sources. The iron may be melted in a furnace or in a crucible positioned in an oven,
where the furnace may be for example, a blast furnace, shaft furnace, air melting furnace
and vacuum furnace or the like, while the oven may be, for example, a microwave oven.
Additionally, other type of apparatus capable of melting iron and producing molten metal
may be employed without considering to limitation of the present disclosure. For melting,
a predefined quantity of iron procured from a source of iron may be employed. Also, the
predefined from iron may be procured from a mixture of plurality of iron sources [or
interchangeably referred to “sources of iron”] which may be subjected to stacking and
heating. In an embodiment, the plurality of iron sources may include steel scrap, raw pig
iron, Ferrosilicon (Fe-Si) and any other source from which substantial proportion of iron
may be obtained on melting. Here, the term “substantial” may refer to at least 90% of iron
being obtained from such plurality of sources of iron. Further, the plurality of iron sources
may be enclosed with graphitizer. In an embodiment, the plurality of iron sources may be
subjected to at least one of stacking, layering, crushing, blending, and the like, where each
of such plurality of sources may be sandwiched with layers of one another for mixing and
forming of the molten metal with substantial uniform consistency in proportion of iron,
such as at least 98% in consistency.
[0040] At block 102, the method comprises of adding alloying elements such as Cr, Cu,
and at least one Sn or Mo to the molten metal in order to produce the ferrous based
material of the brake drum (1). In the illustrative embodiment, the alloying elements such
12
as Cr is added in a range of 0.1% to 0.33%, while Cu is added in a range of 0.1% to 0.3%
and at least one of Sn or Mo is added in a range of 0.15% to 0.2%. Such addition of the
alloying elements may regulate properties of the brake drum (1). Some of such properties
of the brake drum (1) being regulated may be including hardness, strength, formability
and among others. Here, the alloying elements of Sn and Mo are selectively to be added,
where only one of Sn or Mo is added to the molten metal for producing the ferrous based
material to produce the brake drum (1). Further, to improve mechanical properties of the
casted ferrous based material to form the brake drum (1), proportion of the alloying
elements being added may be regulated. Such addition of the alloying elements may
regulate and produce mechanical properties for operation of the brake drum (1) in
conjunction with the brake liner (3) and the brake shoe (2).
[0041] . In an embodiment, introduction of alloying elements may be a combination and
a sequential addition into the molten metal. In an embodiment, mode of addition and/or
introduction of such elements may be performed by lances, conveyors and the like that
may be adequately necessary for the apparatus, for melting of the sources of iron.
[0042] The method further includes a step of casting the molten alloy at a predetermined
temperature [shown in block 103], which may range from 900 ºC to 1600 ºC, to produce
the work piece. The casting may be performed by way of continuous casting, solid
casting, billet casting, slab casting, mold casting and among others, where such casted
work piece may be retrievable for further processing and producing of the brake drum
(1).
[0043] At block 104, the method further comprises subjecting the work piece to one or
more heat treatment processes such as but not limited to, annealing, cooling (including
rapid cooling or regulated cooling), quenching (including air quenching, or oil quenching,
or water quenching), hot rolling, cold rolling, and among others. In the illustrative
embodiment, the work piece is subjected to slow cooling or regulated cooling in order to
produce microstructure including substantially of pearlite, and combined proportion of
ferrites and steadies not exceeding 6% of surface area fraction by vol%. Here, the term
13
“substantially” may refer to proportion of the pearlite being 90% or more, while such
proportion may extend upto 94% to 96% of the microstructure. Additionally, the
microstructure so produced may also include graphite flake size in a range of 3-4 microns
and is predominantly A type structure (i.e., pertaining to the graphite flakes). In addition,
due to inclusion of the alloying elements such as Mo, there may be possibility of inclusion
of carbides within the microstructure, where such proportion of carbide may be limited
to 2% or less. Such carbides may impart properties such as strength and/or hardness to
the brake drum (1) so produced.
