Patent Application
20110162772
1. Field of the Invention
This invention relates generally to tire repair patches and methods of repairing a damaged tire portion, and more specifically, to tire repair patches and methods of tire repair that facilitate more durable tire repairs.
2. Description of the Related Art
It is commonly known to apply repair patches to a damaged portion of a tire. To facilitate such repairs, it is also customary to prepare the damaged area prior to application of any such patch by substantially removing the damaged portions of any tire reinforcements within the damaged area. Subsequently, the interior surface of a tire surrounding the damaged area, which is associated with an air-impermeable layer called an innerliner, may be cleaned and/or lightly buffed to promote adhesion between the tire and the patch. The patch is then applied to the prepared interior surface of the tire by way of an adhesive.
Current patches provide a substantial amount of rubber material interposed between the tire and the patch reinforcement layer (which contains patch reinforcements, such as cable or cord). The amount of interposed rubber material operates to isolate the patch reinforcements from the tire reinforcements. Patches commonly include polyester or nylon cord reinforcements, which are characterized by having a low tensile modulus, such as 2-4 gigapascals (GPa), and, as such, elongate (i.e., stretch) more at any given tensile force than would be achieved by a higher modulus reinforcement. It is believed the amount of rubber interposed between the tire reinforcements and the patch reinforcements, as well as the use of low tensile modulus reinforcements prevents the patch from achieving improved repair and patch performance. The excess rubber provides an inefficiency with regard to the transfer shear forces between the damaged cords and the isolated patch reinforcements during tire operation. Further, the interposed rubber generally facilitates heat generation during tire operation. Still further, the use of patch reinforcements being characterized by lower tensile moduli may reduce the efficiency in the transferring shear force from the damaged tire cord to the patch reinforcements during tire operation. Accordingly, the following discloses an improved repair patch that at least improves upon the above-stated limitations.
Particular embodiments of the present invention include methods of forming a retreaded tire. Particular embodiments of such methods includes the step of buffing an interior surface of the tire about a perimeter of the damaged tire portion to form a patch receiving surface, the interior surface being buffed to a depth sufficient to place a reinforcement of a tire patch a distance of approximately 3 millimeters or less from a damaged tire reinforcement. Further steps may include covering the damaged portion by applying a pre-assembled patch to the patch receiving surface along the interior surface of the tire, the tire patch sized to cover the damaged portion, such patch including a reinforcement layer interposed between an air-impermeable layer and a tire-contacting surface of the patch, the patch reinforcement being contained within the reinforcement layer and being positioned approximately 3 millimeters or less from the damaged tire reinforcement. Yet another step may include curing the patch to the tire.
Particular embodiments of the present invention include a tire repair patch, the patch including an air-impermeable layer and a reinforcement layer having a plurality of reinforcements, each of the plurality of reinforcements characterized by having a high tensile modulus. The patch may also include a tire-contacting surface, the distance between a majority of the plurality of reinforcements and the contact surface being 3 mm or less.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more detailed descriptions of particular embodiments of the invention, as illustrated in the accompanying drawings wherein like reference numbers represent like parts of the invention.
Particular embodiments of the present invention provide methods and apparatus for repairing a damaged tire section. As further described below, the inventors have discovered that by reducing the distance between reinforcements of a tire repair patch and the damaged reinforcements within a tire, and/or providing patch reinforcements being characterized by having a high tensile modulus, at least an approximately 50% improvement in tire durability has been achieved. This is a significant improvement to the repair tire durability.
Particular embodiments of such methods of repairing a damaged portion of a tire may include the step of preparing the damaged area for repair. Particular embodiments may include the step of forming a recess associated with the damaged tire portion, the opening including a plurality of endings associated with one or more damaged tire reinforcements. In still other embodiments, such methods may include the step of forming an opening associated with the damaged tire portion, the opening including a plurality of endings associated with one or more damaged tire reinforcements. When a tire is damaged, often one or more of the tire reinforcements are also damaged. Prior to repair, the damaged tire portion is prepared for repair. Such preparation may include removing at least a portion of the damage. This includes removing the damaged portion of any damaged tire reinforcement. Accordingly, in particular embodiments, the tire reinforcement is removed until the reinforcement reaches an undamaged portion of the tire. Any other damage may also be removed, which includes other reinforcements and rubber. Ultimately, preparation of the damaged portion may form a recess partially through a thickness of the tire, or an opening through a thickness of the tire. A recess may be formed when it is desirous to only repair a portion of a tire thickness. An opening may be formed when it is desirous to penetrate through the tire to repair the damaged area, such as along the sidewall or shoulder of the tire. Such opening may, in particular embodiments, be formed to expand as it extends toward the exterior of the tire to facilitate better implementation of a filler to the opening subsequent to application of the patch. Damage may occur along the tire sidewalls, or along the tire shoulder, which generally is located between the tire tread and sidewalls. Damage may also occur in the tread area. Because portions of the damaged reinforcements are removed to form the opening, endings of such reinforcements are located about the periphery of the opening.
