FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
CLUTCH WEAR INDICATOR FOR VEHICLES SUCH AS TRACTORS AND ALIKE
2. APPLICANT(S)
MAHINDRA & MAHINDRA LIMITED.
GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001, MAHARASHTRA, INDIAN.
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
The present invention generally relates to a clutch wear indicator for use with off road vehicles such as tractors and alike, wherein the clutch wear indicator is disposed at the outside of the clutch housing and at the exposed area of the vehicle thereby to facilitate operator/mechanic to visually realize remaining useful life of the clutch plate.
BACKGROUND OF THE INVENTION:
Clutches are generally used in motor vehicles such as off road vehicles such as tractors and on road vehicles, as torque transmitters and as slip clutches at high spike load conditions. Excessive wear of friction lining of the clutch plate and lack of timely identification of the need to service/ replace the same, mainly due to non indication of the extent of its wear has rendered tractors immovable during field applications and is a major irritant to the customer. Hence for maintenance purposes, the service technician or driver shall be able to quickly and easily determine the extent to which the clutch is worn even in conditions where clear and unobstructed visibility is difficult. In particular, the operator/mechanic shall be conveniently able to determine if the clutch plate is worn to the point where it should be replaced.
Many modern motor car vehicles are equipped with warning systems indicating the driver of low essential liquid level (coolant, fuel, oil etc),

neutral switch etc. but satisfactory clutch wear life indicator is not developed.
Existing systems either involve sensors to determine the extent of friction lining wear or involve large number of additional parts in the clutch housing and release system. Both the methods are expensive and not suitable for tractors targeting the bed rock farmer segment.
US Patent 2425985 involves a circuit breaker which is normally held open by the position of the clutch plates and produces a warning signal as the clearance in the clutch release mechanism is closed. US Patent 3982614 also involves an electrical circuit to produce a warning signal at the clutch maximum wear limit. These electrical systems are expensive and may not be reliable for off road application all the time.
US Patent 5908907 describes a mechanical warning system suitable for hydraulically actuated release mechanism.
Hence an innovative and cost effective method of clutch wear indicator has been developed that does not require large number of changes in clutch housing and release mechanism which is actuated by a mechanical linkage.
The clutch wear indicator described herein is an indicator element, which is coupled to the release shaft from the outside of the housing enclosing the friction clutch, to which the release fork is attached.

Calibration is provided in the clutch housing indicating the different extent/ level of wear of the friction clutch. The indicator element rotates on the calibrated area in the clutch housing indicating the magnitude of wear of the friction clutch. The magnitude of the movement of the indicator element directly indicates the extent of wear.
SUMMARY OF THE INVENTION:
The present invention overcomes the shortcomings associated with the prior art and achieves other advantages not realized by the background.
The main objective of the present invention is to provide a clutch wear indicator specifically adapted to use with off road vehicles such as tractors, wherein life of clutch plate is visually recognizable by disposing a calibrated angular scale and a pointer at the outside of the clutch housing at the exposed area of the vehicle.
Another objective of the invention is to develop a clutch wear indicator which is very simple in design with less complexity in parts, assembly and maintenance.
According to the present invention, one aspect of the clutch wear indicator comprises a pointer and an angular calibration engraved on surface of wall of the clutch housing. The pointer is having a first end made as pointed

shape to precisely indicate corresponding reading in the angular calibration and a second end is adapted to rigidly connect with the projected end of the shaft. The angular calibration has a reading ranging from 0° to 15° wherein each unit is marked in the calibration measures 1°. This 15° angular distance corresponds to the maximum travel of the clutch release sleeve backward due to the wear happening during the lifetime of the clutch plate. In the present invention, linear backward movement of the clutch release sleeve is converted into angular movement of the pointer in clockwise direction at outer of the clutch housing for visually realizing the life of the clutch plate, and thereby defining a limit to the extent wear of the clutch plate may be afforded/acceptable for effective functioning thereof and further identify need to service or replace the same.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description with reference to the annexed drawings wherein:
FIG.l is a longitudinal sectional view of clutch housing enclosing clutch assembly incorporated with a clutch wear indicator according to the present invention.

FIG.2 is a cross sectional view taken along line AA of FIG.l.
FIG.3 is an elevation of FIG.l incorporated with the clutch wear indicator according to the present invention.
FIG.4 is an elevation of FIG.l showing complete assembly of the present invention in the vehicle.
DETAILED DESCRIPTION OF THE INVENTION
While this invention is susceptible of embodiments in many different forms, the detailed description of the preferred embodiments and the corresponding drawings shown herein below are to be understood that the present disclosure shall be deemed as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of FIG. 1- 4.
Referring to FIG.l, the clutch housing incorporating the clutch wear indicator according to the present invention is designated as 100. A typical clutch housing 100 encloses a flywheel 101 which is a part of engine output power to transmission, a clutch assembly 102 mounted on to the flywheel 101 for engaging and disengaging the power between the engine and the transmission, a clutch actuation mechanism 103 and a main shaft 104 to drive the power from the clutch assembly 102 to the transmission.

