Claims:1. An improved cable mechanism (40) for a parking brake of a vehicle comprises:
an inner core cable (21) configured for connecting to a parking brake lever at one end and another end connected to a wheel brake;
a plurality of outer casing segments (22a & 22b) configured for enclosing the said inner core cable (21); and
at least one ball bearing unit (41) configured to connect two adjacent outer casing segments (22a & 22b) to form an integral outer casing (22).

2. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein said ball bearing unit (41) comprises a housing (51) having a central cylindrical portion (52) and conical portions (53) at both the ends of the central cylindrical portion (52).

3. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein the central cylindrical portion (52) of said ball bearing unit (41) is configured with plurality of circumferential grooves (54) on inner surface of the central cylindrical portion (52) to accommodate plurality of roller balls (55).

4. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein the conical portions (53) are configured to be crimped on the respective ends of the adjacent outer casing segments (22a & 22b) to form rigid joint between two outer casing segments (22a & 22b).

5. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein a circumferential slot (56) is configured on the outer surface of the housing (51) for mounting a clamp to rigidly secure the said ball bearing unit (41) on vehicle underbody.

6. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein the circumferential grooves (54) provided on the inner surface of the central cylindrical portion (52) are configured for accommodating plurality of roller balls (55) to constitute a ball bearing unit.

7. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein the inner core cable (21) is configured to be in point contact with each roller balls (55) for reducing the friction between the inner core cable (21) and outer casing (22).

8. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein said ball bearing unit (41) is configured to be mounted near the bend of the parking cable to reduce the friction between the inner core cable (21) and outer casing (22).

9. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein plurality of ball bearing units (41) throughout the parking brake cable are configured to reduce the effort required for actuation of the parking brake and also to reduce parking brake noise.

10. The improved cable mechanism (40) for a parking brake of a vehicle as claimed in claim 1, wherein plurality of ball bearing units (41) throughout the parking brake cable are configured to improve load efficiency of the parking brake cable. , Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
AN IMPROVED CABLE MECHANISM FOR PARKING BRAKE

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400001, Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD OF THE PRESENT INVENTION
[001] The present subject matter described herein, in general relates to a cable mechanism for vehicle parking brake system. More particularly the subject matter relates to an improved cable mechanism to reduce parking brake effort and noise.

BACKGROUND OF THE PRESENT INVENTION
[002] In vehicles, a parking brake system is used to ensure that the parked vehicle stays in place or stays motionless, especially on hills and other declines. When the parking brake is engaged, it locks the wheels in place to ensure that the vehicle doesn’t roll away. A cable type hand actuated parking brake is prominently used in vehicles to apply brakes to mostly rear wheels. While a parking brake isn’t required to be engaged for the vehicle to stay stopped, it works to prevent vehicle from rolling, especially on steep inclines.
[003] The parking brake system, as shown in figure 1, consists of a parking brake lever (10) provided in the cabin of the vehicle to engage and disengage the parking brake, an equalizer (not shown) and steel cables also referred to as parking brake cables (11) to connect the parking brake lever (10) to the main brakes of the vehicle located in the rear wheels. As shown in figure 2, a typical conventional parking brake cable (11) includes an inner core cable (21) sliding in an outer casing (22). One end of the cable (11) is attached to the parking brake lever (10) and another end of the cable is connected to rear wheel brake. Thus, the parking brake cable has to be routed from the parking brake lever (10) in the cabin to the rear brakes of rear wheels. While sliding inside the outer casing (22), the inner core cable (21) touches the outer casing (22) creating noise and friction across the friction area (23).
[004] The performance of parking brake system depends on the efficiencies of the parking brake cable, parking lever linkage and rear brake. Whereas, the performance of parking brake actuation system depends on cable routing, cable selection, linkage ratio etc. Figure 3 depicts the parking brake cable layout. It is seen in figure 3 that the parking brake cables (11) needs to be bent at multiple locations for routing the same on the vehicle underbody. It is observed that the friction between the inner core cable and outer housing is maximum near these bend sections. Moreover, various parameters are considered to calculate load and stroke of parking brake such as diameter of inner core cable & outer casing, coefficient of friction, stiffness, bend angle & bend radius of routed cable, clearance between inner core cable and outer casing, material of cable etc.
[005] The effort required for actuation of parking brake plays very important role in driver comfort during parking of the vehicle. The parking brake effort is highly influenced by performance of the cable i.e., its load efficiency. If the load efficiency of the cable is low, higher effort is required to actuate the parking brake and this causes discomfort to the driver. Hence, there is a requirement of a parking brake system which will reduce the effort required for actuation of parking brake and increase its load efficiency.

