Claims:WE CLAIM:
1. An improved design of vulcanised rubber strip (100) for use in a retreading process of motor vehicle tires, comprising of:
a vulcanised tread rubber positioned to a tread area (20) of a tire casing (10);
wherein the vulcanised tread rubber has a pair of circumferentially continuous annular grooves (30, 40) which divide the vulcanised tread rubber into multiple tread portions comprising a center crown portion (50) and a pair of shoulder portions (60, 70);
characterized in that, the center crown portion (50) of vulcanised tread rubber is made of abrasion resistant polymer material and carbon black (CB) with lower particle size and higher structure, Wherein the pair of shoulder portions (60, 70) of vulcanised tread rubber is made of low abrasion resistant diluent material; carbon black (CB) and mineral fillers having less resistance to abrasive forces;
wherein the center crown portion (50) and the pair of shoulder portions (60, 70) represent at 20 – 80 % of vulcanized tread rubber.
2. The improved design of vulcanised rubber strip (100) for use in a retreading process as claimed in claim 1, wherein the design of vulcanised rubber strip using a pre-cure retreading process comprising the steps of:
removing damaged or existing tread rubber from a tire casing;
preparing a surface of the tire casing;
applying a thin layer of uncured gum to the surface of the prepared tire casing;
applying new pre-cured tread rubber over the uncured gum, wherein the pre-cured tread rubber is a long, flat strip of the tread rubber into which has been molded or cured of the finished tread i.e. grooves, lugs, tread elements, sipes, and etc.;
wrapping circumferentially the tread rubber around the surface of tire casing; and
trimming and butt-splicing ends of the tread rubber together.

3. The improved design of vulcanised rubber strip (100) for use in a retreading process as claimed in claim 1, wherein the high levels of abrasion resistant polymer materials consisting of polybutadiene.

4. The improved design of vulcanised rubber strip (100) using a retreading process as claimed in claim 1, wherein the cost effective diluent materials consisting of rubber reclaims, rubber crumbs and carbon blacks (CBs) with suitable particle size and structures.

5. The improved design of vulcanised rubber strip (100) using a retreading process as claimed in claim 1, wherein the formulated rubber compounds are provided to impart the lower rolling resistance (RR) or lower tand at 60°C or lower hysteresis.

Dated this 23rd day of March, 2020

, Description:IMPROVED DESIGN OF VULCANISED RUBBER STRIP FOR USE IN RETREADING PROCESS
FIELD OF INVENTION
The present invention relates to the field of tire retreading, more particularly to this invention relates to an improved design of vulcanised rubber strip which is used for retreading worn tire in retreading process for motor vehicle tires.
BACKGROUND OF INVENTION
In general, retread technologies are divided into two categories – mold cure and pre-cure retreading system. Each retreading system has unique advantages but both systems produce equally effective retreaded tires for vehicles.
Mold-cure process: The mold-cure process involves removing as much rubber as from a worn tyre casing using a buffing machine with specified profile, from both the tire crown area and sidewall portions, and then applying new unvulcanized rubber strip to these surfaces. Then, the tyre is placed in a mold in curing process with specified time, temperature and pressure, and cured much as new tires are cured.
Pre-cure retreading process: The pre-cure process involves removing the old tread rubber from only the crown area of the worn tyre casing using a buffing machine with specified profile with specified radius and after specified profile buffing a thin layer of unvulcanized bonding gum rubber is then applied to the surface of this prepared crown area and new pre-cured tread material is applied over the uncured gum rubber. The pre-cured tread is a long, flat vulcanised strip of tread rubber into which tread pattern has already been molded, or cured, having all the features of the finished tread, i.e. grooves, lugs, tread elements, sipes, etc. This tread strip is wrapped circumferentially around the outer surface of the gum rubber layer and the ends of the tread strip are trimmed and butt-spliced together.
Accordingly, in the pre-cured tread process, vacuum is applied through a valve to the inside of outer curing envelope. This, in effect, causes the envelope to create the inward force around the exterior of the pre-cured tread, compressing it against the gum rubber and carcass of the tyre. Positive pressure is also applied to an inner surface of the tyre by pressurizing the curing tube.