[0044] In an embodiment, configuration of the work piece after subjecting to one or more
heat treatment processes may include properties such as Brinell hardness at a braking
surface to be ranging from 150 to 200 BHN, generate and maintain frequency coefficient
of damping ranging from 210 to 360 N s/m, on engagement under friction.
[0045] Referring to block 105, the method comprises a step of forming the drum brake
by machining the work piece being subjected to one or more heat treatment processes. In
the illustrative embodiment, the forming process may be including, rolling, cutting,
turning, facing, reaming, boring, tapping, grinding, polishing, and among other processes.
Here, the sequence of forming process should not be construed as a limitation, as
intermediate processes may be suitably performed at required stages for producing the
brake drum (1). Also, processes from the sequence may be omitted as required for
producing the brake drum (1). In an embodiment, the forming process may be performed
at room temperature or may be performed by re-heating the work piece to a temperature
ranging from 450℃ to 1100℃.
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[0046] The following portions of the present disclosure provide details about the
proportion of each alloying element in a composition of the steel and their role in
enhancing properties.
[0047] Carbon (C) may be used in the range between 3 wt% to 3.3 wt%. carbon is present
in the form of graphite and results in a softer iron, more machinable, reduces shrinkage
and reduces density.
[0048] Silicon (Si) may be used minimum in the range of 1.8 wt% to 2.3 wt%. Silicon is
employed to restrict carbide formation and promote development of graphite matrix (i.e.,
graphite flake size) when Si is added about 1.5 wt% or higher. i.e., higher Si contents
tends to increase graphitization potential as well as castability of iron.
[0049] Manganese (Mn) may be used in the range of 0.6 wt% to 0.9 wt%. Mn impacts
properties such as tensile strength and hardenability of the work piece and assists in
controlling adverse effect of sulphur on the mechanical properties.
[0050] Chromium (Cr) may be used in the range 0.1 wt% to 0.33 wt%. Proportion of Cr
is restricted to 0.33 % as the same may form chromium carbides, which are hard particles
and tends to generate high frequency brake squeal noise. Accordingly, proportion of Cr
is restrictive in the present disclosure.
[0051] Copper (Cu) may be added in the range of 0.1 wt% to 0.3 wt%. Cu addition may
impact properties such as hardness and tensile strength of the workpiece.
[0052] Tin (Sn) may be added in range of 0.15% to 0.2 wt%. The addition of Sn tends to
impact properties such as tensile strength of the workpiece and tends to promote
formation of pearlite and/or steadites.
[0053] Molybdenum (Mo) may be added in range of 0.15 wt% to 0.2 wt%. Addition of
Mo may promote refinement of graphite flake size and/or structure, precipitation of small
carbides and increases the hardness.
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[0054] Example:
[0055] Further embodiments of the present disclosure will be now described with
examples of particular compositions of the grey cast iron. Results have been compared
on various fronts to show the effect of various alloying elements in improvement of
strength, wear and corrosion resistance of the grey cast iron. The compositions of the grey
cast iron that are assessed are as shown in below table 1.
COMPOSITION FOR LOW HARDNESS brake drum
(1)
ELEMENT % MINIMUM MAXIMUM
CARBON 3 3.3
SILICON 1.8 2.3
MANGANESE 0.6 0.9
SULPHUR 0.06 0.1
PHOSPHOROUS 0.04 0.1
CHROMIUM 0.1 0.3
TIN / MOLYBDENUM 0.15 0.2
COPPER 0.1 0.3
Table – 1
In an embodiment of the present disclosure, various experiments were carried out on the
formed brake drum (1) considering as a sample with varying composition as mentioned
in table (2) – 1. For conducting the experiment, the sample of pre-determined dimensions
may be prepared by the method of the present disclosure. In an embodiment of the present
disclosure, the hardness testing may involve mounting the specimen in a Brinell Hardness
testing machine and the hardness values at braking surface ranges from 150 to 200 BHN.
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[0056] Referring to figures. 3A – 3B, which are exemplary embodiments of the present
disclosure, illustrating microstructure of the brake drum (1) sample. Figure 3A represents
the microstructure of the brake drum (1) includes substantially of pearlite, and combined
proportion of ferrites and steadites not exceeding 6% of surface area fraction by vol%.