Particular embodiments of such methods of repair may include, as preparation of the tire for repair, buffing an interior surface of the tire about a perimeter of the damaged tire portion to form a patch receiving surface, the interior surface being buffed to a depth sufficient to place a reinforcement of a tire patch a distance of approximately 3 millimeters or less from a damaged tire reinforcement. It is common to buff the innerliner along an interior surface of a tire, about the periphery of a damaged tire portion. Buffing, which may be achieved by any known tool, manually or automatically, cleans the interior tire surface while also roughing the surface for facilitating proper patch adhesion. The depth of such buff, according to the present invention, however, is more than superficial.
According to particular embodiments, the step of buffing includes buffing the innerliner, as well as other rubber, from the perimeter of the damaged area to form a patch-receiving surface having a depth for positioning the patch reinforcements in close proximity to the tire reinforcements of the damaged tire portion. This increases the efficiency and expediency of shear transfer from the tire reinforcements to the patch reinforcements. In other words, the closer the tire and patch reinforcements are positioned, shearing loads will be transferred quicker to the patch reinforcements, which reduces the shearing deformation between the tire and patch since less deformable rubber exists between the tire and patch reinforcements. Accordingly, the interior perimeter of the damaged area is buffed to a depth that allows the reinforcements of a particular patch to be positioned less than 5 mm from the tire reinforcements associated with the damaged tire portion. In particular embodiments, the buffed depth achieves a distance between tire and patch reinforcements of 3 mm or less. In yet other embodiments, the distance is 2 mm or less. In still other embodiments, the distance is 1 mm or less. It is contemplated that the buffed depth may be substantially zero, that is, the thickness of rubber over the tire reinforcements, which would therefore become at least partially exposed. Further, the buffed profile may gradually extend from the desired depth (closest to the damaged portion) to the unbuffed interior surface of the tire (furthest from the opening). The buffed profile may also be stepped (i.e., non-gradual).
Particular embodiments of such methods includes covering the damaged portion by applying a pre-assembled patch to the patch receiving surface along the interior surface of the tire, the tire patch sized to cover the damaged portion. In particular embodiments, such patch includes a reinforcement layer interposed between an air-impermeable layer and a tire-contacting surface of the patch, the patch reinforcement being contained within the reinforcement layer and being positioned approximately 3 millimeters or less from the damaged tire reinforcement. In particular embodiments, the patch includes an adhesive layer interposed between the tire-contacting surface and the reinforcement layer, the adhesive layer forming a portion of the contacting surface. The adhesive layer may be at least partially uncured for facilitating attachment of the repair patch to the tire. In particular embodiments, the reinforcement and air-impermeable layers are pre-cured. Accordingly, a patch is provided that covers the damaged area of the tire. The patch is sized relative the damaged area such that the patch substantially engages the tire about the perimeter of the damaged area. In the present invention, the patch seals the damaged area to prevent air permeation, but also places patch reinforcements close to the patch tire contact surface for close association with the tire reinforcements upon patch installation. The patch, upon installation, may extend approximately 3 mm or less beyond the interior surface of the tire (i.e., extending within the interior of the tire). In other embodiments, the patch may extend approximately 2 mm or less beyond the interior surface of the tire, and in other embodiments 1 mm or less. In yet other embodiments, the patch is approximately flush with the interior surface of the tire.
In particular embodiments, the patch includes an air-impermeable barrier layer, a reinforcement layer, and an adhesive layer. In such embodiments, the patch thickness is no more than approximately 4-6 mm thick. The barrier layer operates to prevent air permeation from the interior of the tire when pressurized, and may be formed by a butyl rubber, or any other material suitable for such purpose, as known by one of ordinary skill in the art. It is contemplated that the barrier layer may include any desired reinforcement, such as, for example, a nylon, polyester, rayon, or aramid cord, or steel cable. The adhesive layer may comprise any known rubber having adhesive properties in an uncured state, or at least a partially uncured state. In particular embodiments, the adhesive layer is 3 mm or less thick. In other embodiments, the adhesive layer is 1 mm or less thick. In yet other embodiments, the adhesive layer is approximately 0.5 mm or less thick. The adhesive layer, in an embodiment, is attached to the reinforcement layer.
