Method of retreading a tire casing using an innerliner compound or a sealant material

Abstract

A method of retreading a tire casing that includes the steps of inspecting the casing for injuries, buffing the casing to remove a tread, and applying an innerliner compound made up of a curable material or a sealant material made up of material that is configured to remain at least partially uncured. The innerliner compound or sealant material has at least one of surface tension properties, adhesion properties, or viscosity properties such that the innerliner compound or sealant material does not move from an application location under the force of gravity. The method further includes the steps of applying a new tread to the casing, and curing the casing and the new tread to bond the new tread to the casing.

Description

METHOD OF RETREADING A TIRE CASING USINGAN INNERLINER COMPOUND OR A SEALANT MATERIALFIELD OF INVENTION

[0001] The present disclosure relates generally to the field of retreading tires, and more specifically to a method of retreading a tire casing using an innerliner compound or a sealant material.BACKGROUND

[0002] Retreaded tires have been available for many years and provide an economical way to gain additional use out of a tire after the original tread has become worn. The life of a tire may be extended by applying a new tread to a used tire casing. Retreaded tires offer an economical and environmentally friendly alternative to new tires. In particular, compared to a completely new tire, retreaded tires require less energy and materials to manufacture and reduce landfill waste.

[0003] As is known in the art, the retreading process can include an inspection step where the used tire, otherwise known as a casing, is examined for injuries such as punctures or other damage. The retreading process also includes a buffing step, which is the removal of the remaining tread from the casing. Removing the tread can be accomplished by a buffing machine that grinds away the old tread and leaves a buffed surface that is generally uniform about the circumference of the casing. After the casing is buffed, any injuries are repaired and a new' tread may then be applied to the buffed surface.

[0004] The process of inspecting and repairing the casing is critical, as the failure to repair injuries before the new tread is applied may result in a tire that does not hold air, rendering it unusable. This wastes considerable resources. While methods have been developed to detect tire injuries, it has been found that such methods are not faultless.SUMMARY OF THE INVENTION

[0005] In one embodiment, a method of retreading a tire casing includes the steps of inspecting the casing for injuries, buffing the casing to remove a tread, and applying an innerliner compound. The innerliner compound is made up of a curable material and has at least one of surface tension properties, adhesion properties, or viscosity properties such that the innerliner compound does not move from an application location under the force of gravity. The method further includes the steps of applying a new tread to the casing, and curing the casing and the new tread to bond the new tread to the casing.

[0006] In another embodiment, a method of retreading a tire casing includes the steps of inspecting the casing for injuries, buffing the casing to remove a tread, and applying a sealant material. The sealant material is made up of material that is configured to remain at least partially uncured and has at least one of having at least one of surface tension properties, adhesion properties, or viscosity properties such that the sealant material does not move from an application location under the force of gravity. The method further includes the steps of applying a new tread to the casing, and curing the casing and the new tread to bond the new tread to the casing.BRIEF DESCRIPTION OF DRAWINGS

[0007] In the accompanying drawings, structures are illustrated that, together with the detailed description provided below, describe exemplary embodiments of the claimed invention. Like elements are identified with the same reference numerals. It should be understood that elements shown as a single component may be replaced with multiple components, and elements shown as multiple componentsmay be replaced with a single component. The drawings are not to scale and the proportion of certain elements may be exaggerated for the purpose of illustration.

[0008] Figure 1 is a cross-section view of an exemplary7pneumatic tire,

[0009] Figure 2 is a flow chart showing the steps of an exemplary method of retreading the tire of Figure 1, and

[0010] Figure 3 is a flow chart showing the steps of another exemplary7method of retreading the tire of Figure 1.DETAILED DESCRIPTION OF THE INVENTION

[0011] The following includes definitions of selected terms employed herein. The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be w ithin the definitions.

[0012] “Axial” and “axially” refer to a direction that is parallel to the axis of rotation of a tire.

[0013] ‘Circumferential” and “circumferentially” refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

[0014] “Radial” and “radially” refer to a direction perpendicular to the axis of rotation of a tire.

