FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Partial Ribbed Hub cum Brake Drum with at least 3 Bolts Mounting


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Parag Phirke, Tushar Patil, Umesh Abhayankar
Shrinivas Sharangpani and Bisen Badal
all Indian national of TATA MOTORS LIMITED,
an Indian company having its registered office at
Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE OF THE DESCRIPTION
The following specification describes the invention


Field of Invention:
This invention relates to the hub cum brake drum and more particularly to the Brake drum used in brake drum assembly in which drum is weight and cost effective with all desirable characteristics of brake drum during braking.
Background of the Invention:
Generally conventional type of brake drums (fig-l) are made of casting and ribs of same and other material added on its outer surfaces for achieving cooling, strength and noise reduction generated during braking such brake drums are quite bulky in nature and costlier from manufacturing point of vie\y. Braking system for vehicles with a hub cum Brake Drum which is mounted over four or six bolts increases the cost and weight of the system. Braking system for vehicles with conventional Brake Drum is heavy, fow in strength, high in cost and makes the machining of the component difficult and time consuming as with machining surface of brake drum incapable of holding properly between the jaws of Machine for precise machining operations. The casting of the product usually makes non-uniform weight distribution and causes imbalance. Again braking system for vehicles with a Brake Drum is inefficient in Noise Reduction generated during Braking. Braking system for vehicles with existing Brake Drum is incapable for dissipating Heat Efficiently Generated during Braking.
Objects of this Invention:
> The Primary objective of this invention is to provide Braking system for vehicles with a hub cum Brake Drum (fig-2) which is mounted over three bolts (IB).
> The other objective of this invention is to provide Braking system for vehicles with a Partial Ribs (1C) on outer periphery of Brake Drum (fig-2) which is light in weight & less in cost.
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> Yet another objective of this invention is provided with machining surface (ID) of brake drum (fig-2) capable of holding properly between the jaws of Machine for precise machining operations.
> Yet another objective of this invention is to provide Braking system for vehicles with a Brake Drum (fig-2) having good strength because of Partial Ribbed type Structure.
> Yet another objective of this invention is to provide Braking system for vehicles with a Brake Drum (fig-2) Efficient in Noise Reduction generated during Braking.
> Yet another objective of this invention is to provide Braking system for vehicles with Brake drum (fig-2) saving Machining Operations, cost & time.
> Yet another objective of this invention is to provide Braking system for vehicles with Brake Drum (fig-2) Capable for dissipating Heat Efficiently Generated during Braking.
Statement of the Invention:
Partial Ribbed Hub cum Brake Drum with at least 3 bolts mounting comprising:
- a hub cum brake drum with the partial ribs on its outer periphery,
- a machining surface on said outer periphery for holding during machining operations,
- at least three mounting holes arrangement to assemble on vehicle.
Brake drum is suitable due to its light weight for all types of vehicle which are basically designed with reduced weight for taking the advantage of fuel economy. Brake drum of this invention is made light weight and low cost by providing a Partial rib (reduce material) on its outer periphery. Brake drum is efficient in heat dissipation as ribs type structure on its periphery increase the surface area of contact with respect to atmospheric air, hence transferring heat efficiently without adding any additional
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material having good heat dissipation characteristics. Brake drum is robust and has good strength because of its ribbed type structure on its outer periphery and is capable of reducing noise generated during braking due to its compact design.
Brief description of Drawings:
FIG.l shows isometric view of the conventional type of Hub cum Brake Drum of
Braking system for vehicles having in accordance with this invention.
FIG.2 shows isometric view of Hub cum Brake Drum with Partial Ribs on its outer
surface of Braking system for vehicles having in accordance with this invention.
FIG.3 shows cross sectional view of conventional hub Brake Drum of Braking system
for vehicles having in accordance with this invention.
FIG.4 shows cross sectional view over partial rib of hub cum Brake Drum of Braking
system for vehicles having in accordance with this invention.
FIG.5 shows cross sectional view of partial ribbed type Brake Drum of Braking
system for vehicles having in accordance with this invention.
FIG.6 shows Right view of partial ribbed type hub cum Brake Drum of Braking
system for vehicles having in accordance with this invention.
FIG.7 shows Front view of partial ribbed type hub cum brake Drum of Braking
system for vehicle having in accordance with this invention.
Detailed description of the Invention:
Now new generation vehicles are designed light in weight to gain maximum advantage of fuel economy. Therefore Brake drum of this invention (fig-2) has all the desirable characteristics over conventional brake drum (fig-1) with light weight, less cost and less imbalance values. Brake drum of this invention differs from conventional brake drum (fig-1) in the sense that it is hub cum brake drum assembled with three bolts Mounting and made up of partial ribs (1C) on its overall outer periphery which added some special characteristics to the drum and also provided
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with machining surface (ID) for holding brake drum in jaws for further machining operation carried out for maintaining proper runout and less imbalance value. Such structure is compact in nature which adds strength to the drum and increases the outer surface area of the brake drum thereby reducing the weight and cost of material and machining to some extent.
In the design of new generation vehicles weight of vehicle play an important role to achieve fuel economy. Fuel economy improvements demand size and weight reduction of motor vehicle components while often at the same time requiring improvement structural properties. Fuel economy increase with reduced vehicle weight. Hence this invention relates in general to vehicle brake drum Assembly and more particularly to an improved structure for a brake drum (fig-2) which is light in weight and reduce in cost for use in such a vehicle brake drum assembly.
