FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION IMPROVED CLUTCH LINKAGE MECHANISM
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
Mohan Vinayak Kher, Janardhanan Venkatapathi,
Damodar Nageshwarrao Chollangi,. 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 provisional specification particularly describes the invention and the manner
in which it is to be performed.

Field of invention
This invention relates to an automotive hydraulic and mechanical clutch actuation system.
Background of the invention
The conventional clutch in an automobile consists of a clutch disc, cover assembly, release bearing and release mechanism. The clutch disc is a friction element which is clamped against the engine flywheel through the cover assembly. The said cover assembly sandwiches the clutch disc between the flywheel and the pressure plate and transmits the engine power to the gearbox.
The clutch engages / disengages only after a minimum amount of movement of the clutch release bearing. This movement of the clutch release bearing is achieved by the clutch linkage mechanism. The clutch linkage involves the clutch pedal unit and the linkages.
In particular, case of cable actuated clutch release mechanism is considered. In a cable type clutch linkage mechanism the clutch cable is attached to one end of the clutch pedal and the other end is to the clutch release lever. The clutch release lever has the clutch cable on one end and other end is mounted on a cross shaft, which has a clutch release yoke rigidly mounted on it. Movement of the yoke results in movement of the clutch release bearing.
In a conventional automobile, the clutch is disengaged when the clutch pedal is pressed and is engaged when the pedal is released. During gradual clutch pedal release the clutch smoothly engages and the vehicle starts moving. The engagement of the clutch is desired generally half way through the clutch pedal release for better manipulation of the clutch. It is also desired that the pedal effort requirements are met.
On any vehicle under consideration, the clutch engagement can be considered as late if the engagement takes place at a higher proportion of pedal travel from disengaged position. This
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late engagement feel is not preferred as the available travel for clutch manipulation is not sufficient, leading to discomfort to the driver.
The late engagement problem can be addressed by changes in the clutch or changes in the clutch linkage mechanism. Any change in the clutch viz. the cover assembly diaphragm characteristics is a costly and time consuming affair. The other approach is to redesign the clutch linkage mechanism, which has constraints of pedal travel and pedal effort requirements.
The present invention solves this problem of late clutch engagement in a cost effective way without reducing the pedal effort and pedal travel and minimum changes to the linkage mechanism.
Objects of this invention
1. The main object of this invention is to provide a clutch linkage mechanism which takes care of the minimum pedal effort requirement and pedal travel for an easy and sure manipulation of clutch.
2. Yet another object of this invention is to provide a clutch linkage mechanism which is simple in construction and cost effective.
Brief description of the invention
A cable type clutch linkage mechanism comprises of clutch release lever, release lever pivot pin, clutch cable, lock nuts along with the clutch pedal, wherein, the cable is connected to one end of the clutch pedal and the other end passes through the pivot pin in the clutch release lever. A_spring mechanism is inserted in the clutch release lever at the cable end, which absorbs a portion of the pedal travel thus changing the engagement / dis-engagement point of clutch. The said spring can be either helical spring or diaphragm spring. The other end of the clutch release lever is mounted on the clutch cross shaft which has the clutch release yoke welded on it. The clutch release yoke presses against the clutch release bearing, hence, when
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the clutch pedal is pressed the cable pulls the clutch release lever which in turn moves the clutch release bearing through the yoke and disengages the clutch.
The effective outcome is that the clutch release lever and bearing do not move for the initial pedal travel, till the helical spring at the release lever location gets fully compressed and any further pedal travel will move the release bearing in direct proportion to the pedal travel.
Detail description of invention
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 1 ~ Shows the clutch release lever arrangement with the pivot pin
Figure 2 - Shows the improved clutch linkage mechanism at the clutch pedal free condition
Figure 3 - Shows the improved clutch linkage mechanism with the clutch pedal pressed
condition
Figure 4 - Shows a layout of cable type clutch linkage mechanism.
Now with reference to figure 1, 2, 3 and 4, the clutch linkage mechanism has pivot pin (3) in the clutch release lever (1) at the cable end. The release lever pivot pin (3) has a hole perpendicular to its pivot axis. In this hole is located the guide sleeve (4) made up of metallic materials such as steel, aluminium, bronze, etc. and non-metallic such as plastic, teflon, etc.. The helical compression spring (5) is inserted on the guide sleeve(4) and locked with the help of hexagon nut (7) or circlip or a snap ring. The clutch cable (2) passes through the guide sleeve (4).
The assembled length of the helical spring (5) depends on the required position of the clutch engagement point. The spring (5) also balances the weight of the clutch pedal (9) and has sufficient stiffness so that it does not interfere with the clutch diaphragm spring characteristics.
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When the clutch pedal (9) is pressed, the cable (2) pulls the guide sleeve (4) through the Cable nuts (8). The lock nut (7) on the guide sleeve in turn compresses the helical compression spring (5) against the pivot pin (3) till the spring (5) becomes solid. The guide sleeve (4) slides in the pivot pin (3). This travel of the clutch pedal required to compress the helical spring (5) from assembled to full compressed length does not result in any movement of the release lever (1). The further clutch pedal travel will result in the movement of the clutch release lever (1) With this arrangement, the clutch release lever (1) movement is zero til! the helical spring is compressed fully and later the clutch release lever (1) moves in direct proportion to the pedal travel movement. This delayed clutch release bearing movement moves the clutch engagement point nearer to the pedal pressed condition making it ergonomical. This mechanism does not increase the peak pedal effort. This mechanism also does not affect the adjustment / arrangement for clutch wear compensation.
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 insofar as they come within the scope of the invention as claimed or the equivalents thereof.
Dated this 5th day of February 2007
TATA MOTORS LIMITED By their Agent and Attorney
(KARLTNA GOLERIA) of DePENNING & DePENNING
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Abstract
Title: IMPROVED CLUTCH LINKAGE MECHANISM
This invention relates to the improved clutch linkage mechanism comprising of clutch release lever, release lever pivot pin, clutch cable, lock nuts along with the clutch pedal, wherein the cable is connected to one end of the clutch pedal and the other end passes through the pivot pin in the clutch release lever. A spring mechanism is inserted in the clutch release lever at the cable end, which absorbs a portion of the pedal travel thus changing the engagement / disengagement point of clutch. The other end of the clutch release lever is mounted on the clutch cross shaft which has the clutch release yoke welded on it. The clutch release yoke presses against the clutch release bearing, hence, when the clutch pedal is pressed the cable pulls the clutch release lever which in turn moves the clutch release bearing through the yoke and disengages the clutch. With this arrangement, the clutch release lever movement is zero till the helical spring is compressed fully and later the clutch release lever moves in direct proportion to the pedal travel movement