FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION An improved brake booster 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. Deepak R R, Mr. Anshuman Gupta, Mr.Bisen Badal, 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 describes the invention and the manner in which it is performed.

FIELD OF INVENTION:
This invention relates to a brake system of an automobile and more particularly it relates to hydraulic brake system with vacuum booster.
BACKGROUND OF INVENTION:
All automobiles are provided with brake system to reduce risk of any mishap. Hydraulic brake system is one of the commonly used brake systems in cars, Utility vehicles(UV) and Light Commercial Vehicle (LCV)s. Conventional Hydraulic brake circuit (as shown in figure 1) mainly consist of a brake pedal (1), vacuum booster (5), tandem master cylinder, fluid reservoir, disc/ drum brakes & bundy tubes (not shown). The brake booster (5) is having two chambers (6a, 6b) separated by a diaphragm (6) and fluidly communicating through a valve body (15). The valve body is configured to connect and disconnect the fluidic communication between two chambers on release and applied condition of the brake respectively. The force applied by the driver at the pedal end (1) is transmitted by push rod (3) connected though clevis pin(2) when the pedal is pressed the movement of the pedal(l) causes the movement of valve body (15) which in turn directs the air into the 6 a side of the vacuum booster (5) because of the difference in pressure on either side (6a,6b) of diaphragm (6) the input force at brake pedal (1) gets amplified in the vacuum booster (5) and this is transmitted to the disc/ drum to stop the vehicle( well known to the people iin the state of art). Many vehicles have been reported with poor brake feel due to poor co-relation/ relationship between the pedal effort applied, pedal travel, deceleration level achieved and stopping distance. Brake feel also depend upon the time lag between the force applied on brake pedal and the response of braking system. Hence "brake feel" can be improved by reducing the response time of the brake system.
Apart from modifications/ analysis done on disc/ drum brakes, brake pedal etc, the analysis of the brake booster has always being done considering the vacuum pump side of the diaphragm (6b) with modifications being suggested for the same like increasing the vacuum pump size or adding a vacuum reservoir.
WO9605091 teaches pneumatic brake booster for motor vehicle which is able to dispense with a pressure reservoir for a brake booster that works with pneumatic overpressure and is actuated by means of a brake pedal, which consists of first chamber on the brake pedal side of a movable wall which divides the booster housing into two chambers having a continuous

connection with a compressed-air source and that when actuated, a control valve controlling the pneumatic pressure differential acting on the movable wall establishing a connection to the atmosphere for the second chamber on the side of the movable wall facing away from the brake pedal.
The drawbacks associated with above said prior art is that in this case specially designed booster is required and it cannot be easily accommodated on tlie existing normal boosters.
OBJECTS OF THE INVENTION:
> The main object of this invention is to provide a brake system having improved response time to enhance the "brake feel" of the automobile.
> Another object of this invention is to provide a brake system with an increased knee point position so as to increase the range of operation of booster and tandem master cylinder.
> Yet another object of this invention is to provide a brake system which is simple in construction and cost effective.
SUMMARY OF INVENTION:
The present invention discloses an improved brake booster for automobiles comprising;
two fluidly communicating chambers with at least one resilient separator to maintain and control difference of air pressure in said chambers;
a valve body assembly for connecting and disconnecting the fluid communication between said chambers on release and applied condition of the brake respectively;
a brake pedal (1) connected to a rod (3) having resilient means is fitted at one end of said valve body assembly (15);
at least one air suction device adapted for generating vacuum in the chambers of said brake booster assembly (5);
at least one air compressing device connected to one of the chambers through the valve body
assembly of said brake booster assembly (5) for providing pressurized air during brake application; and at least one alternate arrangement provided on integrated boost reservoir (4) for effective working of said brake booster on atmospheric air.

The brake booster as claimed in claim 1 wherein said booster having at least one integrated boost reservoir (4) connected to said compressed air source and adapted for storing and providing compressed air to said valve body assembly (15).
The air compressing devices are turbocharger of a vehicle or a separate compressor unit or any similar devices. Integrated boost reservoir (4) is connected to compressed air source (17) through air inlet passage (8) vide hose (18). Compressed air is provided to vacuum booster (5) through passage (13) connected to outlet port (12) of integrated boost reservoir (4) and inlet port (140 of said valve body (15).
Push rod (3) actuates the valves (19) and (20) present in the valve body assembly (5) allowing air to move axially inside said booster. The separator with resilient means is diaphragm (6) which separates the two chambers (6a, 6b) inside the vacuum booster (5).
The integrated boost reservoir (4) is provided with at least one outlet port (12) for providing compressed air to said valve body assembly (15) through inlet port (14).
The alternate arrangement provided at the integrated boost reservoir (4) is a fail-safe arrangement comprising of a pressure isolator (11) operating on differential pressure between atmosphere & compressed air across filter (10) having cap (9) to allow atmospheric air to fill integrated boost reservoir with air at atmospheric pressure during faulty operation of said air compressing devices.
When brakes are not applied said air suction device generates vacuum by continuous evacuation through (NRV) non-return valve (7) for maintaining equal level of vacuum on both sides (6a, 6b) of the diaphragm (6).
STATEMENT OF INVENTION:
Accordingly the present invention provides an improved brake booster for automobiles
comprising;
two fluidly communicating chambers with at least one resilient separator to maintain and
control difference of air pressure in said chambers;

