Claims:
1. A hydraulic drum brake (90) for a motor vehicle braking system (500) comprising a back plate (120), a wheel cylinder assembly (100, 110), a conventional fixing means (130) for attaching the wheel cylinders assembly (100, 110) to the back plate (120), a brake shoe (160, 170), a pivot point (250, 260) for providing a pivot for the brake shoe (160, 170), an adjuster (210), an adjuster spring (220) provided with the adjuster (210) for maintaining gap between the brake shoe (160, 170) and the brake drum (175), a main spring (200) attached to the brake shoe (160, 170) wherein the wheel cylinder assembly (100) is provided with a piston stopper structure (140) on the inner side of a wheel cylinder body (340) and the wheel cylinder assembly (110) is provided with a projection (230, 240) directly on a wheel cylinder body (390).

2. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the brake shoe (160, 170) is provided with a projection (161, 171) which interacts with the projection (230, 240) provided on the wheel cylinder body (390) of the wheel cylinder assembly (110).

3. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the adjuster (210) assembly is positioned along the wheel cylinder assembly (100).

4. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the wheel cylinder assembly (100, 110) with a wheel cylinder body (340, 390) is provided with a protection boot (330, 380).

5. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the wheel cylinder assembly (100, 110) with said wheel cylinder body (340, 390) is provided with a wheel cylinder seal (350, 400).

6. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the wheel cylinder assembly (100, 110) with said wheel cylinder body (340, 390) is provided with a wheel cylinder piston (360, 410).

7. A hydraulic drum brake (90) for a motor vehicle braking system (500) as claimed in claim 1, wherein the wheel cylinder assembly (100, 110) with said wheel cylinder body (340, 390) is provided with a rebound spring (370, 420).
, Description:FIELD OF THE INVENTION
The present invention relates to drum brakes for motor vehicles. It more particularly relates to hydraulic drum brakes which are variously utilisable with different braking systems.
BACKGROUND OF THE INVENTION
It is known that a motor vehicle can be provided with more than one braking circuit to improve safety and reliability of braking. In some countries it is even an essential requirement that such separate braking circuits be provided in motor vehicles. Conventionally, separate actuation means are provided for the separate braking circuits in two wheeler motor vehicles.
The operation of front wheel brake with some time lag following the application of rear wheel brake helps the motor vehicle operator to retain greater control over the motor vehicle in a situation requiring combined application of both front and rear wheel brakes. Braking systems such as Combined Braking System (CBS) which already exist in the prior art, are capable of synchronising the operation of front and rear wheel brake circuits to achieve improvement resulting from synchronised operation of brakes. Furthermore, braking control systems such as Anti-lock Braking System (ABS), Traction Control System (TCS) and Electronic Stability Control (ESC) have also been developed to improve the control of the operator over the motor vehicle. These systems prevent slipping of the wheels and maintain stability in different circumstances that may arise during motor vehicle operation. It is known that these systems are capable of being utilised in combination with disc or drum brakes to provide optimal braking performance.
Conventionally, the front and rear brakes in a motor vehicle could be either drum (mechanical or hydraulic type) or disc brakes depending on engineering and economic considerations. Disc and drum brakes are also known to be used in combination in motor vehicles for optimally balancing the requirement of safety and economy. Existing combined braking system generally incorporate various combinations of hydraulically operated disc brake on front or rear wheel braking system and mechanically operated drum brake on rear or front wheel braking system. Some such existing combined braking system are:
• Front and rear both hydraulically operated disc brake with a CBS actuating means provided on foot pedal/handlebar.
• Front and rear both mechanically operated drum brake with a CBS actuating means provided on foot pedal/handlebar.
• Front hydraulically operated disc brake and rear mechanically operated drum brake with a CBS actuating means provided on foot pedal.
• Front hydraulically operated disc brake and rear hydraulically operated drum brake with a CBS actuating means provided on foot pedal as disclosed in 3130/MUM/2015.
