FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION
IMPROVED GEAR SHIFTING MECHANISM FOR AUTOMATIC TRANSMISSION OF A VEHICLE
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
Anand Swichalappa Damami, Amit Suhas Barve,
Prafulla Vijay Wankhede 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 provisional specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to the gear shifting mechanism of a vehicle & more particularly to gear shifting mechanism for automatic transmission of vehicle.
BACKGROUND OF INVENTION
In automatic transmission where two pulley sets are used to vary ratio also known as CVT. The Basic CVT comprises of two sets of pulley called as Driving pulley and Driven Pulley. The driving pulley is mounted on the Crankshaft of the Engine. The driven pulley is mounted on a Gearbox which can have following three modes, Neutral, Forward and Reverse. A belt is used to transfer power from Driving Pulley to Driven Pulley. This system does not contain external clutch.
At a particular set Engine rpm, the driving pulley with the help flyweights pinches the belt, thereby transmitting power to Driven pulley. This in turn rotates the Gears inside the Gearbox. Any attempt to change the mode of the gearbox when the driven pulley is rotating leads to Gear crashing. This also leads to damage of the Gears and gives an uncomfortable feeling to the occupant. Sudden engagement of gears during rotation of Gears may lead to abrupt motion of Vehicle which may be result in fatal accidents to the occupants inside or people outside the Vehicle.
To ensure that the gears are not engaged during their rotation a mechanism is required which ensures that the occupant does not increase the rpm of driving
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pulley. It is also important to ensure that the brakes are engaged during shifting of the mode.
To ensure safety of the occupants and the people on a vehicle with automatic transmission, where there is no separate clutching element, a mechanism is required so that the occupant cannot shift the gear lever until the brake pedal is pressed. This is to ensure that the occupant is not able to press the acceleration pedal during shifting of the Gear. The gear engagement is clash free. Also it won't allow the vehicle to move or crawl without leaving the brake pedal.
The high end gear shifting unit on an Automatic Transmission consists of a lever, enclosure, electric sensors and actuators. The electric signal from brake pedal is used as an input to the electric signal to an actuator. When the lever is in Park position, the said actuator, releases the lock only if brake pedal is pressed, so the lever position can be changed in the Gear shifting unit. The changed position of Lever enables the person / driver to select desired / intention mode.
The lever can be moved only if the Brake pedal activates the actuator situated in the Gear shifting unit. This ensures that the Vehicle does not move or creep, until the brake is released and safety of the occupants inside the vehicle and people outside the vehicle is ensured.
The above feature is achieved by electric/electronic sensor and actuators which are costly. Also it requires battery backup & malfunctioning of electrical / electronic circuit will affect the performance.
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OBJECTS OF INVENTION
The main object of this invention is to provide gear shifting mechanism with provision of changing the drive mode only when the brake pedal is pressed.
Yet another object of this invention is to provide a linkage mechanism which is simple in construction and cost effective.
DETAIL CONSTRUCTION OF THE INVENTION
The improved gear shifting mechanism for automatic transmission consists of interlock mechanism provided on gear shifter unit.
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,
Figure No 1 - Shows the layout of gear shifter mechanism with brake pedal.
Figure No 2 - Shows the gear shifter mechanism in accordance with this
invention.
Figure No 3 - Shows the two positions of the Brake pedal.
Figure No 4 - Shows the positions of the Gear lever for different modes
Figure No 5, 6, 7 & 8 - Shows the working of the system.
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As shown in the Figure 1 one cable (2) is connected from the brake pedal (1) to gear shifter unit (3) which in particular connected to the interlock mechanism.
As shown in Fig No 2, the interlock mechanism consist of interlock cam (5) which fits into two channels (7) which can move to & fro along channels. The interlock cam has grooves to hold the gear lever. Channels (7) are integral with gear shifter unit. One bell crank lever (6) is pivoted with pivot pin (4) which is anchored on anchoring bracket (9).The cable from brake pedal is connected to small link of the bell crank lever & another cam pulling pin(8) fixed to longer link. The cam pulling pin gets inserted into elliptical slot of interlock cam.
DETAIL FUNCTION OF THE INVENTION
Now with reference to Figure No 3 and 4, the system has brake pedal (1) which moves in two positions (la) and (lb).As the pedal moves from position (la) to (lb) the cable is pulled which in turns rotates the bell crank lever (6) about its pivot pin (4). The rotation of bell crank moves the interlock cam (5) in transverse direction.
The gear lever (3) has three positions namely (3a), (3b) and (3c). The (3b) position is for neutral (3a) for reverse and (3c) for Forward respective modes of the Gearbox.
When the pedal is pressed i.e. position of pedal is changed from (la) to (lb), the cable fixed to the pedal rotates the bell crank (6) which in turn moves the
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interlock (5). The movement of interlock enables the lever to be unlocked & moved either in Reverse (3a) or in Forward (3c) mode condition. After the lever is moved in either of the mode and movement of pedal back to (la) position ensures that the lever (3) is locked in either Reverse (3a) or forward (3c) mode. The interlock is held in the position with the help of the force generated with the help of spring either at the bell crank lever (6) or at the interlock cam (5)
This ensures that to shift the position of lever (3) movement of pedal from (la) to (lb) is required. The pedal is a brake pedal on an Automobile. This ensures that in order to shift the lever (3) from its current position the vehicle is automatically brought to stand still condition.
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 in so far as they come within the scope of the invention as claimed or the equivalents thereof.
Dated this 29th day of March 2007

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