The reinforcement layer generally includes reinforcements for accepting loads from a tire upon which the patch is attached. In particular embodiments, patch reinforcements are characterized by having a high tensile modulus, that is, reinforcements that deform to a lesser degree than other reinforcements when subjected to the same tensile force. A high tensile modulus is quantified as being approximately 8 gigapascals (GPa) or more. In other embodiments, a high tensile modulus reinforcement measures at least approximately 10 GPa. In yet other embodiments, a high tensile modulus reinforcement measures at least approximately 15 GPa, or 20 GPa, or 22 GPa. In particular embodiments, a high tensile modulus reinforcement comprises, for example, aramid or fiberglass cord, or steel cable; however, other reinforcements comprised of other materials, including hybrid materials, may be used.
Aramid cord, in particular embodiments, is characterized as having a tensile modulus of at least approximately 20 GPa, and in other embodiments at least 23 GPa. In still other embodiments, the aramid cord modulus is approximately 20-23 GPa. In a particular embodiment, an approximately 0.7 mm aramid cord reinforcement has a tensile modulus of approximately 22 GPa. Such aramid cord is also characterized as having an ultimate strength, which may typically be around 340 MPa, even though other strengths may be used. A layer containing aramid may include, in particular embodiments, at least an average of approximately 26 aramid cord reinforcements spaced across an inch of such layer (i.e., a minimum of approximately 26 ends per inch), as measured in a direction normal to the lengthwise direction of such reinforcements.
Steel cable, in particular embodiments, is characterized as having a tensile modulus of approximately at least 120 GPa, and in other embodiments at least 180 GPa. In still other embodiments, the steel cable modulus is approximately 120-180 GPa. In a particular embodiment, an approximately 0.7 mm steel cable reinforcement has a tensile modulus of approximately 180 GPa. Such steel cable is also characterized as having an ultimate strength, which may typically be around 380 MPa, even though other strengths may be used. A layer containing steel reinforcements may include, in particular embodiments, at least an average of approximately 8-9 steel cord reinforcements spaced across an inch of such layer (i.e., a minimum of approximately 8-9 ends per inch), as measured in a direction normal to the lengthwise direction of such reinforcements.
By providing a high tensile modulus reinforcement, the patch more expeditiously accepts tensile loads from the tire reinforcements, which is transferred through shear of the rubber between the patch reinforcements and the tire reinforcements. Otherwise, the patch reinforcements may excessively elongate during tire operation, which may facilitate flexing and heat generation. In particular embodiments, the reinforcement is coated with insulation rubber, and in certain embodiments, the insulation rubber provides an exterior coating of approximately 0.3-0.6 mm
It follows, in particular embodiments, that the reinforcement layer can be characterized as a high tensile modulus reinforcement layer. In particular embodiments, the high modulus layer can be characterized as having a minimum effective tensile modulus. A minimum effective tensile modulus of the layer is directly related to the percent amount of reinforcement present within a cross-sectional area of the layer—which is associated with the reinforcement spacing or reinforcement ends per inch within the layer. For example, the arrangement of reinforcements within a reinforcement layer or ply is commonly described as having a particular quantity of ends per inch (that is, an average quantity of reinforcements for each 1 inch width of the layer, as measured in a direction normal to the lengthwise direction of the reinforcements). By knowing the quantity of ends (or reinforcements) per inch, an average reinforcement spacing is also known. Accordingly, the percent amount of reinforcement material present within a cross-section of the layer, as being defined by the reinforcement spacing within the layer, is multiplied by the tensile modulus of such reinforcement material to determine a minimum effective tensile modulus for the layer. Because the reinforcement layer is comprised of both reinforcements and skim or insulation rubber, the layer comprises less than 100% of reinforcement material, and therefore, the effective tensile modulus of the layer is less than the modulus of the reinforcement material.
In one embodiment, the minimum effective tensile modulus can be determined by first determining a cross-sectional area of the reinforcement layer along the particular incremental spacing of reinforcements within the reinforcement layer, which may comprise, for example, the centerline to centerline spacing between adjacent reinforcements. A pre-determined cross-sectional area of the layer may be determined by multiplying the reinforcement height (i.e., thickness or diameter) by the reinforcement spacing within the pre-determined layer cross-sectional area. The percent amount of reinforcement contained within such cross-sectional area is equivalent to the total reinforcement cross-sectional area contained within the pre-determined area, divided by the pre-determined cross-sectional area of the layer. Now, the minimum effective tensile modulus for the reinforcement layer can be obtained by multiplying the percent amount of reinforcement by the tensile modulus of the reinforcement. Accordingly, the resulting effective tensile modulus will be less than that of the reinforcement material, since the tensile modulus of the insulation rubber interposed between the reinforcements is relatively negligible, and therefore, is not accounted for in this calculation.