[0015] “Tread” as used herein, refers to that portion of the tire that comes into contact with the road or ground under normal load.

[0016] While similar terms used in the follow ing descriptions describe common tire components, it should be understood that because the terms carry slightly different connotations, one of ordinary skill in the art would not consider any one of the following terms to be purely interchangeable with another term used to describe a common tire component.

[0017] Directions are stated herein with reference to the axis of rotation of the tire. The terms “upward” and “up ardly” refer to a general direction towards the tread of the tire, whereas “downward” and “downwardly” refer to the general direction towards the axis of rotation of the tire. Thus, when relative directionalterms such as '‘upper’’ and "lower” or "top” and “bottom” are used in connection with an element, the “upper” or “top” element is spaced closer to the tread than the “lower” or “bottom” element. Additionally, when relative directional terms such as “above” or “below” are used in connection with an element, an element that is “above” another element is closer to the tread than the other element.

[0018] The terms '‘inward” and “inwardly” refer to a general direction towards the equatorial plane of the tire, whereas “outward” and “outwardly” refer to a general direction away from the equatorial plane of the tire and towards the side of the tire. Thus, when relative directional terms such as “inner” and “outer” are used in connection with an element, the “inner” element is spaced closer to the equatorial plane of the tire than the “outer” element.

[0019] A cross section of an exemplar}' tire 11 is show n in Figure 1. The tire includes a carcass 101 extending between a pair of axially-spaced beads 102, 102'.The carcass may include one or more body plies (not shown). Abrasion strips 103, 103' partially encase the carcass 101 at or near the beads 102, 102'. The tire 11 further includes opposing sidewalls 104, 104' and a tread 105. The tread 105 forms the top surface of the tire 100. A subtread 106 is disposed below- the tread 105, an undertread 107 is disposed below the subtread 106, and a belt package 108 is disposed below the undertread 107. The belt package 108 may include a plurality of belts (not shown) and is positioned above the carcass 101. An innerliner 109 is disposed on an interior of the carcass 101 relative to the tread 105. As appreciated by those of ordinary skill in the art, the tire 11 may also include various other components, such as, but not necessarily limited to, tread shoulders, cap plies, belt wedges, or belt shoulders (not shown).

[0020] The tread 105 may include tread features such as, but not necessarily limited to, blocks, ribs, sipes, or grooves that provide desired performance characteristics. After the tire 11 is put into service, the tread 105 begins to wear due to contact with an underlying surface such as an asphalt or concrete road. After the tread 105 experiences a certain amount of wear, the tread features may no longer provide the desired performance characteristics. A used tire with worn tread may also be referred to as a “casing.” The tread 105 of the casing may be replaced whileretaining the remainder of the tire 11 structure using a process known as ‘'retreading.”

[0021] An exemplary7retreading method is described below with reference to Figure 2. The method begins with an initial inspection step 1010. During the initial inspection step 1010. a worker visually inspects the casing. The casing may be placed in equipment that is configured to facilitate visual inspection of the interior of the casing, such as a mechanical spreader. The worker visually inspects various parts of the casing including, but not necessarily limited to, the sidewalls, the innerliner. the beads, and the tread. In addition to performing a visual inspection, the worker may use his or her hands to feel for foreign objects or injuries to the casing. Any injuries are marked for repair later in the retreading method.

[0022] Next, the retreading method moves to an electrical inspection step 1020.The electrical inspection step 1020 utilizes a machine that produces an electric impulse to identify injuries that may have been missed during the initial inspection. The electrical impulse causes injured areas of the casing to produce a spark that is visible to the worker, thereby facilitating identification of casing injuries.

[0023] One goal of the initial inspection step 1010 and the electrical inspection step 1020 is to identify casings with any injuries that are too severe to repair. Such casings will be rejected for retreading and will not proceed further in the retreading method.

