FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Isolator stuck indication arrangement
APPLICANTS
Mahindra & Mahindra Ltd., Gateway Building, Apollo Bunder, Mumbai 400 001, Maharashtra, India, an Indian company
INVENTORS
Chinnathambi Manikandan, 8, Koodalinga Nadar Street, Thiruthangal, Virudhunagar, 626130, Tamil Nadu, and P S Rajram, 12, 11th cross Street, Annanagar, Chengalpattu, Kanchipuram, 603001, Tamil Nadu, both Indian nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention generally relates to the vehicle run time display on the instrument cluster. Run time display on the instrument cluster helps decide the serviceability of the vehicle. More particularly, the present invention relates to a tamper proof logic for the calculation of the run time with a simple and low cost improvement.
BACKGROUND OF THE INVENTION
In automotive applications, especially in tractors, the run time of the tractor is used to decide the service due time. Usually a warranty period of 2 years is given as warranty for the tractor. During this period, any error with the instrument cluster will come under warranty claim. To calculate this time, tractor run hour is calculated based on the engine RPM (rotations per minute).
Earlier, 96000 rpm was considered as 1 hour. So if the engine rpm is 800, then exactly after 120 minutes (96000/800), 1 hour used to be incremented on the hour counter. But when the engine rpm is 2400, after 40 minutes (96000/2400) 1 hour will be incremented on the hour counter. So the logic had to be changed. A timer was used to count the run hour. Once the RPM signal was present, the hour meter used to start counting.
The only input that was considered for calculating run hour was the engine RPM. But if the customer cut the output from speed sensor to cluster, the hour meter would stop

counting. So the correct service time could not be calculated. The customer would make wrong claims based on this service time. So it was a loss to the company/ service.
The solution for this shortcoming has been specified in the present invention. The logic is based on a counter using three inputs to find the vehicle/ tractor run hour instead of just considering the RPM alone.
OBJECTIVES OF THE INVENTION
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
The main objective of the present invention is to provide a simple, cost effective tamper proof logic for finding run hour suitable for any type of automobile.
Yet another advantage is that this logic helps the driver to understand the correct run hour even if the RPM signal is corrupted.
SUMMARY OF THE INVENTION
The present invention relates to a system used in vehicles for indicating the run time of said vehicle, said system comprising of:
A. a counter to receive signals from (i) the engine speed sensor (RPM), (ii) the
pressure switch (EOP); and (iii) the charging circuit (SOP);
B. an LED driving circuit to receive said EOP and SOC, such that LEDs driven
by said LED driving circuit blink when input signal to EOP or SOC is high;

C. means to display vehicle run time; wherein said display means are connected to said counter;
such that said counter counts, when
a. ignition of said vehicle is ON and RPM is present; or
b. ignition of said vehicle is ON and RPM is not present and
i. LED for EOP is OFF and LED for SOP is OFF; or ii. LED for EOP is ON and LED for SOP is OFF; or iii. LED for EOP is OFF and LED for SOP is ON.
DETAILED DESCRIPTION OF THE INVENTION
The main objective of the present invention is to provide a simple, cost effective tamper proof logic for finding run hour suitable for any type of automobile. As a preferred embodiment, the present invention is explained with reference to a tractor. However, any vehicle can be used in place of a tractor.
3 inputs are given to a counter - engine RPM, battery state of charge and engine oil pressure.
RPM signal will be produced only when the ignition is on and the engine rotates, which gives an indication of the vehicle/ tractor run. So the RPM is chosen as one of the input signal and is given the main priority. If RPM signal present, tractor run time is calculated and incremented.
However, if the RPM wire is tampered, the hour meter will not count. Therefore, the present invention includes two more signals which indicate the tractor run.

Engine oil pressure (EOP) should build up to a certain value when the tractor is running. If it is low, then an indication is given on the cluster. This signal is also taken as the input to the counter.
State of charge (SOC) shows the charge level of battery. Once the tractor runs, the alternator charges the battery. But if the alternator does not charge the battery, the battery discharges. There is an indication on the cluster for the battery discharge stage. This signal will indicate whether the tractor is running or not. So this is also taken as an input to the counter.
The proposed invention states that hour meter should count only when any two of the three inputs to the counter is present.
The tamper proof logic is -
a) When IG is ON and RPM signal is present, hour meter should count.
b) When IG is ON and RPM signal not present, the status of SOC LED and EOP LED should be checked.
i. If EOP LED is OFF & SOC LED is OFF, hour meter should count, ii. If EOP LED is ON & SOC LED is OFF, hour meter should count, iii. If EOP LED is OFF & SOC LED is ON, hour meter should count, iv. If EOP LED is ON & SOC LED is ON, hour meter should not count.
c) When IG is OFF and RPM signal not present, hour meter should not count.
This logic will ensure that even if the RPM signal wire is tampered, the hour meter will count if the other two signals are present.