The clutch assembly 102 comprises a clutch plate 105 adapted to abut with the flywheel wherein friction face of inner surface of the clutch plate 105 (towards the flywheel) is mate with outer surface of the flywheel 101 (facing towards the clutch plate) and a pressure plate 106 is pushed over the clutch plate 105 axially from outer end of the clutch assembly 102 wherein friction face of outer surface of the clutch plate 105 is mate with the inner face of the pressure plate 106. Said clutch plate 105 and the pressure plate 106 are enclosed in a clutch cover 107 that is rigidly mounted over the flywheel thereby to transfer the power from the engine to the transmission via the main shaft 104 as a single unit.
The clutch assembly 102 also comprises a diaphragm spring 108 pivotally connected with the clutch cover 107 and having an outer radial end abut with axial projection extended from outer surface of the pressure plate and an inner radial end being adapted to design such that to operatively abut with the clutch actuation mechanism 103. It is to be understood from the aforementioned disclosure that the present invention is intended to work with any type of clutch irrespective of its construction. Illustration of the diaphragm type clutch is specifically described not to limit scope of our present invention, rather for supporting and reasoning the conception of this invention.
The clutch actuation mechanism 103 comprises a clutch release sleeve 109 which is inserted and guided over a guide tube 110 that is rigidly mounted

to the clutch housing lateral wall 111 coaxial with central axis of the clutch assembly 102. The main shaft 104 is inserted through the guide tube 110 and engaged with the clutch assembly via spline provided at inner end of the main shaft 104. Disposed there at inner end of the of the clutch release sleeve 109 is a release bearing 112 which is adapted to abut with the inner radial end of the diaphragm spring 108. The clutch actuation mechanism 103 further comprises a fork 113 that is rigidly supported on to a shaft 114 for relatively and axially moving the clutch release sleeve 109 towards the clutch housing assembly 102 so as to push the inner radial end of the diaphragm spring 108 to disengage the clutch plate 105 from the flywheel 101. The shaft 114 is inserted through the clutch housing 100 laterally via bushes each at the two walls of the clutch housing 100 and an end 114a facing clutch pedal location is projected outside of the clutch housing 100. The fork has a pair of finger 113a adapted to pivotally connect with the clutch release sleeve 109 at its outer end via a pin 115.
Referring to FIG.2, a linkage mechanism 116 is described in detail to illustrate as to how the clutch actuation mechanism 103 is operated from the outside of the clutch housing 100 at operator end. The linkage mechanism 116 comprises a link 117 endowed with an adjusting means 118 to adjust length thereof between a predefined upper limit and lower limit. The adjustment means 118 includes a nut and threading arrangement which enable the operator to set the length of the link 117 thereby to adjust

effectiveness of the clutch as while the clutch plate is getting worn out as the vehicle run for years. Provided at a first end and a second end of the link 117 is a yoke 119, wherein the yoke at the first end is pivotally coupled with a first end of an elongated bar 120 and the yoke at the second end is pivotally coupled with a mounting sleeve 121 of a clutch pedal (not shown). Wherein, a second end of the elongated bar 120 is rigidly connected with outer projected end 114a of the shaft 114. Profile of the elongated bar 120 is being adapted to operably connect between the projected end 114a of the shaft 114 and the second end of the link 117.
The present invention on clutch wear indicator incorporated with aforesaid construction is described in detail herein below with reference to FIG.2 & FIG.3. According to the present invention, a clutch wear indicator 122 comprises a pointer 123 and an angular calibration 124 engraved on surface of wall of the clutch housing 100 (it is understandable that this angular calibration can be engraved on some separate part like a plate which can be fixed on to the clutch housing 100). The pointer is having a first end made as of pointed shape to precisely indicate corresponding reading in the angular calibration 124, and a second end is adapted to rigidly connect with the projected end 114a of the shaft 114. It is understandable that an ordinary person can design a pointer of different shape or profile as one wishes without departing from the scope of the present invention and illustration of the pointer described herein should be construed as an

exemplary. According to the present invention, the angular calibration 124 has a reading ranging from 0° to 15° wherein each unit marked in the angular calibration measures 1°. (Again, it is understandable that various different scales as desirable / suitable for the application can be considered.) This 15° angular distance corresponds to the maximum travel of the clutch release sleeve 109 backward due to the wear happening during the lifetime of the clutch plate. In the present invention, linear backward movement of the clutch release sleeve 109 is converted into angular movement of the pointer 123 in clockwise direction at outer of the clutch housing 100 for visually realizing the life of the clutch plate 105, and thereby defining a limit up to which wear of the clutch plate 105 may be afforded/accepted for effective functioning thereof.
In this typical construction of clutch assembly 102, clutch actuation mechanism 103 and linkage mechanism 116, the adjustment of the gap between the inner radial end of diaphragm spring 108 and the release bearing 112, and effectiveness of the clutch in engaging and disengaging the power is done by the operator/mechanic by adjusting the length of the link 117 via adjusting means 118. By threading the nut, the length of the link shall be adjusted. During the initial setting, length of the link 117 is set at its maximum length or as specified by the setting of the clutch assembly 102 as shown in FIG.4. As time passes on during the life time of the vehicle, the clutch plate 105 keeps getting worn out and as a consequence