a valve body assembly for connecting and disconnecting the fluid communication between
said chambers on release and applied condition of the brake respectively;
a brake pedal (1) connected to a rod (3) having resilient means is fitted at one end of said
valve body assembly (15);
at least one air suction device adapted for generating vacuum in the chambers of said brake
booster assembly (5);
at least one air compressing device connected to one of the chambers through the valve body
assembly of said brake booster assembly (5) for providing pressurized air during brake
application; and
at least one alternate arrangement provided on integrated boost reservoir (4) for effective
working of said brake booster on atmospheric air.
BRIEF DESCRIPTION OF INVENTION:
Improved brake system for automobile in accordance with this invention comprises of a compressed air source, brake booster, a reservoir integrated with brake booster and brake pedal assembly. The said compressed air source and the integrated boost reservoir are pneumatically connected. The said brake pedal assembly is mechanically connected to the brake booster.
The brake booster gets actuated through a mechanical linkages and the integrated boost reservoir, which is pneumatically connected to compressed air source, directs the compressed air into the brake booster.
The differential pressure in the brake booster has increased because of compressed air fed to it instead of air at atmospheric pressure which enhances the braking assistance.
In case of any failure/ leakage in pressurized air circuit, integrated boost reservoir shall set system to open to atmospheric pressure wherein it would act as a normal brake booster.
This invention finally aims at reducing the response time of the brake circuit and thereby reducing the stopping distance and improving the "brake feel" of an automobile.
BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 shows a conventional booster for reference
Figure 2 shows the layout of brake system in accordance with the invention
Figure 3 shows the brake booster in released condition
Figure 4shows the brake booster in applied condition.
Figure 5 shows comparison between conventional & modified vacuum booster with TMC in
relation to TMC pressure generation with time.
Figure 6 shows comparison between conventional & modified vacuum booster with TMC in
relation to automobile stopping distance with time for same pedal effort.
DETAILED DESCRIPTION OF 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,
Referring to figures 2, 3 and 4 improved brake system comprises of a brake pedal (1) and a clevis pin (2) connecting brake pedal (1) with booster pushrod (3) fitted at the end of valve body assembly (15) of vacuum booster (5). An integrated boost reservoir (4) is a part of vacuum booster (5) outer body which is connected to the compressed air source (17) through an air passage (8) via hose (18). Vacuum booster's (5) valve body (15) receives compressed air through passage (13) connected to the outlet port (12) of integrated boost reservoir (4), inlet port (14) of valve body (15)). A fail-safe arrangement is provided on integrated boost reservoir (4) in case of any malfunctioning in compressed air source.
Brake pedal (1) transfers motion to vacuum booster (5) through a clevis pin (2) via push rod (3). Said push rod (3) actuates the valves (19) and (20) present in the valve body assembly (5) thereby allowing air to move axially inside the booster. The vacuum booster (5) in vehicles is used to give the required assist or boost during braking. It works on the principle of differential pressure. A diaphragm (6) separates the two chambers (6a, 6b) inside the vacuum booster (5). When no brakes are applied, continuous evacuation is done by engine suction means or by vacuum pump installed on engine through NRV non-return valve (7) maintaining equal level of vacuum on both sides (6a, 6b) of the diaphragm (6). Integrated boost reservoir (4) is a chamber where compressed air is directed through a passage (8) which communicates to a pressure source (16 & 17)via hose (18). An outlet port

(12) of integrated boost reservoir (4) is connected to the valve body's inlet port (14) via passage (13).
A fail-safe arrangement is provided at the integrated boost reservoir (4) which would work during faulty operation of compressed air source. Pressure isolator (11) operates on differential pressure between atmosphere & compressed air across filter (10) having cap (9). Hence, it will allow atmospheric air to fill integrated boost reservoir with air at atmospheric pressure. This would render back conventional function of booster.
The compressed air source which here is turbocharger (16) of the vehicle compresses the atmospheric air to a relatively high value which then enters the intercooler (17) where the temperature of the compressed hot air is brought down. In this invention, some amount of air coming out of the intercooler (17) is bled and sent to the integrated boost reservoir (4). A . separate compressor or any other source of compressed air can also be used for supplying the compressed air.
Normally when the brake is not applied, the valve body (15) remains in closed condition and prevents entry of compressed air from integrated boost reservoir (4). When the brake pedal (1) is advancing for brake application it experience a greater load on the push rod (3) and the push-rod (3) opens the valve (19) for entry of pressurized air in one side (6a) of diaphragm (6) and simultaneously closes valve (20) for closing/shutting passage of vacuum to said side (6a) of diaphragm (6) in valve assembly (15), allowing compressed air from integrated boost reservoir (4), via passage (13), to enter the vacuum booster (5) on one side of the diaphragm (6a) along with parallely sealing off the vacuum to that side (shown by both lines & arrows). This increases pressure on diaphragm (6) thereby amplifying the force available. The compressed air entering through the valve assembly (15) flows radially outwards inside the booster chamber in a uniform fashion leading to equal pressure application on the diaphragm (6) area. Due to compressed high pressure air on one side (6a) of diaphragm (6) and vacuum on other side (6b), high differential pressure is created and hence push rod (3) operates faster as compared to the earlier system of using air at atmospheric pressure at the pushrod side of vacuum booster (5). This higher differential pressure will lead to obtaining better brake booster characteristics in terms of response time as well as improved brake feel.