One technical problem in the prior art is that in a motor vehicle especially two-wheeler, hydraulic drum brakes are not used on the front wheel along with combined braking system. This is in part a consequence of conventional hydraulic drum brake units not having suitable means to isolate and effectively utilise braking inputs being provided by two different actuation means situated differently on the motor vehicle body. Even otherwise, drum brakes in general are considered less suitable for utilisation as front wheel brakes in comparison with disc brakes due to their other known existing limitations. The problem of wheel grabbing experienced by drum brakes in certain circumstances specifically requires effective management. The present invention aims to overcome the limitations while also further enabling utilisation of drum brakes in combination with other braking control systems as well.
It is an objective of the current invention to provide a front braking means incorporating drum brake with two wheel cylinders for facilitating separate front brake application and a separate combined brake application.
It is another objective of the current invention to provide hydraulically operated drum brake readily adaptable to be used as front wheel braking means that is adaptable with disc brake or drum brake as rear braking means.
It is further an objective of the present invention to provide a drum brake capable of being variously utilisable in combination with different braking control systems.
It is yet another objective of the present invention to provide a braking system capable of overcoming the disadvantage of low braking force prevalent in drum brakes.
It is still another objective of the present invention to utilise the simple design characteristics of drum brake in the front braking system while providing two wheel cylinders in it.
It is one more objective of the current invention to provide safe braking means for use in motor vehicles.
SUMMARY OF THE INVENTION
With above objectives in view, the current invention provides a hydraulic drum brake (90) for a motor vehicle braking system (500) comprising of a back plate (120), a wheel cylinder assembly (100, 110), a conventional fixing means (130) for attaching the wheel cylinders assembly (100, 110) to the back plate (120), a brake shoe (160, 170), a pivot point (250, 260) for providing a pivot for the brake shoe (160, 170), an adjuster (210), an adjuster spring (220) provided with the adjuster (210) for maintaining gap between the brake shoe (160, 170) and the brake drum (175), a main spring (200) attached to the brake shoe (160, 170) wherein the wheel cylinder assembly (100) is provided with a piston stopper structure (140) on the inner side of a wheel cylinder body (340) and the wheel cylinder assembly (110) is provided with a projection (230, 240) directly on a wheel cylinder body (390).
Typically, the brake shoe (160,170) is provided with a projection (161,171) which interacts with the projection (230, 240) provided on the wheel cylinder body (390) of the wheel cylinder assembly (110).
Typically, the adjuster (210) assembly is positioned along the wheel cylinder assembly (100).
Typically, the wheel cylinder assembly (100, 110) of the hydraulic drum brake (90) is provided with a protection boot (330, 380).
Typically, the wheel cylinder assembly (100, 110) of the hydraulic drum brake (90) is further provided with a wheel cylinder seal (350, 400).
Typically, the wheel cylinder assembly (100, 110) of the hydraulic drum brake (90) is further provided with a wheel cylinder piston (360, 410).
Typically, the wheel cylinder assembly (100, 110) is also provided with a rebound spring (370, 420).
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates the front view of the hydraulic drum brake in accordance with the current invention
Figure 2 illustrates the sectional view of the hydraulic drum brake in accordance with the current invention
Figure 3 illustrates a scaled down three dimensional view of hydraulic drum brake in accordance with the current invention
Figure 4 illustrates a motor vehicle braking system with hydraulic drum brake as per the current invention
Figure 5 illustrates the second embodiment of a motor vehicle braking system with hydraulic drum brake as per the current invention
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiment of the hydraulic drum brake for a motor vehicle braking system in accordance with the current invention will now be described in detail with reference to the accompanying diagrams. The preferred embodiment disclosed must not be viewed as restricting the scope and ambit of the claims.
