FORM 2
THE PATENT ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE: "A BRAKE BOOSTER ASSEMBLY FOR VARIABLE BOOST RATIO AND JUMP-IN"
NAME AND ADDRESS OF THE APPLICANT: TATA MOTORS LIMITED, an
Indian company having its registered office at Bombay house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra, INDIA.
Nationality: INDIAN
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Embodiments of the disclosure are related to the brake systems of vehicles and more particular this invention is related to a brake booster assembly.
BACKGROUND OF THE DISCLOSURE AND PRIOR ARTS
The brake booster is designed to create a greater braking force from a minimum pedal effort using difference in atmospheric pressure and vacuum (engine manifold/vacuum pump). It increases the pedal force 2 to 4 times depending on the size of booster. The brake booster is located between brake pedal and master cylinder.
The existing brake booster assembly comprises of valve, plunger and reaction disc, as main components affecting boost ratio and jump-in. The boost ratio is defined as a ratio of square of reaction disc diameter to square of plunger diameter, and the jump-in is defined as gap between the reaction disc and the plunger.
FIGS. 1, 2 and 3 illustrates sectional views of the brake booster device, according to the prior art. The brake booster device comprises a booster body; a booster piston accommodated in the booster body; a diaphragm connected to the booster piston for dividing the booster body into front and rear working chambers, said front working chamber communicating with a vacuum supply source, said rear working chamber selectively communicating with said front working chamber or external atmosphere through a valve body; an input rod located opposite to said booster piston for movement toward and away from said booster piston, said input rod being connected to said valve body to produce a pressure difference between said working chambers for causing said booster piston to follow the forward movement of said input rod; a plunger connected to the input rod is slidably fitted in the front part of a tubular valve casing; a reaction disc mounted inside the valve body and is axially aligned with the plunger.
The principle of the brake booster device is pressure differential. When vacuum is applied to both sides of the booster piston, the piston is pushed by the spring

and remains there. When the atmospheric air is allowed into chamber the piston starts to compress the spring, due to the difference in pressure, and moves to the left. This causes the piston rod to move the piston of the master cylinder, generating hydraulic pressure. The valve mechanism regulates the pressure inside the variable pressure chamber.
One way to modify jump-in force and boost ratio is by providing a change plunger to the plunger using a screw. For example KR20040040069 describes a change plunger attaching to the plunger using a screw.
The common need of any brake booster device irrespective of its size is to have different boost ratios and jump-in. To provide different boost ratios and jump-in, the valve body and the plunger of the existing brake booster device have to be redesigned. Thus a major change needs to be made adding variability of parts. The proposed design in valve body and plunger allows using a common valve body and plunger to achieve different boost ratios and jump-in.
OBJECTS OF THE DISCLOSURE
The object is to provide a brake booster device comprising a common valve body with a variable cover to vary the boost ratio.
Another object is to provide a brake booster device comprising a common plunger with a variable cover to vary the boost ratio and jump-in.
Yet another object of the invention is to provide a brake booster device comprising a common valve body and a plunger with variable cover to vary the boost ratio and jump-in.
Yet another object of the invention is to vary boost ratio and jump-in by varying respective cover thicknesses.
STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure relates to a brake booster device comprising a booster body; a booster piston accommodated in the booster

body; a diaphragm connected to the booster piston for dividing the booster body into front and rear working chambers, said front working chamber communicating with a vacuum supply source, said rear working chamber selectively communicating with said front working chamber or external atmosphere through a valve body; an input rod located opposite to said booster piston for movement toward and away from said booster piston, said input rod being connected to said valve body to produce a pressure difference between said working chambers for causing said booster piston to follow the forward movement of said input rod; a plunger connected to the input rod is slidably fitted in the front part of a tubular valve casing; a reaction disc mounted inside the valve body and is axially aligned with the plunger; characterized in that a plurality of covers of predetermined thickness are connected to outer surface of the plunger and inner surface of the valve body to vary boost ratio and jump-in of the brake booster.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The novel features and characteristics of the disclosure are set forth in the
appended claims. 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:
FIG. 1 shows sectional view of brake booster device according to the prior art.
FIG. 2 shows sectional view of assembly of the valve body with the plunger
according to the prior art.
FIG. 3 shows exploded view of the valve body, the reaction disc and the
plunger according to the prior art.
FIG. 4 shows sectional view of a brake booster device according to an
embodiment of the disclosure.
FIGS. 4a, 5a and 5b show sectional views of assembly of the valve body with
the plunger according to the disclosure.