With modern road speeds becoming higher and necessitating braking of vehicle from high speed Vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system includes either a disc brake assembly or a drum brake assembly for each of the wheels. The brake assemblies are typically actuated by hydraulic or pneumatic pressure generated by an operator of the vehicle depressing a foot pedal, pulling a hand lever, and the like. The drum brake assembly includes a backing plate which is secured to a fixed, non-rotatable component of the vehicle, such as the vehicle axle housing (not shown). A pair of opposed accurate brake shoes (Two brake shoe is illustrated), are supported on the backing plate for selective movement relative thereto. Each of the brake shoes have a friction pad secured thereto. The brake drum assembly further includes a hollow cylindrical brake drum (fig-1) which is secured to a vehicle wheel (not shown) for rotation therewith. The hollow interior of the brake drum defines an inner cylindrical braking surface (1A). The brake drum is disposed adjacent to the backing
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plate such that the brake shoes extend within the cylindrical braking surface (1A). To effect braking action, the brake shoes are moved outwardly apart from one another such that the friction pads frictionally engage the cylindrical braking surface (1A) of the brake drum. Such frictional engagement causes slowing or stopping of the rotational movement of the brake drum and, therefore, the wheel of the vehicle in a controlled manner. As discussed above, the rotating inner cylindrical braking surface (1A) of the brake drum (fig-1) is frictionally engaged by the non-rotating friction pads of the brake shoes during braking. As a result, brake noise is commonly generated during braking. One source of brake noise can be generated by the brake drum (fig-1) resonating at its natural frequency. Typically, the natural frequency of the brake drum (fig-1) is in the range of 2000 Hz to 5000 Hz but can increase to near 15,000 Hz, and the magnitude of the brake noise generated during braking is in the range of 80 dBa to 120 dBa but can be in excess of 120 dBa. Reasons for producing braking noise are mainly due to improper runout and uneven machining over brake drum which may also causes unbalance of wheel.
Drum brakes (fig-1) are also designed to convert kinetic energy into heat energy via the process of Friction. This heat is intended to be further transferred to atmosphere, but can just as easily transfer into other components of the braking system. Brake drums (fig-1) have to be substantial pieces of Steel or Cast Iron to cope with the forces that are involved which can retain a lot of heat. Heat transfer to atmosphere can be aided by incorporating fins/ribs (fig-2) into the design of the drum. However, excessive heating can occur due to heavy or repeated braking which can cause the drum to distort, leading to vibration under braking. When the drums (fig-1) are heated by hard braking, the diameter of the drum increases slightly due to Thermal Expansion of the material, this means the brakes shoes have to move further and the brake pedal has to be depressed more. The properties of the friction material can change if heated, creating less friction. Excessive heating of the brake drums can
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cause the Brake Fluid to Vaporize, which reduces the Hydraulic Pressure being applied to the brake shoes.
Hence by considering the above factors which illustrate the disadvantages during braking brake drum of this invention (Fig-2) is so design which is weight and cost effective and also capable of having efficient heat dissipation and noise reduction characteristic with sufficient strength and Proper Balancing of brake drum & wheel.
This invention basically relates to an improved structure for a hub cum brake drum (fig-2) adapted for use in a drum brake assembly which is effective from weight and cost point of view with proper balancing when mounted over three bolts (IB) on vehicle. This can be achieved by Providing a Partial ribs (IC) on overall outer periphery of the drum and also provided machining surface (IC) for proper holding between jaws during various machining operations performed over drum. It is also provided with three mounting holes (IB) which hold the brake drum assembly in well balanced condition hence reducing the effect of unbalance of wheel. Proper Balancing and maintaining runout are the most desirable factors that to be considered in the design of brake drum. These factors can only be achieved when drum machined precisely for that drum need to be hold properly between the jaws or on fixtures during machining operation. As a result of Partial ribs (IC) on outer surface of the drum, gains some additional advantages such as compensate the effect of heat and noise generation during braking. Brake drum of this invention is light in weight and less in cost to some extent which contribute to reduce the weight and cost of vehicle as there are four number of brake drum are mounted on each vehicle. Brake drum of this invention is manufacture in casting and not required any machining operation on the overall outer surface hence saving time and cost over machining operations. Due to Partial rib type structure, area of the outer surface increases therefore more the area is in contact with the atmospheric air, more will be the heat dissipation. Hence this
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structure also Contribute to heat Dissipation characteristic of the brake drum. Ribs on the outer surface make the brake drum design more Robust & compact in nature due to which strength of the brake drum increase. Ribbed type structure of the brake drum also contribute to minimize the brake drum from resonating at its natural frequency by changing the excitation frequency of the brake drum thereby reducing the brake noise generated by the drum during braking . Braking system for vehicles accordance with this invention basically comprises of Brake drum assembly having Brake shoe, Auto adjuster, Brake Linings, Wheel Cylinder Assembly, Back Plate, Drum (fig-2) etc.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.
Dated this 19th day of March 2009
TATA MOTORS LIMITED By their Agent & Attorney

(Karuna Goleria) of De PENNING & De PENNING
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