Title of Invention

METHOD OF TESTING TYRE STRENGTH

Abstract

This invention relates to method of testing tyre strength, the said invention shall produce results which aids in assessing tyre strength in developmental stage, compare and judge against other brand tyres which are already in field. This invention help in field simulations with best co-relations for tyre load capacity profile and failure modes, Ranking with existing tyres and used as gauge for comparing tyre strengths, Reduction in development time and cost, Carry out early modifications and minimize field failures, select the best tyres from all brands considered. This invention helps in evaluating the ultimate tyre strength in terms of load carrying capacity in a precise manner and benchmark with brands with minimum test durations.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) AND THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE OF INVENTION Method Of Testing Tyre Strength 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 Mr. Gopalakrishna K. and Mr. N Prabhakar Swamy both 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 specification particularly describes the invention and the manner in which it is to be performed. FIELD OF INVENTION This invention relates to testing of tyres used in all applications with pneumatic tyres including Bias ply and Radial tyres with and without tubes and more particularly to the method of testing tyre strength. BACKGROUND OF INVENTION In the process of tyre developments for automobile applications, selection criteria are largely based on load carrying capabilities and speed ratings. The strength of a tyre is decided by the number of ply rating. Various brand tyres with same specifications exhibit large variations in performances in fields. Tyre development is a long process and involves various test and iterations-modifications. Tyre of same specification of various brands perform differently under similar usage conditions due to various design aspects, materials and composition used and manufacturing process quality. There could be some surprise failures from field based on customer usage pattern. Conventional Regulations and standards such as Economic Commission for Europe (ECE) R-54, Automotive Industrial Standard (AIS) 044, and Federal Motor Vehicle Safety Standard (FMVSS) 109, 110,119,120,139 are specified to evaluate the minimum performance required by these tyres. Vehicle manufactures always look for the best tyres out of all brands. This invention helps in selection of tyres based on the ranking of performance in terms of tyres strength. OBJECTS OF INVENTION The main object of the present invention is to provide the method of testing tyre strength Another object of the present invention is to provide the method of testing tyre strength, which is quick and simple. STATEMENT OF INVENTION Method of testing tyre strength comprises of - Selecting tyre of required size to be tested; - Setting the tyre pressure and speed at which the test is to be carried out; - Conditioning the said tyre for at least one hour; - Loading the said tyre on the test rig; - Running said tyre at pre determined speed with predetermined tyre pressure; - Recording the chamber ambient temperature and tyre temperature at different locations of tyre; - Subjecting the said tyre with incremental load for fixed durations until tyre failure occur at particular location; - Measuring the tyre temperature at said different location; - Recording the locations of said failure; - Calculating the total energy absorbed index; - Ranking the said calculated total energy absorbed index; - Carrying out modification if improvement is required; - repeating the above steps if modification or improvement is required; - selecting the best tyre. Method of testing tyre strength ,in accordance with this invention, wherein said different locations of tyres are crown, shoulder, side wall center, bead area close to rim of said tyre. Method of testing tyre strength, in accordance with this invention, wherein said step of subjecting the said tyre with incremental load comprises subjecting the said tyre with incremental load every half an hour. Method of testing tyre strength, in accordance with this invention, wherein tyre speed remains constant during the said incremental load application. Method of testing tyre strength, in accordance with this invention, wherein said step of ranking further comprises arranging the said total energy absorbed index calculated in ascending order. Method of testing tyre strength, in accordance with this invention, wherein said step of recording chamber ambient temperature comprises recording said chamber ambient temperature every 2 hrs for reference. Method of testing tyre strength, in accordance with this invention, wherein tyre temperature at all four locations is measured every 15 minute. Method of testing tyre strength, in accordance with this invention, wherein said step of modification comprises; Plotting recorded tyre temperature against load and time to analyze for stabilization, peak and failure, Carrying out modification in rubber and material composition if required. BRIEF DESCRIPTION OF INVENTION This invention shall produce results which aids in assessing tyre strength in developmental stage, compare and judge against other brand tyres which are already in the field. This invention helps in 1. Field simulations with best co-relations, for tyre load capacity profile and failure modes. 2. Ranking with existing tyres and used as gauge for comparing tyre strengths. 3. Reduction in development time and cost. 4. Carry out early modifications and minimize field failures. 