[0024] Casings that pass the initial inspection step 1010 and the electrical inspection step 1020 proceed to a shearography step 1030. The shearography step 1030 is a form of non-destructive testing that uses a machine with laser technology that optically inspects parts of the casing, such as the belt package or body plies, to identify any separation issues between the layers of material that make up these parts of the casing. The machine may also identify7other injuries that may have been missed during the previous inspection steps. The machine may subject the casing to a vacuum in order to stress the casing to spotlight separation issues. Any separation issues or other injuries that are too severe will result in the casing being rejected from the retreading method and will not proceed further.

[0025] If the casing passes the shearography step 1030, it is then subjected to the buffing step 1040. The buffing step 1040 utilizes a machine that removes the tread 105 in order to provide a uniform surface. The buffing step 1040 may also, but not necessarily, remove or at least partially remove the subtread 106 or undertread 107. The machine may be configured to buff the casing until the casing has a predetermined width and radius. The buffing step 1040 may also impart the casing with a desired texture that facilitates adhesion of the new tread.

[0026] Once the casing is buffed, it then moves to a repair process step 1050.During the repair process step 1050, a worker repairs the injuries identified during the initial inspection step 1010, the electrical inspection step 1020, and the shearography step 1030. The repair process step 1050 may utilize procedures including, but not necessarily limited to, drilling, cleaning, grinding, trimming, applying rubber cement, extruding rubber material, and adhering patch material.

[0027] Next , an innerliner compound is applied to the casing at 1055. The innerliner compound fills and repairs any holes or injuries in the casing and may be applied using various techniques including, but not necessarily limited to, pumping, spraying, hand application, or extrusion. The innerliner compound is configured to have sufficient surface tension properties, adhesion properties, or viscosity¬ properties to remain in place after application. In other words, once the innerliner compound is applied, it generally will not sag, run, or otherwise move from its application location under the force of gravity. The innerliner compound is made up of a curable material, such as butyl rubber with carbon black filler and curatives. As will be appreciated by those of ordinary skill in the art, the innerliner compound may be applied to the casing even in instances where the casing has no injuries to repair.

[0028] In alterative embodiments, the innerliner compound may be made up of any appropriate material including, but not limited to, synthetic polymers such as, but not limited to, synthetic polyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene, poly(ethylene-co- propylene), poly(styrene-co-butadiene), poly(styrene-co-isoprene), and poly(styrene-co-isoprene-co-butadiene), poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene), poly sulfiderubber, acrylic rubber, urethane rubber, silicone rubber, and epichlorohydrin rubber. The innerliner compound may also include other various ingredients such as, for example, accelerators, oils, waxes, scorch inhibiting agents, processing aids, zinc oxide, tackifying resins, reinforcing resins, fatty acids such as stearic acid, peptizers, antiozonants, and one or more additional rubbers. The innerliner compound may also include inorganic fillers (e.g., silica, aluminum hydroxide, magnesium hydroxide, clays (hydrated aluminum silicates), chemically functionalized clays, and mixtures thereof) or organic fillers (e.g., carbon black or starch).

[0029] After the innerliner compound is applied, a cushion step is performed at 1060. During the cushion step 1060, a thin layer of uncured rubber (otherwise known as “cushion gum”) is applied to the buffed surface of the casing. The cushion gum may fill voids in the casing that are left from the repair process step 1050 and prepares the casing for application of the new tread.

[0030] Next, the retreading method proceeds to a building step 1070, w here the new7tread is first introduced to the casing. In particular, a machine applies a precured tread with desired tread features (e.g., blocks, ribs, sipes, grooves, etc.) to the cushion gum that was applied during the cushion step 1060. The building step 1070 may also include a process known as “stitching,” where a machine applies pressure to the new7tread and casing to remove trapped air and improve adhesion between the new7tread, the cushion gum, and the casing.

[0031] After the building step 1070 is complete, the casing then goes to an enveloping step 1080. At the enveloping step 1080, the casing and new7tread assembly is placed in a flexible rubber envelope. Rings are then used to seal the envelope, thereby creating an airtight chamber. Then, air is evacuated from the chamber, which creates a vacuum that causes the envelope to apply uniform pressure to the casing and new tread assembly. The vacuum created during the enveloping step 1080 may cause the innerliner compound that was applied during the repair process step 1050 to be pulled into any holes or injuries, thereby providing a more robust repair. In alternative embodiments, a separate vacuuming step may be employed to pull the innerliner compound into any holes or injuries.