of that the inner radial end of the diaphragm moves outward and tends to abut with the release bearing 112. This may further lead to push the clutch release sleeve 109 backward and affect reliability of the clutch assembly 102 thereby adversely affect the operator comfort. Hence, to obviate these problems, it is advised that sufficient gap be maintained between the inner radial end of the diaphragm spring 108 and the release bearing 112. In conventional clutch assembly, minimum 3 mm gap needs to be maintained all the time.
Generally this gap is adjusted by reducing the length of the link 117. Referring to the FIG.4, as the length of the link 117 reduces, the elongated bar 120 rotates in clockwise direction to the extent of the reduction of the length of the link 117. Thus the clockwise rotation of the elongated bar 120 makes the fork 113 to rotate in clockwise in the same proportion and thereby push the clutch release sleeve 109 backward and maintain appropriate/ comfortable gap for the effective functioning of the clutch assembly. Prior to this present invention, the operator/mechanic would set the gap based on his/her experience which is highly person-based and may not be perfect/ good enough all the time. But, according to the present invention, as the elongated bar 120 rotates in clockwise direction, the pointer 123 also moves in the clockwise direction in the same proportion and shows the exact reading in the angular calibration 124 within the selected range of 0° to 15°. This visual indication of reading in the angular

calibration 124 and a red mark representing 90% of the total clutch life present therein makes the operator/mechanic realize the life of the clutch plate and thereby to take appropriate decision (towards any service/ replacement need)conveniently without any ambiguity about the effective function of the clutch plate 105.

We claim:
1) A clutch wear indicator for use with off road vehicles such as tractors comprising:
a clutch housing (100) for enclosing a flywheel (101) and a clutch assembly (102), wherein the clutch assembly (102) is mounted on to the flywheel (101) for facilitating engagement and disengagement of engine power between engine and transmission, and comprises a clutch plate (105) adapted to abut with the flywheel (101) and a pressure plate (106) to push the clutch plate (105) axially from outer end of the clutch assembly (102), wherein the clutch plate (105) and the pressure plate (106) are enclosed in a clutch cover (107) that is rigidly mounted over the flywheel, said clutch assembly (102) also comprises a diaphragm spring (108) pivotally connected with the clutch cover;
a clutch actuation mechanism (103) having a clutch release sleeve (109) inserted and guided over a guide tube (110) which in turn rigidly disposed with the clutch housing (100), a release bearing is disposed at inner end of the of the clutch release sleeve (109) adapted to abut with inner radial end of the diaphragm spring (108), said clutch actuation mechanism (103) further comprises a fork (113) that is rigidly supported on to a shaft (114) for relatively and axially moving

the clutch release sleeve (109) towards the clutch housing assembly (102) so as to push inner radial end of the diaphragm spring (108) to disengage the clutch plate (105) from the flywheel (101);
a linkage mechanism (116) includes a link (117) endowed with an adjusting means (118) to adjust length thereof between a predefined upper limit and lower limit, the adjustment means (118) includes a nut and threading arrangement to enable operator to set length of the link (117) thereby to adjust effectiveness of the clutch as the clutch plate is getting worn out over the years, first end of the link (117) is pivotally coupled a first end of an elongated bar (120) and second end is pivotally coupled with a mounting sleeve (121) of a clutch pedal, second end of the elongated bar (120) is rigidly connected with outer projected end (114a) of the shaft (114); characterized in that
a clutch wear indicating means (122) comprises a pointer (123) and a calibration (124) disposed on outer surface of the clutch housing (100), the pointer (123) is adapted to move over the calibration and having a pointed first end to precisely and accurately indicate corresponding reading in the calibration (124) and a second end adapted to rigidly connect with the projected end (114a) of the shaft (114), the calibration (124) has a reading scale ranging from a lower limit and an upper limit in accordance with the extent to which axial adjustment of the clutch release sleeve (109) is done due to the wear

of the clutch plate (105) over a period of time (useful life of the clutch plate).
2) The clutch wear indicator according to claim 1, wherein the calibration is an angular calibration.
3) The clutch wear indicator according to claim 2, wherein reading in the angular calibration ranges from 0° to 15°.
4) The clutch wear indicator according to claim 3, each unit in the angular calibration reads 1°.