5. Select the best tyres from all brands considered, Unlike regulatory and standard test, this invented procedure evaluates, breaking endurances strength, by subjecting tyres in incremental load for fixed durations until failures. Total energy observed is calculated and ranked in ascending order. Various brands of tyres are subjected to this test or can be benchmarked or compared against library results. Test can be conducted in a short span which facilitates quicker selection with regard to tyres strength, otherwise which would have taken a long lead time in field evaluations. SUMMARY OF INVENTION In accordance with this invention, Method of testing tyre strength comprises the step of - Selecting the tyre of required size to be tested, Fixing the tyre pressure and speed at predetermined level, - Conditioning the said tyre for at least one hour, - Loading the said tyre on the test rig, Recording the chamber ambient temperature and tyre temperature at all four location (crown, shoulder, side wall center, bead area close to rim) of tyre, - Subjecting the said tyre with incremental load for fixed durations until failures, - Measuring the tyre temperature at all four said locations, - Continuing the test until tyre failure, - Recording the location of said failure, - Taking photograph for reference, - Calculating the total energy absorbed index, - Ranking the said calculated total energy absorbed index, - Carrying out modification if improvement is required, - Repeating the above steps if modification or improvement is required, selecting the best tyre. Wherein said different location of tyres are crown, shoulder, side wall center, bead area close to rim of said tyre. Said step of subjecting the said tyre with incremental load comprises subjecting the said tyre with incremental load every half an hour. Wherein tyre speed remains constant during the said incremental load application. Said step of ranking further comprises arranging the said total energy absorbed calculated in ascending order. Said step of recording chamber ambient temperature comprises recording said chamber ambient temperature every 2 hrs for reference. Wherein tyre temperature at all four locations is measured every 15 minute. Wherein said step of modification comprises; - Plotting recorded tyre temperature against load and time to analyze for stabilization, peak and failure, - Carrying out modification in rubber and material composition if required. BRIEF DESCRIPTION OF DRAWING Fig. 1- shows a flow chart of the method of testing tyre strength in accordance with this invention. DETAILED DESCRIPTION OF INVENTION Referring to Fig. 1, tyre strength evaluation test is conducted in tyre test lab. Rig / equipment consist of roller drum with 1.7m diameter over which tyre is pressed under load. Load and Drum speeds as detailed in the procedure mentioned below. Cabin/chamber temperatures recorded every 2 hours before changing over to next load. Tyre temperature on various locations such as bead area, side wall, shoulder and crown are recorded continuously or at defined frequency i e every 15 minutes, test shall be stopped as soon as failure occurs or physical deformations of tyres are observed. A safety switch is to be provided on the test rig to avoid damage to roller drum and test rig. In accordance with this present invention, method of testing tyre strength comprises the step of - tyre of required size is selected, - the speed and pressure of said tyre is fixed at predetermined level. - said tyre is kept for conditioning for at least one hour. - said tyre is loaded on the test rig for conducting the said test. - the ambient temperature of cabin or chamber is recorded. - the temperature of said tyre at crown, shoulder, side wall center and bead area closed to rim is recorded. - said tyre is subjected with incremental load for fixed duration, generally for half an hour and again the load is increased and subjected for another half an hour. - said tyre is subjected with this kind of incremental load every half an hour and continued until failure occurs. During the incremental load, - the temperature of said tyre at all said locations are measured at fixed interval, - generally tyre temperature of said tyre at all locations are measured at every fifteen minutes. - the above said steps are continued until the tyre failure occurs. - the said location of tyre failures are recorded and marked. - the photographs of said locations of tyre failures are taken for reference. - the total energy absorbed index is calculated by as Energy absorbed as product of difference between final and initial load and total time taken to failure. - said calculated total energy absorbed index is ranked in ascending order. - result which is close to the 100% is kept on priority or top of ranking list and result which is far below from the 100% is kept at bottom on ranking list. - the modifications are carried out if improvements are required. - the above-mentioned steps are repeated if the modification or improvement is required. - tyre temperatures plotted against load and time, to be analyzed for stabilization, peak and failure, carry out modifications in rubber and material compositions if required. Based on the test result the best tyre of good strength is selected from the ranking list which is most close to the 100 % strength criteria. During the test the tyre speed and tyre pressure is kept constant during the said incremental load application. The cabin or chamber ambient temperature is recorded every two hour before every changing over to next load. Method of testing tyre strength comprises of - Selecting tyre of required size to be tested; - Setting the tyre pressure and speed at which the test is to be carried out; - Conditioning the said tyre for at least one hour; - Loading the said tyre on the test rig; - Running said tyre at pre determined speed with predetermined tyre pressure; - Recording the chamber ambient temperature and tyre temperature at different locations of tyre; - Subjecting the said tyre with incremental load for fixed durations until tyre failure occur at particular location; - Measuring the tyre temperature at said different location; - Recording the locations of said failure; - Calculating the total energy absorbed index; - Ranking the said calculated total energy absorbed index; - Carrying out modification if improvement is required; - Repeating the above steps if modification or improvement is required; - Selecting the best tyre. wherein said different location of tyres are crown, shoulder, side wall center, bead area close to rim of said tyre. Wherein said step of subjecting the said tyre with incremental load comprises subjecting the said tyre with incremental load every half an hour. Wherein said tyre speed and tyre pressure remains constant during the said incremental load application. Wherein said step of ranking further comprises arranging the said total energy absorbed index calculated in ascending order. Wherein said step of recording chamber ambient