[0032] The enveloped casing is then cured at 1090. The curing step 1090 involves placing the sealed envelope, with the casing and new tread assembly contained therein, in a curing chamber. The chamber is sealed and brought to a specific temperature and pressure for a specified time period, which causes the previously uncured cushion gum to cure, thereby permanently bonding the new tread to the casing. The chamber may be brough to a temperature in the range of 210-260 °F, a pressure in the range of 65-105 psi, and remain at this temperature and pressure for a time period in the range of 120-210 minutes. These values are merely exemplary and, as understood by those of ordinary skill in the art, other values may be used depending on the composition or construction of the casing. This process also cures the innerliner compound, thereby further enhancing the durability of the innerliner compound repairs. The curing step 1090 concludes by removing the retreaded tire from the envelope.

[0033] The retreading process concludes with a final inspection step 1100. The final inspection step 1100 may utilize procedures including, but not necessarily limited to, visual inspection, measurement of retreaded tire dimensions, and painting the retreaded tire with weather resistant paint.

[0034] The innerliner compound applied during the repair process step 1050 advantageously ensures that any holes or other injuries that may have been missed during the retreading process are filled, thereby ensuring that the retreaded tire is airtight and improving scrap rate. Moreover, because the innerliner compound is configured to cure, it does not pose any potential issues to future retreading, as may be the case with known sealant compounds.

[0035] Another exemplary retreading method is described below with reference to Figure 3. The retreading method of Figure 3 is substantially the same as the retreading method of Figure 2. Like steps will be identified with like numerals increased by a factor of “1000.

[0036] The method begins with an initial inspection step 2010. During the initial inspection step 2010, a worker visually inspects the casing. The casing may be placed in equipment that is configured to facilitate visual inspection of the interior of the casing, such as a mechanical spreader. The worker visually inspectsvarious parts of the casing including, but not necessarily limited to, the sidewalls, the innerliner, the beads, and the tread. In addition to performing a visual inspection, the worker may use his or her hands to feel for foreign objects or injuries to the casing. Any injuries are marked for repair later in the retreading method.

[0037] Next, the retreading method moves to an electrical inspection step 2020.The electrical inspection step 2020 utilizes a machine that produces an electric impulse to identify injuries that may have been missed during the initial inspection. The electrical impulse causes injured areas of the casing to produce a spark that is visible to the worker, thereby facilitating identification of casing injuries.

[0038] One goal of the initial inspection step 2010 and the electrical inspection step 2020 is to identify casings with any injuries that are too severe to repair. Such casings will be rejected for retreading and will not proceed further in the retreading method.

[0039] Casings that pass the initial inspection step 2010 and the electrical inspection step 2020 proceed to a shearography step 2030. The shearography step 2030 is a form of non-destructive testing that uses a machine with laser technology that optically inspects parts of the casing, such as the belt package or body plies, to identify any separation issues between the layers of material that make up these parts of the casing. The machine may also identify other injuries that may have been missed during the previous inspection steps. The machine may subject the casing to a vacuum in order to stress the casing to spotlight separation issues. Any separation issues or other injuries that are too severe will result in the casing being rejected from the retreading method and will not proceed further.

[0040] If the casing passes the shearography step 2030, it is then subjected to a buffing step 2040. The buffing step 2040 utilizes a machine that removes the tread 105 in order to provide a uniform surface. The buffing step 2040 may also, but not necessarily, remove or at least partially remove the subtread 106 or undertread 107.The machine may be configured to buff the casing until the casing has a uniform, predetermined width and radius. The buffing step 2040 may also impart the casing with a desired texture that facilitates adhesion of the new tread.

[0041] Once the casing is buffed, it then moves to a repair process step 2050.During the repair process step 2050, a worker repairs the injuries identified during the initial inspection step 2010, the electrical inspection step 2020, and the shearography step 2030. The repair process step 2050 may utilize procedures including, but not necessarily limited to, drilling, cleaning, grinding, trimming, applying rubber cement, extruding rubber material, and adhering patch material.