The microstructure can further be seen to include graphite flake size in a range of 3-4
microns and is predominantly A type structure (i.e., pertaining to the graphite flakes).
Also, due to inclusion of the alloying elements such as Mo or Cr, there may be possibility
of inclusion of carbides within the microstructure, where such proportion of carbide may
be limited to 2% or less.
[0057] Moreover, Figure 3 depicts experimental comparison of noise generation on
actuation of the drum brake assembly (10) for engagement of the brake drum (1) and the
brake liner (3) which are prepared in accordance with the present disclosure vis-à-vis
conventional drum brake assembly (10). It can be noted that noise generation has been
substantially reduced and that combination of the brake drum (1) and the brake liner (3)
of the present disclosure negates generation of noise at various frequencies and intervals.
Such examples can be seen in Table 2 below.
Brake Noise Trial
Improved Drum Existing Drum
% No brake noise Event 81.64 20.4
% of brake noise event between 70dB -75dB 4.68 13.8
% of brake noise event between 75 dB -80 dB 4.68 11.5
% of brake noise event between 80 dB -85 dB 8.98 13.4
% of brake noise event between 85 dB -90 dB 0.00 18.4
% of brake noise event between 90 dB -95 dB 0.00 13.0
17
% of brake noise event between 95 dB -100
dB 0.00 7.8
% of brake noise event between 100 dB -105
dB 0.00 1.4
% of brake noise event between 105 dB -110
dB 0.00 0.2
Table 2.
[0058] From the above Table 2, it is to be noted that the existing drum refers to
conventional brake drum, while the improved drum refers to the brake drum (1) produced
in the present disclosed for incorporating in the drum brake assembly (10). The
experiment has been conducted by engaging the brake drum (1) of the present disclosure
with the brake liner (3) of the present disclosure, in comparison with the conventional
brake drum and the brake liner (3) of the present disclosure. Based on such
experimentation and the values deduced thereto, it is to be observed that the combination
of the brake drum (1) and the brake liner (3) of the present disclosure substantially has
minimal to no noise event at higher decibels in which may produce screeching/squealing
noise during operation. Also, it is to be noted that such experimentation has been
performed considering that the coefficient of friction between the brake drum – liner pair
is maintained in a range between 0.35 to 0.45 at a temperature ranging from 50⁰C to
300⁰C.
[0059] In an embodiment of the present disclosure, the drum brake assembly (10) of the
present disclosure may be S-cam brake assembly used any application including but not
limiting to heavy vehicles, light vehicles, passenger vehicles, and the like. Further, such
brake assembly may also be employed in any other industrial applications such as trolley
conveyors, and the like.
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Equivalents:
With respect to the use of substantially any plural and/or singular terms herein, those
having skill in the art can translate from the plural to the singular and/or from the singular
to the plural as is appropriate to the context and/or application. The various singular/plural
permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and
especially in the appended claims (e.g., bodies of the appended claims) are generally
intended as "open" terms (e.g., the term "including" should be interpreted as "including
but not limited to," the term "having" should be interpreted as "having at least," the term
"includes" should be interpreted as "includes but is not limited to," etc.). It will be further
understood by those within the art that if a specific number of an introduced claim
recitation is intended, such an intent will be explicitly recited in the claim, and in the
absence of such recitation no such intent is present. For example, as an aid to
understanding, the following appended claims may contain usage of the introductory
phrases "at least one" and "one or more" to introduce claim recitations. However, the use
of such phrases should not be construed to imply that the introduction of a claim recitation
by the indefinite articles "a" or "an" limits any particular claim containing such introduced
claim recitation to inventions containing only one such recitation, even when the same
claim includes the introductory phrases "one or more" or "at least one" and indefinite
articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean
"at least one" or "one or more"); the same holds true for the use of definite articles used
to introduce claim recitations. In addition, even if a specific number of an introduced
claim recitation is explicitly recited, those skilled in the art will recognize that such
recitation should typically be interpreted to mean at least the recited number (e.g., the
bare recitation of "two recitations," without other modifiers, typically means at least two
recitations, or two or more recitations). Furthermore, in those instances where a
convention analogous to "at least one of A, B, and C, etc." is used, in general such a
construction is intended in the sense one having skill in the art would understand the
convention (e.g., "a system having at least one of A, B, and C" would include but not be
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limited to systems that have A alone, B alone, C alone, A and B together, A and C
together, B and C together, and/or A, B, and C together, etc.). In those instances where a
convention analogous to "at least one of A, B, or C, etc." is used, in general such a
construction is intended in the sense one having skill in the art would understand the
convention (e.g., "a system having at least one of A, B, or C" would include but not be
limited to systems that have A alone, B alone, C alone, A and B together, A and C
together, B and C together, and/or A, B, and C together, etc.). It will be further understood
by those within the art that virtually any disjunctive word and/or phrase presenting two
or more alternative terms, whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the terms, either of the
terms, or both terms. For example, the phrase "A or B" will be understood to include the
possibilities of "A" or "B" or "A and B."
