FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
"BRAKE CIRCUIT LAYOUT" 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
INVENTORS
Matin Shaikh, Madhusudhan Belsare
All Indian national
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
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Field of Invention
This invention in general relates to vehicle braking circuit and in particular relates to a brake caliper adapted for use in such a vehicle braking circuit.
Background
Vehicles are enabled with a brake system for slowing or stopping motion of the vehicle in a controlled manner. Most vehicles include a disc brake assembly for each of the front wheels and a drum or disc brake assembly for each of the rear wheels. Actuation of such brake assemblies is generally achieved by hydraulic or pneumatic pressure generated when a brake pedal is depressed. Method and system of operation of such brake assemblies and their construction is well known in the art.
A brake caliper is part of a disc brake assembly that holds the brake shoes/pads and presses the disc when actuated. The brake pads press against the disc thereby enabling to slow or stop the vehicle.
The braking system 100 as shown in Fig.l for vehicles that are used for carriage of goods and having a maximum carrying capacity not exceeding 3.5 tonnes (Nl category) usually consists of front disc brake with twin-pot brake caliper 101 & 102 and rear drum brakes 111 & 112.. In such braking system, the hydraulic pressure is applied from the tandem master cylinder 105 to the front disc brakes 101 & 102 and rear drum brakes 111 & 112 through suitable flexible hoses 103 & 110. On application of hydraulic pressure, the piston (not shown in Figure) inside the wheel cylinders move out, thus pressing the brake shoes/pads against the discs/drums and thereby applying the brakes. To reduce the brake pedal effort, a twin diaphragm vacuum booster 106 is fitted between brake pedal (not shown in Figure) and tandem master cylinder (TMC) 105. The vacuum
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booster 106, provide a "boost ratio" defined as the ratio of the booster output to the booster input, of 3.5 to 7 times the effort produced by the driver thereby remarkably increasing the driver comfort. A push rod 122 (as shown in Fig.2) that connects the booster 106 and the brake pedal (not shown in Figure) is designed in such a manner that even in case of failure of the booster 106, the push rod 122 still transfers force mechanically to TMC piston. Vacuum to such a booster 106 is usually provided by a vacuum pump 116 (shown in Fig.2) connected by means of a vacuum hose 107. Load conscious pressure reducing valve (LCRV) 109 is generally provided in rear brake circuit to avoid locking of rear wheels and skidding of the vehicle.
In the braking circuit of prior art (Nl category) as described above, on depressing the brake pedal, pressurized fluid is supplied to the two rear wheel cylinders to enable stopping of vehicle. Thus the load on the front side of the vehicle increases than that of the rear side, this causes rear wheel locking. On utilizing such a braking circuit for vehicles that are used for the carriage of passengers and comprising no more than eight seats in addition to driver's seat (Ml category), the required mean fully developed deceleration
(MFDD) is not met. Usually a MFDD of 5.1 m/sec2 is required for stopping the vehicle in case of Nl category as compared to a MFDD requirement of about 5.91 m/sec2 for stopping the vehicle in case of Ml category. The aforesaid norms are based on European and IS vehicle braking regulations.
Thus meeting the Ml category norms with existing braking circuit is not possible due to the vehicle geometry and vehicle weight distribution (unladen Front axle weight/Rear axle weight) (F/R).
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There is therefore a need to provide a braking circuit for a Ml category vehicle that overcomes the abovementioned problems.
Object of the Invention
An object of the present invention is to provide a braking circuit that would meet the regulations of a Ml category vehicle.
Another object of the present invention is to provide a braking circuit that achieves the required MFDD for a Ml category vehicle.
Yet another object of the present invention is to provide a twin-pot brake caliper adapted for achieving a differential braking system along with rear brakes of Ml category vehicle.
Further object of the present invention is to overcome rear wheel locking.
Still further object of the present invention is to increase tire adhesion utilization deceleration thereby achieving cost reduction.
Although the present invention has been described with reference to certain embodiments as hereinafter, the invention is not limited to the embodiments. Various other embodiments of the invention will be apparent to a person skilled in the art or follow from routine experimentation.
Description
Fig.2 shows a layout of a modified braking circuit 100A with twin-pot brake calipers in accordance with one embodiment of the present invention. The modified braking circuit 100A comprises a disc brake with a twin-pot brake caliper 101 attached to the front RH wheel. Another disc brake with a twin-pot brake caliper 102 is attached to
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the front LH wheel. Both the twin-pot brake calipers comprise two bleeding nipples 120 & 121 and two hydraulic pressure intakes (not shown in Figure). On depressing of brake pedal (not shown in Figure), hydraulic fluid that is stored in a brake fluid bottle with automatic level indicator within a reservoir 113 (shown in Fig.l) is supplied to the bleeding nipples 120 & 121 of the front disc brakes 101 & 102 by means of brake hoses 103 & 114 that are connected to brake pipes 115 & 104 via T-connectors 122 & 123 respectively. The front brake pipe 1 115 is connected at a secondary port 118 of the TMC 105 and delivers brake fluid to the trailing caliper connected by bleeding nipple 121. The secondary port 118 thus ensures that brake fluid will be constantly supplied to the trailing caliper even on failure of primary port 119. Front brake pipe 104 is connected to primary port 119 of the TMC 105 by means of two T-connectors joining the rear brake pipe 108. Primary port ensures that braking fluid is supplied to rear drum brakes 111 & 112 through rear brake pipe 108 and to leading caliper of the front disc brake through front brake pipe 104.
When brake pedal (not shown in Figure) is depressed by the driver, the hydraulic fluid from the reservoir 113 is supplied via the primary port 119 to both the bleeding nipple 1 120 of the leading caliper of the two twin-pot brake calipers simultaneously with the supply of braking fluid to the rear drum brakes 111 & 112. A rear brake hose 110 supplies braking fluid to the rear drum brakes 111 & 112 through the LCRV 109 and by means of a rear braking pipe 108 connected to the primary port 119. The modified braking circuit 100A ensures that an additional one pot of the twin-pot brake calipers present in front disc brakes also applies braking along with the rear drum brakes, thereby achieving the required MFDD of Ml category of vehicles and preventing
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rear wheel locking. In addition to that, early rear wheel locking is also avoided without adding to the weight of the brake aggregates because of contribution of front tire utilization.
The braking circuit 100A with respect to another embodiment of the present invention comprises a primary port 119 connected to rear drum brakes 111 & 112 and bleeding nipples 2 121 of trailing calipers of the front twin-pot brake calipers.
The braking circuit 100A with respect to yet another embodiment of the present invention comprises a secondary port 118 connected to rear drum brakes 111 & 112 and bleeding nipples 2 121 of trailing calipers of the front twin-pot brake calipers.
It is reiterated that the present invention is not limited to the above embodiments. Various other embodiments of the invention will be apparent to a person skilled in the art or follow from routine experimentation.
Dated this 18th day of June, 2007

To
The Controller of Patents,
Patent Office, Mumbai
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