[0042] Next, a sealant material is applied to the casing at 2055. The sealant material fills and repairs any holes or injuries in the casing and may be applied using various techniques including, but not necessarily limited to, pumping, spraying, hand application, or extrusion. The sealant material is configured to have sufficient surface tension properties, adhesion properties, or viscosity properties to remain in place after application. In other words, once the sealant material is applied, it generally will not sag, run, or otherwise move from its application location under the force of gravity. The sealant material is further configured to remain at least partially uncured, and may be made up of butyl rubber, plasticizer, carbon black filler. As will be appreciated by those of ordinary skill in the art, the sealant material may be applied to the casing even in instances where the casing has no injuries to repair.

[0043] In alternative embodiments, the sealant material may be made up of any appropriate material including, but not limited to, a composition deriving from a butyl rubber emulsion that includes at least one additional rubber component selected from the group consisting of diene type unsaturated hydrocarbon polymer emulsions and a natural rubber latex, at least one saturated hydrocarbon polymer emulsion, a crosslinking agent for the rubbers and a crosslinking activator. As another example, the sealant material may include a uniform dispersion of small quinoid particles without the use of polar, organic solvents to solubilize the curing agent. As yet another example, the sealant material may include an at least partially- decomposed polyisobutylene. According to another example, the sealant material includes a polyurethane composition including those that may be formed from a cast or a millable polyurethane or a sulfur-curable diene-containing polyurethane precursor.

[0044] After the sealant material is applied, a cushion step is performed at 2060.During the cushion step 2060, a thin layer of uncured rubber (otherwise known as “cushion gum'’) is applied to the buffed surface of the casing. The cushion gum may fill voids in the casing that are left from the repair process step 2050 and prepares the casing for application of the new tread.

[0045] Next, the retreading method proceeds to a building step 2070, where the new tread is first introduced to the casing. In particular, a machine applies a precured tread with desired tread features (e.g., blocks, ribs, sipes, grooves, etc.) to the cushion gum that was applied during the cushion step 2060. The building step 2070 may also include a process known as “stitching,” where a machine applies pressure to the new tread and casing to remove trapped air and improve adhesion between the new tread, the cushion gum, and the casing.

[0046] After the building step 2070 is complete, the casing then goes to an enveloping step 2080. At the enveloping step 1080, the casing and new tread assembly is placed in a flexible rubber envelope. Rings are then used to seal the envelope, thereby creating an airtight chamber. Then, air is evacuated from the chamber, which creates a vacuum that causes the envelope to apply uniform pressure to the casing and new tread assembly. The vacuum created during the enveloping step 2080 may cause the sealant material that was applied during the repair process step 2050 to be pulled into any holes or injuries, thereby providing a more robust repair. In alternative embodiments, a separate vacuuming step may be employed to pull the sealant material into any holes or injuries.

[0047] The enveloped casing is then cured at 2090. The curing step 2090 involves placing the sealed envelope, with the casing and new tread assembly contained therein, in a curing chamber. The chamber is sealed and brought to a specific temperature and pressure for a specified time period, which causes the previously uncured cushion gum to cure, thereby permanently bonding the new tread to the casing. The chamber may be brough to a temperature in the range of 210-260 °F, a pressure in the range of 65-95 psi, and remain at this temperature and pressure for a time period in the range of 125-210 minutes. These values are merely exemplary and, as understood by those of ordinary skill in the art, othervalues may be used depending on the composition or construction of the casing. Because the sealant material is configured to remain at least partially uncured, it remains at least partially flowable after the curing step 2090, which may provide advantages once the retreaded tire is put into use. The curing step 2090 concludes by removing the retreaded tire from the envelope.

[0048] The retreading process concludes with a final inspection step 2100. The final inspection step 2100 may utilize procedures including, but not necessarily limited to, visual inspection, measurement of retreaded tire dimensions, and painting the retreaded tire with weather resistant paint.