temperature comprises recording said chamber ambient temperature every 2 hrs for reference. Wherein said tyre temperature at all said four locations is measured every 15 minute. Wherein said step of modification comprises; - Plotting recorded tyre temperature against load and time to analyze for stabilization, peak and failure, - Carrying out modification in rubber and material composition if required. The said tyre is subjected to load for a fixed durations as given in following table. Endurance test: Failure by over loading:- Sr.No. Speed Tyre pressure Load Duration, hrs 1 70km/h 135 PSI 3500 kg. ½ 2 70km/h 135 PSI 3700 kg. ½ 3 70km/h 135 PSI 3900 kg. ½ 4 70km/h 135 PSI 4100 kg. ½ 5 70km/h 135 PSI 4300 kg. ½ 6 70km/h 135 PSI 4500 kg. ½ 7 70km/h 135 PSI 4700 kg. ½ 8 70km/h 135 PSI 4900 kg. ½ Test to be continued till tyre starts to fail The above table is an example for 10x20 and 10.00 R 20,16 PR ( Ply Rating) tyres. Tyre pressure for the selected tyre should be 135% of rated tyre pressure, speed selected should be 90% of rated maximum speed and initial load should be 115% of rated load. The incremental load should be of 200 kg after every half an hour. All standard measurements and additional measurements or observations as below to be reported. a) Cabin /Chamber Ambient temperature is recorded every 2 hour for reference. b) The temperature of said tyre at said locations (crown, shoulder, side wall center, bead area close to rim) are measured. The frequency of measuring the temperature of said tyre at said locations is every 15 minutes. c) The total time for failures is recorded in minutes. Total time for failures is time taken from start of test to the time when failure occurs. d) The pressure of said tyre before start of test, and whenever measurement possible during test is recorded. e) Record the type of failures that occurs is recorded. f) Photographs of locations of failures before and after tests are taken for reference. The failures of said tyre in form of burst or any physical deformations and abnormality occurred during test are considered as failure. All the failures during this test of tyre occur on the shoulder or crown area. Any failures such as side wall or bead failure shall be considered as least performances and insufficient strength. Modification to be carried out on tyres to improve the side wall strength and re-tested for failure in crown and shoulder area. Energy observed in Joules to be calculated as product of breaking load and total time taken to failures. Results to be benchmarked with tyres of similar specifications and ranked accordingly as mentioned. Repeatability, accuracy of results is fairly achieved as the tyres and test conditions are same and similar for particular type of tyres. Tyre is inflated to higher inflation pressure is to accelerate the test process, as the temperatures raised at steady rate and influences the tyre performance in controlled manner. Increase in load at the steps evaluates failure loading capacities of tyres. Controlled time durations brings uniformity in testing process helps in stabilizing temperatures. 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. WE CLAIM 1. Method of testing tyre strength comprises of - Selecting tyre of required size to be tested; - Setting the tyre pressure and speed at which the test is to be carried out; - Conditioning the said tyre for at least one hour; - Loading the said tyre on the test rig; - Running said tyre at pre determined speed with predetermined tyre pressure; - Recording the chamber ambient temperature and tyre temperature at different locations of tyre; - Subjecting the said tyre with incremental load for fixed durations until tyre failure occur at particular location; - Measuring the tyre temperature at said different location; - Recording the locations of said failure; - Calculating the total energy absorbed index; - Ranking the said calculated total energy absorbed index; -Carrying out modification if improvement is required; - Repeating the above steps if modification or improvement is required; - Selecting the best tyre. 2. Method of testing tyre strength as claimed in claim 1, wherein said different location of tyres are crown, shoulder, side wall center, bead area close to rim of said tyre. 3. Method of testing tyre strength as claimed in claim 1, wherein said step of subjecting the said tyre with incremental load comprises subjecting the said tyre with incremental load every half an hour. 4. Method of testing tyre strength as claimed in claim 1, wherein tyre speed remains constant during the said incremental load application. 5. Method of testing tyre strength as claimed in claim 1, wherein said step of ranking further comprises arranging the said total energy absorbed index calculated in ascending order. 6. Method of testing tyre strength as claimed in claim 1, wherein said step of recording chamber ambient temperature comprises recording said chamber ambient temperature every 2 hrs for reference. 7. Method of testing tyre strength as claimed in claim 1, wherein tyre temperature at all four locations is measured every 15 minute. 8. Method of testing tyre strength as claimed in claim 1, wherein said step of modification comprises; - Plotting recorded tyre temperature against load and time to analyze for stabilization, peak and failure, - Carrying out modification in rubber and material composition if required. 9. Method of testing tyre strength substantially as herein described with reference to the accompanying drawings and complete specification. ABSTRACT Method Of Testing Tyre Strength This invention relates to method of testing tyre strength, the said invention shall produce results which aids in assessing tyre strength in developmental stage, compare and judge against other brand tyres which are already in field. This invention help in field simulations with best co-relations for tyre load capacity profile and failure modes, Ranking with existing tyres and used as gauge for comparing tyre strengths, Reduction in development time and cost , Carry out early modifications and minimize field failures, select the best tyres from all brands considered. This invention helps in evaluating the ultimate tyre strength in terms of load carrying capacity in a precise manner and benchmark with other brands with minimum test durations. Fig. l