OBJECTS OF THE PRESENT INVENTION
[006] Main object of the invention is to provide an improved cable mechanism for a parking brake system of vehicle.
[007] Another object of the invention is to provide an improved cable mechanism for reducing parking brake effort and parking brake noise.
[008] Yet another object of the invention is to provide an improved cable mechanism to efficiently reduce friction between inner core cable and outer casing of a parking cable.
[009] Yet another object of the invention is to provide an improved cable mechanism to efficiently reduce friction between inner core cable and outer casing of a parking cable by introducing point contacts between an inner core cable and an outer casing of a parking brake instead of conventional surface contact.
[0010] Yet another object of the invention is to provide an improved cable mechanism for comfort of the driver while parking a vehicle by improving load efficiency of the parking brake cable.

SUMMARY OF THE PRESENT INVENTION
[0011] Before the present system is described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosure. It is also to be understood that the terminologies used in the description is for the purpose of describing the particular version or embodiment only and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to an improved cable mechanism for a parking brake system and the aspects are further elaborated below in the detailed application description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[0012] The present subject matter discloses an improved cable mechanism for a vehicle parking brake. The improved cable mechanism comprises an inner core cable, plurality of outer casing segments and a ball bearing unit. The ball bearing unit includes a housing with central cylindrical portion and conical portions at both the ends. The conical portions of the housing are crimped on the respective ends of the outer casing segments to form rigid joint between the outer casing segments. Plurality of circumferential grooves are provided on inner surface of the central cylindrical portion to accommodate plurality of roller balls. Thus, the inner core cable is in point contact with each roller balls thereby reducing the friction between the inner core cable and the outer casing segments. Moreover, a circumferential slot is provided on outer surface of the housing for mounting a clamp to secure the ball bearing unit on vehicle underbody.

STATEMNT OF THE PRESENT INVENTION
[0013] The present subject matter discloses an improved cable mechanism for a parking brake of a vehicle. The improved cable mechanism comprises an inner core cable, plurality of outer casing segments and a ball bearing unit. The inner core cable is configured to be connected to a parking brake lever at one end and a wheel brake at another end. The outer casing segments are configured to enclose the inner core cable. The ball bearing unit is configured to connect two adjacent casing segments to form an integral outer casing. The ball bearing unit comprises a housing having a central cylindrical portion and conical portions at both the ends of the central cylindrical portion. The central cylindrical portion of the ball bearing unit is configured with plurality of circumferential grooves on inner surface of the central cylindrical portion to accommodate plurality of roller balls.
[0014] The conical portions of the housing are configured to be crimped on the respective ends of the outer casing segments to form rigid joint between the two outer casing segments. A circumferential slot is configured on the outer surface of the housing for mounting a clamp to rigidly secure the said ball bearing unit on vehicle underbody. The circumferential grooves provided on the inner surface of the central cylindrical portion are configured for accommodating plurality of roller balls to constitute a ball bearing unit. The inner core cable is configured to be in point contact with each roller balls for reducing the friction between the inner core cable and outer casing. The ball bearing unit is configured to be mounted near the bend of the parking cable to reduce the friction between the inner core cable and outer casing. Plurality of ball bearing units throughout the parking brake cable are configured to reduce the effort required for actuation of the parking brake and also to reduce parking brake noise. Plurality of ball bearing units throughout the parking brake cable are configured to improve load efficiency of the parking brake cable.