While various aspects and embodiments have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The various aspects and
embodiments disclosed herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the following claims.
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We claim:
1. A drum brake assembly (10) of a vehicle, the drum brake assembly (10) comprising:
a brake drum (1) connectable to an axle of the vehicle, the brake drum (1) being
made from a ferrous based material defined with composition (in wt.%)
comprising:
C in a range of 3% to 3.3%;
Si in a range of 1.8% to 2.3%;
Mn in a range of 0.6%% to 0.9%;
S in a range of 0.06% to 0.1%;
P in a range of 0.04% to 0.1%;
Cr in a range of 0.1% to 0.33%;
Cu in a range of 0.1% to 0.3%,
at least one of Sn or Mo in a range of 0.15% to 0.2%, and
reminder of the composition being Fe along with incidental elements;
a brake shoe (2) disposable along an inner periphery of the brake drum (1); and
a brake liner (3) disposable between the brake shoe (2) and the inner periphery of
the brake drum (1), the brake liner (3) being made from a second material, wherein
the brake liner (3) configured to engage with the brake drum (1) by generating
and maintaining a coefficient of friction ranging between 0.35 to 0.45 at a
temperature ranging from 50⁰C to 300⁰C.
2. The brake assembly as claimed in claim 1, wherein the second material of the brake
liner (3) includes carbon surface area in a range of 1.2% to 1.4%.
3. The brake assembly as claimed in claim 1, wherein the brake liner (3) is configured
to maintain cold compressibility between 60micro to 100micro, on engagement with
the brake drum (1), at a pressure ranging from 0.2 bar to 12bar, to generate and
maintain the coefficient of friction ranging between 0.35 to 0.45.
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4. The brake assembly as claimed in claim 1, wherein the brake drum (1) defined with a
microstructure including substantially of pearlite, and combined proportion of ferrites
and steadites not exceeding 6% of surface area fraction by vol%.
5. The brake assembly as claimed in claim 4, wherein the microstructure of the brake
drum (1) includes a graphite flake size in a range of 3-4 microns and is predominantly
A type structure.
6. The brake assembly as claimed in claim 4, wherein the brake drum (1) being defined
with Brinell hardness at a braking surface to be ranging from 150 to 200 BHN.
7. The brake assembly as claimed in claim 1, wherein the brake liner (3) and the brake
drum (1) configured to generate and maintain frequency coefficient of damping
ranging from 210 to 360 N s/m, on engagement under friction.
8. The brake assembly as claimed in claim 1, wherein the brake shoe (2) being made
from a cast iron material, and wherein the brake liner (3) is operatively flush and fixed
along an outer peripheral surface of the brake shoe (2).
9. The brake assembly as claimed in claim 1, wherein the brake liner (3) includes
porosity in a range of 1.80% to 2.4% and a Rockwell hardness ranging between 46 to
61 (in M Scale).
10. The brake assembly as claimed in claim 1, wherein the brake shoe (2) is made from
cast iron of SG 550/6 grade.