FORM 2


THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Integrated service and parking brake system for automobiles
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
Mr. G. R. Nagbhushan, Mr. Badal G Bisen , Mr. Anshuman Gupta
all Indian nationals 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 TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.

FIELD OF INVENTION
This invention relates to automobile brake system and more particularly it relates to an integrated parking and service brake system for automobiles.
BACKGROUND OF THE INVENTION
All automobiles are provided with brake system to decelerate, stop and hold the vehicle as desired by the driver and to reduce risk of any mishap. Brake system generally comprises of service brakes and emergency or parking brakes. Generally hydraulic brakes are used as a service brakes which consist of hydraulic circuit with brake fluid and emergency/ parking brake system generally are mechanically applied type.
Hydraulic brake circuit mainly consist of a brake pedal, vacuum booster, tandem master cylinder, fluid reservoir, disc/ drum brakes and bundy tubes such as metal tubes, whereas emergency/ parking brake system mainly consist of parking brake lever, parking brake cables and equalizer.
The sole purpose of using different brake systems is to have a failsafe option in case of failure in one system. Use of two separate brake system in a vehicle requires separate brake system design and leads extra cost.
US 6405837 describes a braking device having a service brake and a parking brake. The braking device includes a housing and a shaft that extends at least partially through the housing. The shaft is rotatable relative to the housing about a longitudinal axis. A stack of plates is spaced axially along the shaft. At least one of the plates is adapted to rotate in concert with the shaft. The stack of plates includes a first axial
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end positioned opposite from a second axial end. A spring structure is provided for compressing the stack of plates together to provide the parking brake. The spring structure is mounted at the first axial end of the stack of plates. The braking device also includes a first piston for releasing the parking brake, and a second piston for actuating the service brake. The second piston actuates the service brake. The second piston is mounted at the second axial end of the stack of plates. When actuated, the second piston forces the plates axially toward the spring assembly such that the plates are compressed together to provide the service brake.
The drawbacks associated with above said prior art is that in this case specially designed foundation brake is required and it cannot be easily accommodated on the existing brake circuit.
OBJECTS OF INVENTION
> Main objective of this invention is to provide an integrated service and parking brake system with desired brake performance.
> Yet another object of this invention is to provide an integrated service and parking brake system with two separate operating means for service and parking brake application.
> Yet another object of this invention is to provide an integrated service and parking brake system which is simple in construction and cost effective.
STATEMENT OF INVENTION
An integrated service and parking brake system for automobiles comprising:

a service brake input means being hydraulically connected to front brake unit and to rear brake actuation unit;
a parking brake input means being mechanically connected to said rear brake actuation unit;
said rear brake actuation unit further comprising:
a sliding piston with an integrated pushrod, said sliding piston configured to divide said actuation unit into a hydraulic fluid chamber and a resilient means chamber;
said service brake input means being connected to said hydraulic fluid chamber;
said parking brake input means being connected to one end of said pushrod;
said resilient means chamber comprises a resilient means provided axially over said pushrod, one end of said resilient means being connected to said sliding piston and other end being connected to a side wall of said actuation unit.
BRIEF DESCRIPTION OF DRAWING
In accordance to the present invention Fig 1 shows a schematic diagram of the brake circuit of integrated service & parking brake system.
BRIEF DESCRIPTION OF INVENTION
In accordance with this invention, integrated service and parking brake system for an automobile comprises; of a servo unit, plurality of foundation brake units, actuation unit such as - hydro-mechanical actuator, service brake input means such as brake

pedal, bundy tubes, parking brake input means such as parking brake lever, parking brake cables and equalizer. Wherein said servo unit comprises of vacuum booster, tandem master cylinder and brake fluid reservoir. Said servo unit is hydraulically connected to front foundation brake units and to the said hydro-mechanical actuator. Wherein Said hydro-mechanical actuator comprises of a sliding piston with integrated pushrod, resilient means like preloaded spring, sealing rings, bearing, feed port and bleeding port. Wherein said sliding piston divides the actuator in to two chambers. Said spring is axially provided over said pushrod at one end, one end of said preloaded spring is connected to said sliding piston and other end is connected to actuator wall.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
Fig 1 shows a schematic diagram of the brake circuit of integrated service & parking brake system.
Integrated service and parking brake system for an automobile in accordance with this invention basically comprises of a servo unit (1), plurality of foundation brake units (15, 20), actuation unit such as - hydro-mechanical actuator (3), service brake input means such as brake pedal (2), bundy tubes (16, 21), parking brake input means such as parking brake lever (10), parking brake cables (11, 14) and equalizer (13). Wherein said servo unit (1) comprises of vacuum booster, tandem master cylinder and brake fluid reservoir. Said servo unit (1) is hydraulically connected to front foundation brake units (20) and to the said hydro-mechanical actuator (3).