As the brake pedal (1) is released, the valve returns to its original position and prevents entry of outside air supply by closing the valve (19) in one side (6a) of diaphragm (6) and simultaneously opening valve (20) for connecting passage of vacuum to said side (6a) of diaphragm (6) in valve assembly (15). This restores vacuum to both sides (6a, 6b) of the diaphragm (6) during this time integrated boost reservoir (4) continue to receive compressed air till its capacity & becomes ready for next brake application.
In the absence of the air pressure, due to fault in compressed air source, in the integrated boost reservoir (4) pressure isolator (11) will pneumatically get open to atmosphere thereby allowing atmospheric air through air filter (10) to fill the space which would be used while brake application, thereby safeguarding the system by allowing vacuum booster (7) to work normally as conventional one..
The differentiation in performance is shown between the Conventional system and the Present Invention:
Fig. 5 shows a graph showing position of knee point and reaction time by this system ascompared to conventional system The graph compares conventional & modified vacuum booster with TMC in relation to hydraulic pressure generation with time. Clearly there has been marked reduction in the response time of the brake system. This reduction of response time leads to "improved brake feel".
Further, there has been increase in knee point and maximum pressure generation with the modified vacuum booster with TMC leading to increase in the working range of TMC.
Fig, 6 shows a graph showing stopping distance of automobile with this system as compared to conventional system for same pedal efforts
The graph compares conventional & modified vacuum booster with TMC in relation to automobile stopping distance with time. Clearly there has been marked reduction in automobile stopping distance under same testing conditions. Since automobile stopping distance is related to the deceleration level achieved hence, driver will get a feedback of more deceleration level generation for same pedal efforts and would perceive improvement in "brake feel"

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 improved brake booster for automobiles comprising;
two fluidly communicating chambers with at least one resilient separator to maintain and control difference of air pressure in said chambers;
a valve body assembly for connecting and disconnecting the fluid communication between said chambers on release and applied condition of the brake respectively;
a brake pedal (1) connected to a rod (3) having resilient means is fitted at one end of said valve body assembly (15);
at least one air suction device adapted for generating vacuum in the chambers of said brake booster assembly (5);
at least one air compressing device connected to one of the chambers through the valve body assembly of said brake booster assembly (5) for providing pressurized air during brake application; and
at least one alternate arrangement provided on integrated boost reservoir (4) for effective working of said brake booster on atmospheric air.
2. The brake booster as claimed in claim 1 wherein said booster having at least one integrated boost reservoir (4) connected to said compressed air source and adapted for storing and providing compressed air to said valve body assembly (15).
3. The brake booster as claimed in claim 1 wherein said air compressing devices are turbo charger of a vehicle or a separate compressor unit or any similar devices.
4. The brake booster as claimed in claim 1 wherein said integrated boost reservoir (4) is connected to compressed air source (17) through air inlet passage (8) vide hose (18).
5. The brake booster as claimed in claim 1 wherein said compressed air is provided to vacuum booster (5) through passage (13) connected to outlet port (12) of integrated boost reservoir (4) and inlet port (14) of said valve body (15).
6. The brake booster as claimed in claim 1 wherein said push rod (3) actuates the valves (19) and (20) present in the valve body assembly (5) allowing air to move axially inside said booster.

7. The brake booster as claimed in claim 1 wherein said separator with resilient means is diaphragm (6) which separates the two chambers (6a, 6b) inside the vacuum booster (5).
8. The brake booster as claimed in claim 1 wherein said alternate arrangement provided at the integrated boost reservoir (4) is a fail-safe arrangement comprising of a pressure isolator (11) operating on differential pressure between atmosphere & compressed air across filter (10) having cap (9) to allow atmospheric air to fill integrated boost reservoir with air at atmospheric pressure during faulty operation of said air compressing devices.
9. The brake booster as claimed in claim 1 wherein when brakes are not applied said air suction device generates vacuum by continuous evacuation through (NRV) non-return valve (7) for maintaining equal level of vacuum on both sides (6a, 6b) of the diaphragm (6).
10. The improved brake booster for automobiles substantially as herein described with reference to accompanying drawings.