Figure 1 illustrates the front view of the hydraulic drum brake (90) in accordance with the current invention. The hydraulic drum brake (90) is a lead-lead type drum brake. According to the Figure 1, the wheel cylinder assembly (100) and the wheel cylinder assembly (110) are fixed on a back plate (120) of the hydraulic drum brake (90) of said front wheel brake (10) by a conventional fixing means (130) (not specifically indicated). A main spring (200) is provided between a brake shoe (160) and a brake shoe (170) to provide the restoring force for returning of the brake shoe (160) and the brake shoe (170) to their original position after the brake is released. The brake shoe (160) and said brake shoe (170) are interlinked by an adjuster (210), and said adjuster (210) and said brake shoe (160) are so structured so as to be further operationally linked by an adjuster spring (220). The adjuster (210) assembly is in its entirety positioned along the wheel cylinder assembly (100). The adjuster (210) allows the position of the brake shoe (160, 170) to be adjusted to be accommodated for its wear due to friction. A pivot pin shoe (310) is provided along with a spring shoe clamping (320) on the brake shoe (160) and the brake shoe (170). The pivot pin shoe (310) functions to fix the spring shoe clamping (320) over the brake shoe (160, 170). The brake shoe (160) is free to rotatably move on the pivot point (250), while the brake shoe (170) is free rotatably move on the pivot point (260) (as indicated in Figure 2). The pivot point (250, 260) enables the brake shoe (160, 170) to come in contact with the brake drum (175) when either one or both of the wheel cylinder assembly (100) and the wheel cylinder assembly (110) are operated.
Figure 2 illustrates the sectional view of drum brake (90) in accordance with the current invention. Figure 2 illustrates a piston stopper structure (140) provided inside said wheel cylinder assembly (100). The piston stopper structure (140) corresponds to the increased inner diameter portion provided inside the wheel cylinder assembly (100) in the middle of the wheel cylinder of wheel cylinder assembly (100). The piston stopper structure (140) inside said wheel cylinder assembly (100) enables the point of contact between a piston head (145) and a brake shoe (160) to function as an anchoring point (180) when said wheel cylinder assembly (110) is operated due to operation of a brake actuating means (50) (as indicated in Figure 4 and Figure 5). The piston stopper structure (140) also enables a piston head (150) and a brake shoe (170) to function as an anchoring point (190) when said wheel cylinder assembly (110) is operated due to operation of said brake actuating means (50). Furthermore, the brake shoe (160) pivots at a pivot point (250), while the brake shoe (170) pivots at a pivot point (260) as indicated in Figure 2. The brake shoe (160) and the brake shoe (170) hence come into contact with a brake drum (175) upon operation of the brake actuating means (50). The anchoring point (180) provides anchoring point for guiding the movement of the brake shoe (160) and the anchoring point (190) provides anchoring points for guiding the movement of the brake shoe (170) resulting in braking of the motor vehicle upon operation of the brake actuating means (50) by the motor vehicle operator.
Furthermore in Figure 2, as illustrated the wheel cylinder assembly (110) is provided with a rigid external structure which provides a projection (230) for functioning as an anchoring point for said brake shoe (160) and a projection (240) for functioning as an anchoring point for said brake shoe (170) when said wheel cylinder assembly (100) is operated upon operation of a brake actuating means (30) (as indicated in Figure 4 and Figure 5). The brake shoe (160, 170) is provided with a projection (161, 171). The projection (161, 171) interacts with the projection (230, 240) provided on the wheel cylinder body (390) of the wheel cylinder assembly (110) when the brake actuating means (30) is operated. The brake shoe (160, 170) pivots at a pivot point (250, 260) provided in the hydraulic drum brake (90). The brake shoe (160, 170) hence come into contact with the brake drum (175) upon operation of the brake actuating means (30) with the projection (230, 240) providing the anchoring points for guiding the movement of the brake shoe (160, 170), resulting in braking of the motor vehicle.