FIGS. 6a and 6b show sectional views of assembly of the valve body with
threaded plunger for connectivity with cover according to the disclosure.
FIG. 7 shows exploded view of the valve body, the reaction disc, the plunger
and the plunger cover and valve body cover according to the disclosure.
FIGS. 8a, 8b and 8c show various views of both the covers according to the
disclosure.
FIG. 9 shows sectional view of the brake booster device according to the
disclosure.
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 structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying
figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, and figures are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
This disclosure is drawn, inter-alia, to brake booster device, a method of varying boost ratio, Jump-in and a method of assembling.
FIGS. 4, 4a, 5a, and 5b illustrate various sectional views of an assembly of the valve body (7a), the plunger (9a) along with a first cover (13a) and a second cover (14a). The first cover (13a) and a second cover (14a), also referred to as covers (13a, 14a) are mounted between the valve body (7a) and the plunger

(9a). The cover (14a) according to boost ratio requirement is assembled on the valve body (7a). The cover (14a) is a cylinder body having a stepped portion matching with a stepped portion of the valve body (7a) for proper locking in one direction. The cover (13a) is formed as a cylindrical cap with a side wall and an end wall. The cover (13a) mounted on the plunger (9a) has two configurations, wherein one configuration is to provide a fastening means (12a) connectivity between the cover (13a) and the plunger (9a). The fastening means (12a) is a fastener or screw. The other configuration (as illustrated in the FIGS. 6 and 6b) is to provide threading on outside surface of the plunger (9a) and on inside surface of the cover (13a). The cover (13a) can be attached to the plunger by any other suitable means also. The thickness of the side wall and end wall of the cover (13a) can be varied separately for varying boost ratio and jump-in independently. The thickness of the side wall of the cover (13a) is varied for varying the boost ratio corresponding to the thickness of the cover (14a) and the thickness of the end wall of the cover (13a) is varied for varying the jump-in. Thus, a required boost ratio and jump-in is provided using the valve body (7a) and the plunger (9a) along with the covers (13a, 14a). The variation in thickness of the covers 13a and 14a are mutually complementary to each other such that the total thickness of the covers 13a and 14a remains same. That is increase in thickness of one cover decreases the other cover thickness such that the total thickness of the covers remains same. The total thickness is decided by the designed diameter of the common valve body opening and common plunger outer diameter. The total thickness of the covers 13a and 14a is the radial distance between the plunger outer surface and inner surface of the valve body opening. Thickness of the end wall of the cover 13a will vary the jump-in as the distance between the reaction disc and cover 13a end point will vary accordingly. The valve body (7a) and the plunger (9a) are designed for maximum boost ratio and minimum boost ratio respectively for commonizing for different boost ratio requirement. The valve body with the cover (14a) creates an opening for receiving the plunger which decides the boost ratio. This opening can be varied by varying the thickness of the cover (14a) as per the required boost ratio. As the plunger is designed for minimum boost ratio this will create a gap between the valve body with cover and the plunger. The cover (13a) is attached to the plunger for bridging the gap between the valve body