European patent number 3086934 relates to retreaded tires and methods for manufacturing the same. A tire is retreaded with a pre-cured tread band having a smooth back face and one or more tread grooves with compliant skid base gauge on a front face. The grooves in the pre-cured tread band align with grooves in a tire casing and upon curing conform to the shape of the casing grooves. The tire tread depths are greater than the original tire tread depth of the pre-cured tread band, thereby increasing the wear volume of the tire tread.
Canada patent number 1052063 relates to a vulcanised rubber reclaimed by treating pieces of the rubber to render a surface layer of each piece plastic while the inner core of the piece remains non- plastic. A chemical reagent can be used in the treatment, but it is preferred to render the surface layers of the rubber pieces plastic by a heat treatment which involves direct exposure of the pieces of rubber to either a flame or a heated gas. In a preferred embodiment of the invention vulcanised rubber pieces are dropped under gravity into a flame so that any attached textile residues are burnt away simultaneously with the plasticising of the surface layers of the pieces and the heated pieces then enter a stream of cold air which quenches the heat treatment. Vulcanised rubber articles made from the rubber reclaimed by the method of the invention have improved properties as compared with articles made by the conventional methods of reusing vulcanised rubber.
In order to solve these disadvantages of there is a unique requirement of new and improved design of pre-vulcanised rubber strip for use in the retreading process for motor vehicle tires.
The new and improved design of pre-cure tread are provided with inputs for service on regular roads to exhibit a different type of wear pattern at the end of its service life. The center ribs wear out more than the two shoulder ribs on either side due to inherent tyre design which has Tread Arc Radius. This ingrained tyre design under inflated loaded conditions will induce higher pressure in the center than on shoulders when coming in contact with a flat road surface. This inevitable behavior of retreaded tires is triggered by these inbuilt characteristics in the tyre. This situation is aggravated by the inherent growth of the tyre which in turn increases the tyre diameter in service. This results in the lesser wearing of two shoulder ribs on either side as compared to the center. In other words, when the retreaded tyre completes its full life in the center, as indicated by zero skid depth (photo attached), the shoulders remain less used. As a result of this, more rubber will be left unused on both the shoulder areas at the end of its service life.
This inevitable behavior of tyre on roads is taken to our advantage to balance the input material selection based on raw material cost of the product by having a rubber retread strip with two different compounds. The center crown portion will be having compound with high abrasion resistance and the shoulders will be having a faster abrading compound. The overall material input to the product can be made less expensive without affecting the performance of product.
The information disclosed in this background of disclosure section is only for enhancement of understanding of the general background of the invention and should not be taken as acknowledgement or any form of suggestion that this information forms the prior art already known to person skilled in the art.
OBJECTIVE OF THE INVENTION
One or more problems of the conventional prior art may be overcome by various embodiment of the present invention.
It is the primary object of the present invention to provide an improved design of vulcanised rubber strip for use in retreading process for motor vehicle tires.
The present invention is to provide the retread tires with the improved design vulcanized rubber strips with dual compounds usage which is significantly more efficient in terms of costs, productivity, and performance.
Yet another object of the present invention is to provide a retreaded tyre using dual compounds in the vulcanized rubber strips with the improved design lower rolling resistance which is to reduce the energy loss as tire rolls, decrease the required rolling effort and to improve the vehicle fuel efficiency by suitably designing the rubber compounds.
Yet another object of the present invention is to reduce hysteresis without compromising traction by suitably selecting the rubber compounds thereby giving protection to the used casing and improve its durability.
These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which the preferred embodiment of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
One or more drawbacks of the conventional retreading tyre and the additional advantages provided through the present invention relates to improved design of vulcanized rubber strip for use in retreading process for motor vehicle tires to address the problem of the tyre wear at the end of the retreaded tyre life as mentioned object of the present invention is to provide center crown portion of retread tyre having compound with high abrasion resistance and the shoulder portions of retread tyre having a faster abrading compound.