If the EOP wire is also tampered, then according to the present invention, SOC is checked. The connection to battery cannot be tampered because once that wire is cut, the battery will not be charged. So it should be replaced very often.
The above mentioned and other features and advantages of the various embodiments of the invention, and the manner of attaining them, will become more apparent and will be better understood by reference to the accompanying drawings, wherein:
Fig 1 illustrates the block diagram of instrument cluster.
Fig 2 illustrates the interfacing diagram of the vehicle inputs to the instrument cluster and the output from it.
Fig 1 illustrates the block diagram of the instrument cluster showing only the parts related to the present invention. Tacho input (1), coming from the engine speed sensor is given to the analog input signal conditioning block (2). The analog signal is conditioned in this block and given to the stepper motor driver (3). The RPM meter of the proposed cluster is stepper motor type. So the stepper motor driver is used to drive the stepper motor. The output is given to drive the RPM gauge (4) and the RPM is displayed on it. The input which is given to the stepper motor driver is also given to the counter (13) where the proposed invented logic is carried out. The EOP signal (6) coming from the pressure switch (not shown in the figure) is given to another input signal conditioning block (8) where the high/low signal conditioning is done. The digital output is given to the LED driving circuit (9) to drive the warning LEDs. The driving output signal is given

to the LED for EOP (10). The said LED will blink when the input to it is high. The digital output is also given to the counter (13) where the proposed invented logic is carried out. Similarly the SOC signal (7) coming from the charging circuit is given to input signal conditioning block (8), then to the LED driving circuit (9) for driving the warning LED for SOP (11). The LED will blink when the input to it is high. The digital output is also given to the counter (13) where the proposed invented logic is carried out.
The output from the counter, the tractor run hour is given to a LCD driver circuit (5) which drives the LCD Display (12).
The connection details of the instrument cluster of the present invention are described in Figure 2. The said figure shows only the connections valid to the present invention. Battery (22) is giving the supply to the cluster. The battery positive (14) is given to the ignition switch (16). When ignition is ON the switch 16 closes and supply is given to the CPU (20). Battery pin (15) is directly connected to the CPU so that when ignition is not there, the RPM value goes to zero without being stuck at the previous value. GND (17) is also given to the CPU (20) to complete the circuit. Speed sensor signal from Tacho input (1) is given to the CPU. After proper conditioning, the signal is given to Tachometer 4.
EOP signal (6) coming from the pressure switch is given to the CPU where high/low signal conditioning is done and the output is given to the warning LED (10). Similarly the SOC signal (7) coming from the charging circuit is given to the CPU (20) where high/low signal conditioning is done and the output is given to warning LED (11). The tractor run hour is displayed on LCD (6). Reset switch (19) is also provided to reset

the trip hour meter reading displayed on the LCD Display (6). The service due time is calculated from the service reminder acknowledgement (18) and input from the ignition switch (16). The warning signals is accompanied by a buzzer sound which is done by the buzzer circuit (21).
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.

, We claim:
1. A system used in vehicles for indicating the run time of said vehicle, said system
comprising of:
A. a counter to receive signals from (i) the engine speed sensor (RPM), (ii)
the pressure switch (EOP); and (iii) the charging circuit (SOP);
B. an LED driving circuit to receive said EOP and SOC, such that LEDs
driven by said LED driving circuit blink when input signal to EOP or SOC
is high;
C. means to display vehicle run time; wherein said display means are
connected to said counter-
such that said counter counts, when
c. ignition of said vehicle is ON and RPM is present; or
d. ignition of said vehicle is ON and RPM is not present and
i. LED for EOP is OFF and LED for SOP is OFF; or ii. LED for EOP is ON and LED for SOP is OFF; or iii. LED for EOP is OFF and LED for SOP is ON.
2. A system as claimed in Claim 1, wherein said counter stops counting when
a. ignition of said vehicle is ON and RPM is not present; and
i. LED for EOP is ON and LED for SOP is ON; or
b. ignition of said vehicle is OFF and RPM is not present.

3. A system as claimed in Claim 1 or 2, wherein said input signals to said counter undergo signal conditioning before being given to said counter.
4. A system as claimed in any of the Claims 1 to 3, further including reset means for resetting said display means.