with cover (14a) and the plunger. Total thickness of the cover (13a) on plunger and the cover (14a) on valve body is the gap between the common valve body and the plunger. The varying boost ratio can also be achieved by providing cover on either of the valve body or plunger. By providing cover only on valve body or plunger limit the commonization to that component and the other component dimension need to modify according to the requirement.
With reference to FIG. 7, the boost ratio is expressed as the ratio of square of reaction disc (11a) diameter (D) to the square of the cover (13a) diameter (d1).
Boost Ratio= [Reaction disc diameter (D)l2 (Eqn. 1)
[Cover diameter (d1)]2
The Jump-in is expressed as the gap between the reaction disc (11a) and the plunger (9a). Thus the required jump-in value is achieved by changing the plunger (9a) length (L3), as shown in FIG. 7. This is achieved by varying the thickness (L1) of the cover (13a) thereby adding addition length (L1) to the plunger. Also, the designing of separate valve body and plunger for the required boost ratio and jump-in in any given size of brake booster device like single or tandem brake booster device is overcome by the design of covers (13a, 14a).
FIGS. 8a, 8b and 8c shows various views of cover (14a) connected to the valve body (7a) and cover (13a) connected to the plunger (9a). The FIG. 8a illustrates cover (13a) comprising a drilled hole at its axis for fastening means (12a) to pass through. The FIG. 8b illustrates the cover (13b) without having a drilled hole, but being threaded internally to connect with the plunger (9a). The FIG. 8c illustrates the cover (14a) connected to the valve body (7a). The cover (14a) is made with threads on its outside surface for connecting with the valve body (7a). Optionally, the cover (14a) is inserted in the valve body (7a), wherein movement of the inserted cover (14a) is restricted by stepped portion of the valve body (7a) on one side and by the reaction disc (11a) abutting on other side of the cover (14a).

FIG. 9 also illustrates sectional view of brake booster device (1a) according to the disclosure. The brake booster device (1a) comprises a booster body (2a); a booster piston (3a) accommodated in the booster body (2a). A diaphragm (4a) is connected to a booster piston (3a) for dividing the booster body (2a) into front (5a) and rear working chambers (6a). The front working chamber (5a) is communicating with a vacuum supply source. The rear working chamber (6a) is selectively communicating with the front working chamber (5a) or external atmosphere through a valve body (7a). An input rod (8a) is located opposite to the booster piston (3a) for movement toward and away from the booster piston (3a). The input rod (8a) is connected to the valve body (7a) to produce a pressure difference between the working chambers (5a, 6a) and thus activating the booster piston (3a) to follow the forward movement of the input rod (8a). A plunger (9a) is connected to the input rod (8a) and is slidably fitted in the front part of a tubular valve casing (10a). A reaction disc (11a) is mounted inside the valve body (7a) and is axially aligned with the plunger (9a). At least one cover of required thickness is connected to outer surface of the plunger (9a) and inner surface of the valve body (7a) to vary boost ratio and jump-in of the brake booster (1a).
Advantages
1. In one embodiment, the brake booster device as disclosed herein reduces variety of the valve bodies for various boost ratio, thereby reducing complexity of the valve body manufacturing, tooling, inventory, and mix-up.
2. In one embodiment, the brake booster device as disclosed herein decreases development cost and time since there is no development required in the valve body and also the valve body is used as a carryover part in all sizes of the brake booster device.
3. In one embodiment, the brake booster device as disclosed herein uses covers in all sizes of the brake booster device to obtain required boost ratio and jump-in by changing dimensions/thickness of the covers.
4. In one embodiment, the brake booster device as disclosed herein uses common valve body and plunger irrespective of brake booster device size.