In an embodiment of the present subject matter relates to an improved design of vulcanized rubber strip for use in retreading process for motor vehicle tires, comprising a vulcanised tread rubber positioned to a tread area of tire casing, wherein the vulcanised tread rubber has a pair of circumferentially continuous annular grooves which divide the vulcanised tread rubber into multiple tread portions comprising a center crown portion and a pair of shoulder portions. The center crown portion has formed with highly abrasion resistant polymers and the pair of shoulder portions has formed with cost effective diluents with carbon blacks (CBs) and mineral fillers having less resistance to abrasive forces.
Accordingly, the design of vulcanised rubber strip using a pre-cure retreading process comprising the steps of: removing damaged or existing tread rubber from a tire casing; preparing a surface of the tire casing; applying a thin layer of uncured gum to the surface of the prepared tire casing; applying new pre-cured tread rubber over the uncured gum, wherein the pre-cured tread rubber is a long, flat strip of the tread rubber into which has been molded or cured of the finished tread i.e. grooves, lugs, tread elements, sipes, and etc.; wrapping circumferentially the tread rubber around the surface of tire casing (10); and trimming and butt-splicing ends of the tread rubber together.
To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF DRAWINGS
Figures 1(a) – (f) illustrate schematic view of different ratios of center crown portion and a pair of shoulder portions of retread tyre rubber, in accordance with an embodiment of the present invention;
Figure 2(a): illustrates transverse sectional view of tyre with low abrasion resistant compound at the shoulder portions before wear, in accordance with an embodiment of the present invention;
Figure 2(b): illustrates transverse sectional view of tyre with low abrasion resistant compound at the shoulder portions after full tread wear, in accordance with an embodiment of the present invention; and
Figure 3: illustrates graphical representation of infrared thermography and the thermal image for improved design of vulcanized rubber, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention as embodied by “an improved design of vulcanized rubber strip for use in retreading process” succinctly fulfils the above-mentioned need(s) in the art. The present invention has objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the spirit or essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
The present invention is thus directed to an improved design of vulcanised rubber strip for use in retreading process for motor vehicle tires. In this improved design has two different compounds which are formed in different portions of the rubber retread strip, wherein the center crown portion of rubber retread strip has formed with highly abrasion resistant polymers and the shoulder portions has formed with cost effective diluents with carbon blacks and mineral fillers having less resistance to abrasive forces. Furthermore, the suitably formulated rubber compounds are provided to impart the lower rolling resistance (RR) and/or lower hysteresis as the case maybe.
Reference may be made to Figures 1(a) – (f) illustrating schematic view of different ratios of center crown portion and a pair of shoulder portions of retread tyre rubber (black shaded portions), in accordance with an embodiment of the present invention. The present subject matter relates to an improved design of vulcanised rubber strip for use in retreading process, comprising of vulcanised tread rubber which has a pair of circumferentially continuous annular grooves (30, 40) divide the vulcanised tread rubber into multiple tread portions comprising a center crown portion (50) and a pair of shoulder portions (60, 70). In accordance with the present invention relates to that the center crown portion (50) and the pair of shoulder portions (60, 70) represent at 20% – 80% of vulcanized tread rubber, especially 55% - 45%.
The different ratios of the center crown portion (50) and the pair of shoulder portions (60, 70), therefore, there are ratios gradually increasing the center crown portion (50) and also decreasing the ratios of the pair of shoulder portions (60, 70). Example: 20 - 80%, 30 – 70%, 40 - 60%, 50 – 50%, 70 - 30% and 80 - 20%, shown in figures 1(a) – (f).
Reference may be made to Figures 2(a) and 2(b) illustrating transverse sectional view of tire with low abrasion resistant compound at the shoulder portions before and after wear, in accordance with an embodiment of the present invention. The present subject matter relates to an improved design of vulcanised rubber strip (100) for use in retreading process, comprising of a vulcanised tread rubber positioned to a tread area (20) of a tire casing (10). The vulcanised tread rubber has a pair of circumferentially continuous annular grooves (30, 40) that divide the vulcanised tread rubber into multiple tread portions comprising a center crown portion (50) and a pair of shoulder portions (60, 70).