Said hydro-mechanical actuator (3) comprises of a sliding piston (4) with integrated pushrod (9, 12), resilient means like preloaded spring (7), sealing rings (8), bearing (17), feed port (18) and bleeding port (19). Wherein said sliding piston (4) divides the actuator (3) in to two chambers. Said spring (7) is axially provided over said pushrod (9, 12) at one end, one end of said preloaded spring (7) is connected to said sliding piston (4) and other end is connected to actuator wall. Said pushrod (9, 12) is extended beyond the actuator at both ends, one of its end preferably spring end (9) is connected to the parking brake lever (10) through parking brake cable (11) and said pushrod (9) towards spring end is supported on said bearing (17), other end of said pushrod (12) is connected to rear foundation brake units (15) through equalizer (13) and rear parking brake cables (14). One sealing ring (8) is provided on said piston (4), and other sealing ring (8) is provided rigidly on hydro-mechanical actuator (3) body so as to seal the hydraulic fluid. Said feed port (18) and bleeding port (19) are provided on said actuator (3) body at its fluid chamber (6). Said rear foundation brake unit (15) comprises of a mechanical brake unit. Said hydro-mechanical actuator (3) is tilted by small angle with bleed port side on top to facilitate the bleeding of air inside the hydraulic system.
During service brake application, when brake pedal (2) is pressed, front wheels directly gets the required brake force from the servo unit (1) however in case of rear wheels the hydraulic fluid acts on sliding piston (4) of a said hydro - mechanical actuator (3), due to which the said push rod (9, 12) pulls the rear parking brake cables (14) via equalizer (13), which in-turn actuates the rear foundation brake (15). On the brake release the preloaded spring (7) slides the movable piston (4) to the equilibrium position, which in-turn releases the pulling force on said rear parking brake cables (14).

During parking brake application the parking brake lever (10) is pulled which in turn pulls the said pushrod (9, 12) through front parking brake cable (11) and pulls the equalizer (13) which in turn operates the rear parking brake cables (14) and hence actuates the rear foundation brake (15). During parking brake lever (10) release, the preloaded spring (7) of hydro-mechanical actuator (3) pushes said piston (4) along with push rod (9, 12) to equilibrium position, which in-turn releases the pulling force on said rear parking brake cables (14).
Said sealing rings (8) help in preventing any leakage of hydraulic fluid in all conditions. Spring chamber side pushrod (9) is provided with a bearing (17) which reduce the friction during sliding operation.
Now referring to fig. 1, integrated service & parking brake system basically comprises of a brake pedal (2) with servo unit (1), a hydro-mechanical actuator(3) with a internally movable piston (4) dividing the space into two chambers viz. hydraulic chamber (6) having a feed port (18) and bleed port (19) & spring chamber (5) having a pre-loaded spring (7). first end (9) of Pushrod connects front parking brake cable (11) to the parking brake lever (10). Second end (12) of pushrod connects to an equalizer (13) which operates the rear brake assembly (15) through rear parking brake cables (14).
Hydraulic application
When the brake pedal (2) is pressed, servo unit (1) amplifies the hydraulic pressure inside the hydraulic circuit actuating the brakes mounted on the individual wheels. Front wheel brakes (20) directly get the actuation pressure through front hydraulic circuit (16) but in case of rear wheels, the hydraulic fluid flowing through rear