The wheel cylinder assembly (110) illustrated in Figure 2 is provided with a protection boot (380), a wheel cylinder body (390), a wheel cylinder seal (400), a wheel cylinder piston (410) and a rebound spring (420). The operation of the brake actuating means (50) causes hydraulic pressure to develop inside the wheel cylinder assembly (110) which then causes the wheel cylinder piston (410) to move outwards. A wheel cylinder seal (400) prevents the leakage of hydraulic fluid from the wheel cylinder assembly (110). A rebound spring (420) provides the necessary force to push the wheel cylinder piston (410) outwards so that it remains in contact with the brake shoe (170). It is stated that corresponding components on Left Hand Side (LHS) of the wheel cylinder assembly (110) have the same structure and function.
The wheel cylinder assembly (100) illustrated in Figure 2, is also provided with a protection boot (330), a wheel cylinder body (340), a wheel cylinder seal (350), a wheel cylinder piston (360), a rebound spring (370). The operation of the brake actuating means (30) causes a hydraulic pressure to develop inside the wheel cylinder assembly (100) which causes the wheel cylinder piston (360) to move outwards. A wheel cylinder seal (350) prevents the leakage of hydraulic fluid from the wheel cylinder assembly (100). A rebound spring (370) provides the necessary force to push the wheel cylinder piston (360) outwards so that it remains in contact with the brake shoe (170). It is stated that corresponding components on Left Hand Side (LHS) of the wheel cylinder assembly (100) have the same structure and function. Operation of the wheel cylinder assembly (100) and the wheel cylinder (110) together leads to the braking shoe (160, 170) pressing against the brake drum (175) more strongly as opposed to when either of the wheel cylinder assembly (100) or the wheel cylinder assembly (110) is operated alone.
Figure 3 illustrates a scaled down three dimensional view of hydraulic drum brake (90) in accordance with the disclosed invention. The hydraulic drum brake (90) is provided with a wheel cylinder assembly (100) hydraulically linked to said brake actuating means (30) and a wheel cylinder assembly (110) hydraulically linked to said front and rear linked braking device (80) which in turn is operationally connected to the brake actuating means (50). The hydraulic drum brake (90) enables utilisation of hydraulic drum brakes as front wheels brakes in motor vehicles with the motor vehicle braking system (500).
The Figure 4 illustrates a motor vehicle braking system (500) with a hydraulic drum brake (90) as per the current invention provided as a front wheel brake (10). The motor vehicle braking system (500) is a conventional Combined Braking System (CBS). The motor vehicle braking system (500) comprises of a front wheel brake (10), a rear wheel brake (20), a brake actuating means (30) axially supported by a lever holder (40) (not specifically indicated) for operating said front wheel brake (10), a brake actuating means (50) axially supported on lower part of a vehicle body (60) for operating said rear wheel brake (20), a hydraulic line (70) for hydraulically connecting said brake actuating means (30) with said front wheel brake (10), said brake actuating means (50) being connected to a front and rear linked braking device (80), wherein the front wheel brake (10) is a hydraulic drum brake (90) of with a wheel cylinder assembly (100) hydraulically linked to said brake actuating means (30) and a wheel cylinder assembly (110) hydraulically linked to said front and rear linked braking device (80) which is operationally connected to the brake actuating means (50). The front and rear linked braking device (80) in the motor vehicle braking system (500) ordinarily comprises of a master cylinder (270) with an integrated delay valve. The CBS master cylinder (270) with an integrated delay valve is in addition connected to an oil reservoir (85). The brake actuating means (30) is operationally connected to a front brake master cylinder (15). Furthermore the front brake master cylinder (15) is hydraulically connected to the wheel cylinder (100) of the front wheel brake (10).