5. In one embodiment, the brake booster device as disclosed herein obtains required boost ratio in a given brake booster device using the valve body, the plunger and by varying diameters of the covers.
6. In one embodiment, the brake booster device as disclosed herein obtains required jump-in in any given brake booster device using the valve body, the plunger and by varying length of the cover (13a).
Industrial Applicability
The disclosed brake booster device finds potential application in any brake system where boost ratio and jump-in customization is desirable. The disclosed brake booster device finds particular applicability in hydraulic brake systems. One skilled in the art will recognize, however, that the disclosed brake booster device having the modified plunger, modified valve body and covers with various sizes, could be utilized in relation to other systems that may or may not be associated with brake systems.
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 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.
Referral numerals:
1: Booster device according to prior art.
2: Booster body according to prior art.
3: Booster piston according to prior art.
4: Diaphragm according to prior art.
5: Front working chamber according to prior art.
6: Rear working chamber according to prior art.
7: Valve body according to prior art.
8: Input rod according to prior art.
9: Plunger according to prior art.
10: Tubular valve casing according to prior art.
11: Reaction disc according to prior art.
1a: Booster device according to the disclosure.
2a: Booster body according to the disclosure.
3a: Booster piston according to the disclosure.
4a: Diaphragm according to the disclosure.
5a: Front working chamber according to the disclosure.
6a: Rear working chamber according to the disclosure.
7a: Valve body according to the disclosure.
8a: Input rod according to the disclosure.
9a: Plunger according to the disclosure.
10a: Tubular valve casing according to the disclosure.
11a: Reaction disc according to the disclosure.
12a: Fastening means according to the disclosure.
13a: Cover for the plunger according to the disclosure.
14a: Cover for the valve body according to the disclosure.

We claim:
1. A brake booster device (1a) comprising:
a. a booster body (2a);
b. a booster piston (3a) accommodated in said booster body (2a);
c. a diaphragm (4a) connected to said booster piston (3a) for dividing said
booster body (2a) into front (5a) and rear working chambers (6a), said
front working chamber (5a) communicating with a vacuum supply
source, said rear working chamber (6a) selectively communicating with
said front working chamber (5a) or external atmosphere through a valve
body (7a);
d. an input rod (8a) located opposite to said booster piston (3a) for
movement toward and away from said booster piston (3a), said input rod
(8a) being connected to said valve body (7a) to produce a pressure
difference between said working chambers (5a, 6a) for causing said
booster piston (3a) to follow the forward movement of said input rod
(8a);
e. a plunger (9a) connected to said input rod (8a) is slidably fitted in a front
part of a tubular valve casing (1 Oa);
f. a reaction disc (11a) mounted inside said valve body (7a) and is axially
aligned with said plunger (9a);
characterized in that
a first cover (13a) of predetermined thickness connected to an outer surface of said plunger (9a) and/or a second cover (14a) of predetermined thickness connected to an inner surface of said valve body (7a), to vary boost ratio and jump-in of said brake booster device (1a).
2. The brake booster device (1a) as claimed in claim 1, where a total thickness of said cover (13a) on said plunger (9a) and said cover (14a) on said valve body (7a) is equal to radial gap between said valve body (7a) and said plunger (9a).
3. The brake booster device (1a) as claimed in claim 1, wherein the variation in thickness of the covers 13a and 14a are mutually complementary to each

other such that said total thickness of said covers 13a and 14a remains same, and equal to said gap.
4. The brake booster device (1a) as claimed in claim 1, wherein said first cover (13a) having predetermined thickness is fixed onto a front end of said plunger (9a) using a fastener.
5. The brake booster device (1a) as claimed in claim 4, wherein the thickness of said cover (13a) is varied along axis of said brake booster device (1a) to vary jump-in of said brake booster device (1a).
6. The brake booster device (1a) as claimed in claim 3, wherein said plunger (9a) is threaded on its outer surface for connecting said cover (13a) with the plunger (9a).
7. The brake booster device (1a) as claimed in claim 1, wherein the inner surface of said valve body (7a) is threaded for connecting a cover (14a) of predetermined thickness to said valve body (7a).
8. The brake booster device (1a) as claimed in claim 1, wherein a cover (13a) is connected to said plunger (9a) using a fastener or threads made on said plunger (9a).
9. The brake booster device (1a) as claimed in claim 1, wherein a cover (14a) is connected to said valve body (7a) through threads made on said valve body (7a) or inserted in said valve body (7a).