[0049] The sealant material applied during the repair process 2200 advantageously ensures that any holes or other injuries that may have been missed during the retreading method are repaired, thereby ensuring that the retreaded tire is airtight and improving scrap rate. Moreover, because the innerliner compound is configured to remain at least partially uncured, it may allow for extended mobility during the life of the retreaded tire by flow ing into and sealing any holes or other injuries that may occur during use.

[0050] As one of ordinary' skill in the art will appreciate, certain steps of the method described above with reference to Figure 2 or the method described above with reference to Figure 3 may be performed in a different order than what has been expressly described without departing from the spirit and scope of the invention. As one of ordinary' skill in the art will also appreciate, certain steps of the method described above with reference to Figure 2 or the method described above with reference to Figure 3 may be omitted without departing from the spirit and scope of the invention. Additionally, as will be appreciated by' one of ordinary' skill in the art, the method described above w ith reference to Figure 2 or the method described above with reference to Figure 3 may be used on any tire and are not limited for use with a tire having the structure depicted in Figure 1.

[0051] To the extent that the term ‘’includes’’ or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g.. A or B)it is intended to mean “A or B or both.’’ When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Gamer, A Dictionary of Modem Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” Furthermore, to the extent the term “connect” is used in the specification or claims, it is intended to mean not only “directly connected to,” but also “indirectly connected to” such as connected through another component or components.

[0052] While the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the application, in its broader aspects, is not limited to the specific details, the representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant’s general inventive concept.

Claims

CLAIMSWhat is claimed is:

1. A method of retreading a tire casing comprising the steps of:inspecting the casing for injuries;buffing the casing to remove a tread;applying an innerliner compound, the innerliner compound being made up of a curable material and having at least one of surface tension properties, adhesion properties, or viscosity properties such that the innerliner compound does not move from an application location under the force of gravity;applying a new tread to the casing; andcuring the casing and the new tread to bond the new tread to the casing.

2. The method of claim 1, wherein the innerliner compound cures during the step of curing the casing and the new tread.

3. The method of claim 1, wherein the step of applying the inner liner compound includes at least one of pumping, spraying, hand applying, or extruding the innerliner compound.

4. The method of claim 1, wherein the step of inspecting the casing for injuries includes using a machine that produces electric impulse that causes injuries to produce a visible spark.

5. The method of claim 1 further comprising the step of performing shearography on the casing.

6. The method of claim 1 further comprising the step of applying cushion gum to the casing before the step of applying a new tread to the casing.

7. The method of claim 6, wherein the cushion gum is configured to cure during the step of curing the casing and the new tread, the cushion gum permanently bonding the new tread to the casing.

8. The method of claim 1 further comprising the step of placing the casing and the new tread in an envelope before the step of curing the casing and the new tread, the envelope forming an airtight chamber.

9. The method of claim 8 further comprising the step of evacuating air from the airtight chamber to cause the envelope to apply uniform pressure to the casing and the new7tread.

10. The method of claim 9, wherein the step of curing the casing and the new tread includes subjecting the envelope with the casing and the new tread contained therein to a predetermined temperature and pressure for a predetermined time after the step of evacuating air from the airtight chamber.

11. A method of retreading a tire casing comprising the steps of:inspecting the casing for injuries;buffing the casing to remove a tread;applying a sealant material, the sealant material being made up of material that is configured to remain at least partially uncured and having at least one of having at least one of surface tension properties, adhesion properties, or viscosity7properties such that the sealant material does not move from an application location under the force of gravity;applying a new tread to the casing; andcuring the casing and the new tread to bond the new tread to the casing.

12. The method of claim 11, wherein the sealant material remains at least partially uncured during the step of curing the casing and the new tread.

13. The method of claim 11, wherein the step of applying the sealant material includes at least one of pumping, spraying, hand applying, or extruding the sealant material.

14. The method of claim 11, wherein the step of inspecting the casing for injuries includes using a machine that produces electric impulse that causes injuries to produce a visible spark.

15. The method of claim 11 further comprising the step of performing shearography on the casing.

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