hydraulic circuit (21) enters through feed port (18) of hydro-mechanical actuator(3) & pressure acts on the internally movable piston (4) i.e. hydraulic pressure acts on chambers (6) inside the hydro-mechanical actuator(3). Due to this, spring force acting on the spring chamber (5) is overcome by the increasing hydraulic pressure in the hydraulic chamber (6) and hence the movable piston (4) slides in forward direction till the equilibrium point is reached. Second end of Pushrod (12) attached to the piston also slides by the same magnitude, said pushrod (12) protruding out from the hydro-mechanical actuator(3) and pulls the equalizer (13) which in turn pulls the rear parking brake cables (14) actuating the rear brakes (15).
When the force on the brake pedal is released, the hydraulic fluid dumps out and the spring force of the preloaded spring slides (7) the internally movable piston (4) to the equilibrium condition releasing the pulling force acting on the rear parking brake cables (14) and hence the brake force at rear wheels is released.
A bleed port (19) is provided in the hydraulic chamber (6) at the topmost surface of the hydro-mechanical actuator(3) to remove any air from the hydraulic circuit.
Mechanical application
When the parking brake is applied by pulling the parking brake lever (10), the motion is transferred by the front parking brake cable (11) to the first end of pushrod (9) of the hydro-mechanical actuator(3) which in turn pulls the internally movable piston (4) in forward direction against the preloaded spring (7) which is seated between the wall of hydro-mechanical actuator(3) and the movable piston (4) by the help of grooves cut onto them. Due to this forward motion of the movable piston (3), the

pushrod connected to the equalizer also slides by the same magnitude, pulling the rear parking brake cables (14) and thus actuating the rear brakes (15).
When the parking brake is released, the compression force acting on the preloaded spring (7) decreases i.e. the spring expands to the prescribed length, and hence the internally movable piston (4) slides back to the equilibrium position reducing the pulling load on the rear parking brake cables and hence the brake forces on the rear
wheels.
'O'-rings (8) are provided at the sliding surfaces between the hydro-mechanical actuator(3), internally movable piston (4) and the hydraulic chamber (6) side pushrod (12) to restrict any leakage past the hydraulic chamber during all conditions. Bearings (17) are provided to reduce the dry friction level between the first end of said pushrod (9) and said hydro-mechanical actuator(3).
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.

WE CLAIM
1. An integrated service and parking brake system for automobiles comprising:
a service brake input means being hydraulically connected to front brake unit and to rear brake actuation unit;
a parking brake input means being mechanically connected to said rear brake actuation unit;
said rear brake actuation unit further comprising:
a sliding piston with an integrated pushrod, said sliding piston configured to divide said actuation unit into a hydraulic fluid chamber and a resilient means chamber;
said service brake input means being connected to said hydraulic fluid chamber;
said parking brake input means being connected to one end of said pushrod;
said resilient means chamber comprises a resilient means provided axially over said pushrod, one end of said resilient means being connected to said sliding piston and other end being connected to a side wall of said actuation unit.
2. The braking system as claimed in claim 1, wherein said actuation unit is
inclined at predetermined angle for facilitating bleeding of said actuation unit.
3. The braking system as claimed in claim 1, wherein said pushrod is provided to
protrude at both ends of said actuation unit, said parking brake input means is
connected to said protrusion at the resilient means chamber end.
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4. The braking system as claimed in claim 1, wherein said resilient means is a preloaded spring, one end of said spring is connected to a groove in said sliding piston and other end is connected to a groove in side wall of said actuation unit.
5. The braking system as claimed in claim 1, wherein said service brake input means is hydraulically connected to said front brake unit and said rear brake actuation unit through a servo unit.
6. The braking system as claimed in claim 4, wherein hydraulic fluid chamber having a feed port which is actuated through said service brake input means to provide hydraulic pressure inside said fluid chamber.
7. The braking system as claimed in claim 1 or 2, wherein said pushrod at the fluid chamber end of said actuation unit is configured to be connected to rear brakes through an equalizer and brake cables.
8. The braking system as claimed in claim 2, wherein parking brake cables are provided to connect said parking brake input means to said protruding portion of said pushrod.
9. The braking system as claimed in claim 1, wherein said sliding piston and actuation unit are provided with a sealing rings to seal hydraulic fluid leakages.
10. The braking system as claimed in claim 1, wherein said actuation unit having a bleeding port for bleeding air, if any, from said actuation unit.

11. The braking system as claimed in claim 1? wherein bearings are provided to reduce dry friction level between resilient means chamber end of said pushrod and said actuation unit.
12. An integrated service and parking brake1 system for automobiles substantially as hereinabove described with reference to the accompanying drawings.
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Dated this 24th day of February 2009