The motor vehicle braking system (500) operates to apply the front wheel brake (10) and the rear wheel brake (20) when the motor vehicle operator operates the brake actuating means (50). The operation of the brake actuating means (50) causes a force to be applied on the piston (not specifically indicated) inside the assembly of CBS master cylinder (270). The application of force on the piston (not specifically indicated) which develops hydraulic pressure in a hydraulic line (290) and a hydraulic line (300). The development of hydraulic pressure in the hydraulic line (290) leads to the application of the rear wheel brake (20). The increase in pressure in the hydraulic line (300) is transmitted to wheel cylinder assembly (110) of the front wheel brake (10) which causes application of the front wheel brake (10). The front and rear linked braking device (80) causes the application of the front wheel brake (10) with a delay after application of the rear wheel brake (20). Ordinarily in the motor vehicle braking system (500), the rear wheel brake (20) can be a conventional disc brake or a drum brake of mechanical or hydraulic type. The operation of the brake actuating means (30) applies a force on the piston (not specifically indicated) in the assembly of the front brake master cylinder (15). The master cylinder (15) is hydraulically connected to the wheel cylinder assembly (100) by the hydraulic line (70). The force applied on the piston (not specifically indicated) in the assembly of the front brake master cylinder (15) causes hydraulic pressure to develop in the wheel cylinder assembly (100) of the front wheel brake (10). The hydraulic pressure hence developed by operation of the brake actuating means (30) causes the front wheel brake (10) to be applied.
The Figure 5 illustrates a second embodiment of the motor vehicle braking system (500) with a hydraulic drum brake (90) (as per the current invention) as a front wheel brake (10). The components provided in the motor vehicle braking system (500) disclosed in Figure 4, also utilised in the second embodiment of the motor vehicle braking system (500) illustrated in Figure 5 have been provided with the same reference number. In the second embodiment of the motor vehicle braking system (500) the front and rear linked braking device (80) comprises of the CBS master cylinder (270) and a device (280). The device (280) is a delay valve or a pressure distribution junction or pressure regulatory control valve depending upon the engineering requirement. The brake pedal (50) is operationally connected to the CBS master cylinder (270). The CBS master cylinder (270) is further hydraulically connected to the device (280). The device (280) in turn is hydraulically connected to the rear brake (20) via the hydraulic line (290). The device (280) is also hydraulically connected to the wheel cylinder assembly (110) of the front wheel brake (10) via the hydraulic line (300). The brake actuating means (30) is operationally connected to the front brake master cylinder (15) which in turn is hydraulically connected to the wheel cylinder assembly (100) of the front wheel brake (10) via the hydraulic line (70).
The second embodiment of the motor vehicle braking system (500) illustrated in Figure 5 functions to apply the front wheel brake (10) and the rear wheel brake (20) when the motor vehicle operator operates the brake actuating means (50). The brake actuating means (50) is operationally connected to the CBS master cylinder (270). The operation of brake actuation means (50) applies force on the master cylinder piston (not specifically indicated) inside the assembly of said CBS master cylinder (270) to develop hydraulic pressure required to apply. The device (280) hydraulically connected to the CBS master cylinder (270) transmits the increase in hydraulic pressure to the hydraulic line (290). The increased pressure in the hydraulic line (290) is transmitted to the rear wheel brake (20), causing the rear wheel brake (20) to be applied. The device (280) also transmits the increase in hydraulic pressure to the hydraulic line (300). The increase in hydraulic pressure in the hydraulic line (300) is transmitted to said wheel cylinder assembly (110) of the front wheel brake (10) causing it to be applied. The front and rear linked braking device (80) in the second embodiment of the motor vehicle braking system (500) comprises of the CBS master cylinder (270) and a device (280). The device (280) in the motor vehicle braking system (500) can either be a delay valve or a pressure distribution junction or pressure regulatory control valve depending upon engineering requirement. The front and rear linked braking device (80) causes the application of the front wheel brake (10) with a delay after application of rear wheel brake (20) when the device (280) is a delay valve. The front and rear linked braking device (80) functions to distribute the hydraulic fluid between the front wheel brake (10) and the rear wheel brake (20) when the device (280) is a pressure distribution junction. In the second embodiment of the motor vehicle brake cylinder (500) the rear wheel brake (20) can be a conventional disc brake or a drum brake of mechanical or hydraulic type. The operation of the brake actuating means (30) applies a force on the piston (not specifically indicated) in the assembly of the front brake master cylinder (15). The force applied on the piston (not specifically indicated) in the assembly of the front brake master cylinder (15) causes hydraulic pressure to develop in the wheel cylinder assembly (100) of the front wheel brake (10) via the hydraulic line (70). The hydraulic pressure hence created by operation of the brake actuating means (30) causes the front wheel brake (10) to be applied separately.