Accordingly, the center crown portion (50) of vulcanised tread rubber is made of abrasion resistant polymer material and carbon black (CB) with lower particle size and higher structure, Wherein the pair of shoulder portions (60, 70) of vulcanised tread rubber is made of low abrasion resistant diluent material; carbon black (CB) and mineral fillers having less resistance to abrasive forces. The high levels of abrasion resistant polymer materials consisting of polybutadiene, and the cost effective diluent materials consisting of rubber reclaims, rubber crumbs and carbon blacks (CBs) with suitable particle size and structures.
In accordance with an embodiment of the present subject matter relates to that the design of vulcanised rubber strip using a pre-cure retreading process comprising the steps of: removing damaged or existing tread rubber from a tire casing; preparing a surface of the tire casing; applying a thin layer of uncured gum to the surface of the prepared tire casing; applying new pre-cured tread rubber over the uncured gum, wherein the pre-cured tread rubber is a long, flat strip of the tread rubber into which has been molded or cured of the finished tread i.e. grooves, lugs, tread elements, sipes, and etc.; wrapping circumferentially the tread rubber around the surface of tire casing; and trimming and butt-splicing ends of the tread rubber together.
Accordingly, the retread tires are provided with the improved design of vulcanized rubber strips with dual compounds usage which is significantly more efficient in terms of costs, productivity, and performance. The below table shows the operating ranges and target values for cost effective compound at the shoulder portions:
Example.1 COMPOUND for Crown Portion COMPOUND for Shoulder portions
Range (Mpa) Target (Mpa) Range (Mpa) Target (Mpa)
300% Modulus 8-12 10 6-10 8
Tensile Strength 18-22 20 10-16 13
The below table shows that the retreaded tyre is used by the dual compounds in the vulcanized rubber strips with lower rolling resistance for the new design to reduce the energy loss as tire rolls, decrease the required rolling effort and to improve the vehicle fuel efficiency by suitably designing the rubber compounds.
Example.2 COMPOUND for Crown Portion COMPOUND for Shoulder portions
Range (Mpa) Target (Mpa) Range (Mpa) Target (Mpa)
300% Modulus 10-12 11 10-14 12
Tensile Strength 22-28 25 22-28 25
tand at 600 C 0.08-0.12 0.10 0.06-0.08 0.07
Therefore, with the reduction in tand 600 C will lead to achieve a reduction of 10-18% in coefficient rolling resistance (CRR) for the given retreaded tire.
Further, the below table shows that the present invention is to reduce the hysteresis of the compound by suitably selecting the ingredients, thereby giving the protection of casing, and improving its durability and the stroke retreadtability.

Example.3 COMPOUND for Crown Portion COMPOUND for Shoulder portions
Range
(Mpa) Target (Mpa) Range (Mpa) Target (Mpa)
300% Modulus 8-12 10 10-14 12
Tensile Strength 18-22 20 22-28 25
tand at 600 C 0.16-0.20 0.18 0.06-0.08 0.07
?T (Delta T) 22-28 26 6-8 7
Reference may be made to Figure 3 illustrating graphically the capability of the experimental new design and the low hysteresis compound tested in retreaded tire in the drum test. This is the evident from the infrared thermography graph and the thermal image for improved design of the vulcanized rubber strip. In this graph represents the control and trial values which are measured based on hours.
In accordance with the inevitable behavior of tire on roads is taken to our advantage to the cost effective of the product by having the rubber retread strip with dual compounds or impart the lower rolling resistance (RR) and/or lower hysteresis as the case may be. The center ribs will be having compound with high abrasion resistance and the shoulder ribs will be having a faster abrading compound or lower tand at 60°C or lower hysteresis as the case maybe. The overall cost input to the product can be made less expensive without affecting the other product performance.
It is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. Further, it is to be understood that the present invention is not limited to the methodologies and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described, as these may vary within the specification indicated. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention. One skilled in the art will realise the disclosure may be embodied in other specific forms without departing from the disclosure or essential characteristics thereof.