BRIEF DESCRIPTION OF DRAWINGS
[0015] The foregoing summary, as well as the following detailed description of embodiment, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing.
[0016] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0017] Figure 1 illustrates a schematic view of a parking brake system with a parking brake lever and a parking brake cable (Prior art).
[0018] Figure 2 illustrates a sectional view of a parking brake cable (Prior art).
[0019] Figure 3 illustrates a schematic view of a parking brake cable layout which includes parking brake cables routed on vehicle underbody (Prior Art).
[0020] Figure 4 illustrates an isometric view of an improved cable mechanism, in accordance to the present disclosure.
[0021] Figure 5 illustrates a sectional view of a ball bearing unit connecting two outer casing segments, in accordance to the present disclosure.
[0022] Figure 6 illustrates a schematic view of the parking brake cables operated by parking brake lever, in accordance to the present disclosure.
[0023] Figure 7 illustrates a schematic view of the parking brake cables routed on vehicle underbody, in accordance to the present disclosure
[0024] Figures depict various embodiments of the present disclosure for purpose of illustration only. Only skilled in the art will readily recognize from the following discussion 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 OF THE PRESENT INVENTION
[0025] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words “comprising”, “having”, and “including,” and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0026] Various modification to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to another embodiment. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
[0027] The disclosure herein provides an improved cable mechanism (40) for a parking brake system. Figure 4 illustrates a ball bearing unit (41) configured to connect two adjacent outer casing segments (22a & 22b) to form an integral outer casing (22) for the cable operated parking brake system. As illustrated in Figure 5, the ball bearing unit (41) comprises a housing (51) having a central cylindrical portion (52) and conical portions (53) at both the ends. Each conical portion (53) starts from each end of central cylindrical portion (52) and converges towards the axis of the central cylindrical portion (52) such that the outer casing segments (22a or 22b) are received axially in the conical portions (53) to form a rigid joint between the two outer casing segments (22a & 22b) by crimping the ends of conical portions (53) on the respective ends of adjacent outer segments (22a & 22b). Plurality of circumferential grooves (54) are configured on inner surface of the central cylindrical portion (52) for accommodating plurality of roller balls (55) in similar fashion as in the conventional bearings. A circumferential slot (56) is configured on outer surface of the housing (51) for mounting a clamp for rigidly securing the ball bearing unit (41) of the improved cable mechanism (40) on the vehicle underbody.
[0028] When the inner core cable (21) is inserted in the integral outer casing (22), it passes through the ball bearing unit (41). The friction between the inner core cable (21) and the outer casing segments (22a & 22b) is reduced considerably due to point contact between the roller balls (55) and the inner core cable (21) instead of conventional surface contact between the inner core cable (21) and outer casing (22).
[0029] Thus, providing the ball bearing unit (41) at multiple locations in parking brake layout reduces the friction between the inner core cable (21) and the integral outer housing (22) thereby reducing parking brake effort and parking brake noise. The locations of the ball bearing units (41) in the parking brake system are most preferably selected by identifying maximum friction areas such as bends or curves of the parking brake cable as shown in Figure 6 and Figure 7.
[0030] Accordingly, the present invention discloses an improved cable mechanism (40) for a parking brake of a vehicle comprises an inner core cable (21) configured for connecting to a parking brake lever at one end and another end connected to a wheel brake, a plurality of outer casing segments (22a & 22b) configured for enclosing the said inner core cable (21), and at least one ball bearing unit (41) configured to connect two adjacent outer casing segments (22a & 22b) to form an integral outer casing (22). The ball bearing unit (41) comprises a housing (51) having a central cylindrical portion (52) and conical portions (53) at both the ends of the central cylindrical portion (52). The central cylindrical portion (52) of said ball bearing unit (41) is configured with plurality of circumferential grooves (54) on inner surface of the central cylindrical portion (52) to accommodate plurality of roller balls (55). The conical portions (53) are configured to be crimped on the respective ends of the adjacent outer casing segments (22a & 22b) to form rigid joint between two outer casing segments (22a & 22b). A circumferential slot (56) is configured on the outer surface of the housing (51) for mounting a clamp to rigidly secure the said ball bearing unit (41) on vehicle underbody. The circumferential grooves (54) provided on the inner surface of the central cylindrical portion (52) are configured for accommodating plurality of roller balls (55) to constitute a ball bearing unit. The inner core cable (21) is configured to be in point contact with each roller balls (55) for reducing the friction between the inner core cable (21) and outer casing (22). The ball bearing unit (41) is configured to be mounted near the bend of the parking cable to reduce the friction between the inner core cable (21) and outer casing (22). Plurality of ball bearing units (41) throughout the parking brake cable are configured to reduce the effort required for actuation of the parking brake and also to reduce parking brake noise. Plurality of ball bearing units (41) throughout the parking brake cable are configured to improve load efficiency of the parking brake cable.
[0031] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0032] Some embodiments provide an improved cable mechanism for reducing parking brake effort and parking brake noise.
[0033] Some embodiments provide an improved cable mechanism to efficiently reduce friction between inner core cable and outer casing of a parking cable.
[0034] Some embodiments provide an improved cable mechanism for comfort of the driver while parking a vehicle by improving load efficiency of the parking brake cable.
[0035] Although implementations for a parking brake system have been described in language specific to structural features, it is to be understood that the appended claims are not necessarily limited to the specific features described. Rather, the specific features are disclosed as examples of implementation for the parking brake system.
[0036] Figures 1-7 are now described using the reference numbers stated in the below table.
[0037] REFERRAL NUMERALS:
Element Description Reference Numeral
Parking brake lever 10
Parking brake cables 11
Inner core cable 21
Outer casing 22
Outer casing segments 22a & 22b
Friction area 23
Improved cable mechanism 40
Ball bearing unit 41
Housing 51
Central cylindrical portion 52
Conical portions 53
Circumferential grooves 54
Roller balls 55
Circumferential slot 56