The provision of the wheel cylinder assembly (100, 110), the piston stopper structure (140) and the projection (230, 240) in the hydraulic drum brake (90) enables effective isolation and utilisation of braking inputs from different brake actuators situated differently on motor vehicle body. The hydraulic drum brake (90) is therefore capable of facilitating separate front wheel braking and a separate combined brake application. The features of the hydraulic drum brake (90) hence enable it to be utilised in motor vehicles with Combined Braking Systems (CBS). The hydraulic drum brake (90) is also variously utilisable in combination with other braking control systems as well due to its described features.
The fact that the hydraulic drum brake (90) is utilisable in combination with other braking control systems which prevent wheel slippage and maintain motor vehicle stability enables effective management of the problem of wheel grabbing which may happen while utilising drum brakes. The disclosed hydraulic drum brake (90) for motor vehicle braking system hence provides a safe braking means for utilisation in motor vehicles. The motor vehicle operator can operate the brake actuating means together to achieve a higher braking force with the hydraulic drum brake (90). The hydraulic drum brake (90) utilising two wheel cylinder assemblies (100, 110) hence also overcomes the problem of low braking force prevalent in conventional drum brakes. The hydraulic drum brake (90) therefore facilitates improvement in braking response in motor vehicles. The hydraulic drum brake (90) is also adaptable to serve as a rear wheel braking means. The ease of manufacture of the hydraulic drum brake (90) allows it to retain the economic advantage provided by conventional hydraulic drum brakes.
Although the subject matter has been described in considerable detail with reference to certain embodiments of the motor vehicle braking system (500) which is a Combined Braking System (CBS), the hydraulic drum brake (90) may also be variously used in combination with other braking control systems as well. It is stated that the motor vehicle braking system (500) can also be an Anti-lock Braking System (ABS), Traction Control System (TCS), an Electronic Stability Control (ESC) or as such any braking control system utilisable for meeting the safety requirement. As such, the spirit and scope of the appended claims should not be limited by the description provided herein.
LIST OF REFERENCE NUMERALS

10 Front wheel brake
15 Front brake master cylinder
20 Rear wheel brake
30 Brake actuating means
40 Brake lever holder
50 Brake actuating means
60 Vehicle body
70 Hydraulic line
80 Front & rear liked brake device
90 Hydraulic drum brake
100 Wheel cylinder assembly
110 Wheel cylinder assembly
120 Back plate
130 Convectional fixing means
140 Piston stopper structure
145 Piston head
150 Piston head
160 Brake shoe
161 Projection
170 Brake shoe
171 Projection
175 Brake drum
180 Anchoring point
190 Anchoring point
200 Main spring
210 Adjuster
220 Adjuster spring
230 Projection
240 Projection
250 Pivot point
260 Pivot point
270 CBS master cylinder
280 Device
290 Hydraulic line
300 Hydraulic line
310 Pivot pin shoe
320 Spring shoe clamping
330 Protection boot
340 Wheel cylinder body
350 Wheel cylinder seal
360 Wheel cylinder piston
370 Rebound spring
380 Protection boot
390 Wheel cylinder body
400 Wheel cylinder seal
410 Wheel cylinder piston
420 Rebound spring
500 Motor vehicle braking system