Documents:

654-mum-2008-abstract.doc

654-mum-2008-abstract.pdf

654-MUM-2008-CLAIMS(AMENDED)-(15-2-2013).pdf

654-MUM-2008-CLAIMS(AMENDED)-(26-3-2014).pdf

654-MUM-2008-CLAIMS(MARKED COPY)-(15-2-2013).pdf

654-mum-2008-claims.doc

654-mum-2008-claims.pdf

654-mum-2008-correspondence(23-4-2008).pdf

654-mum-2008-correspondence-received.pdf

654-mum-2008-description (complete).pdf

654-mum-2008-drawings.pdf

654-MUM-2008-FORM 13(26-3-2014).pdf

654-mum-2008-form 18(23-4-2008).pdf

654-mum-2008-form 2(title page)-(26-3-2008).pdf

654-mum-2008-form 8(23-4-2008).pdf

654-mum-2008-form 9(23-4-2008).pdf

654-mum-2008-form-1.pdf

654-mum-2008-form-2.doc

654-mum-2008-form-2.pdf

654-mum-2008-form-26.pdf

654-mum-2008-form-3.pdf

654-MUM-2008-GENERAL POWER OF ATTORNEY(15-2-2013).pdf

654-MUM-2008-REPLY TO EXAMINATION REPORT(15-2-2013).pdf

654-MUM-2008-REPLY TO HEARING(26-3-2014).pdf

654-MUM-2008-SPECIFICATION(AMENDED)-(26-3-2014).pdf

654-MUM-2008-SPECIFICATION(MARKED COPY)-(26-3-2014).pdf

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