By way of example, when the reinforcement layer includes 0.7 mm diameter aramid cord reinforcements having a tensile modulus of 20 GPa and being arranged within the layer at 28 ends per inch, the reinforcement spacing equals 1/28 inch or 0.9 mm, while the cross-sectional area of the cord (reinforcement) equals 0.38 mm2 and the total area equals 0.7 mm×0.9 mm, or 0.63 mm2 It follows that the minimum effective tensile modulus for the layer is equivalent to approximately 12 GPa, which is obtained by multiplying the reinforcement tensile modulus of 20 GPa by the percent amount of cross-sectional area of patch reinforcement present within a particular reinforcement spacing (0.38 mm2/0.63 mm2=0.61, or 61%). Accordingly, in particular embodiments, the high modulus reinforcement layer is characterized as having a minimum effective tensile modulus of approximately 5 GPa, and in other embodiments, by a minimum effective tensile modulus of approximately 6 GPa, 10 GPa, or 12 GPa.
In other embodiments, the patch includes a cover layer interposed between the barrier layer and the reinforcement layer. In still other embodiments, one or more gums strips may be positioned about the perimeter of the reinforcement layer to insulate the reinforcement layer from the environment and other portions of the tire. The patch is formed, in particular embodiments, by assembling the various layers of the patch without the adhesive layer, and curing the same. The uncured adhesive layer may then be applied to the patch subsequent the cure, or may be applied during the cure to partially cure the adhesive layer.
Subsequent application of the patch to the tire patch receiving area, particular embodiments of such methods include the step of applying a filler material to the opening along the exterior of the tire, and curing the patch to the tire. Patches are commonly cured to the host tire by various means known within the art, which may include, for example, placing the tire in an autoclave for curing, or locally curing the patch to the tire with a spot curing machine.
The methods described above will now be described and applied below with additional detail, in accordance with the exemplary embodiments shown in
With reference to
With reference to
Along the interior of tire 10, the interior surface 16 is buffed to provide a patch receiving surface 16a about damaged tire portion 12, which may comprise an opening 18 or a recess. This surface may be relatively rough to promote adhesion with patch 10. In the exemplary embodiment shown, the receiving surface 16a includes a gradual or smooth profile, which may be arcuate or linear in shape, extending between unbuffed interior surface 16 and the damages portion 12. In other embodiments, however, the profile of patch-receiving surface 16a may be abrupt, such as by having a stepped or square transition or edge. In the present embodiment, interior tire surface 16 is formed along an air-impermeable layer commonly referred to as an innerliner.
It is also shown that interior surface 16 has been buffed to a particular depth DB to facilitate a close proximity between patch reinforcements 26a and any tire reinforcement 19 associated with damaged portion 12. This is provided to achieve a more durable tire repair. Depth DB facilitates placement of patch reinforcements 26a a distance DR from any underlying tire reinforcements 19, as shown in
With reference to
With reference to
Reinforcement layer 26 generally comprises patch reinforcements 26a coated with rubber insulation 26b. In particular embodiments, patch reinforcements 26a are characterized by having a high tensile modulus, that is, reinforcements that deform to less than other (lower tensile modulus) reinforcements when subjected to the same tensile force. A high tensile modulus may be quantified as being approximately 8 gigapascals (GPa) or more. In other embodiments, a high tensile modulus measures approximately 10 GPa or more. In yet other embodiments, a high tensile modulus measures approximately 15 GPa or more. In still other embodiments, a high tensile modulus measures approximately 20 GPa, or 22 GPa, or more.
In particular embodiments, high tensile modulus reinforcements comprise aramid or fiberglass cord, or steel cable. Particular embodiments of aramid and steel reinforcements are described above. High tensile modulus reinforcements 26a used in reinforcement layer 26 may, however, be formed of any other materials having a high tensile modulus. Further, reinforcement layer 26 may include hybrid reinforcements formed of both high tensile modulus reinforcements or filaments and other non-high modulus reinforcements or filaments. For example, a high modulus reinforcement may include aramid (a high tensile modulus material) and nylon (a lower modulus material) reinforcements or filaments. In such example, a 0.7 mm aramid-nylon reinforcement 26a has a tensile modulus of at least approximately 8-10 GPa. Other non-high tensile modulus materials include polyester. In still other embodiments, reinforcement layer 26 may be formed of both high and lower tensile modulus reinforcements. By providing high tensile modulus reinforcements, the patch more expeditiously accepts loads from the tire reinforcements by reducing deflections (i.e., the elasticity) between the tire and patch.
Reinforcements 26a of reinforcement layer 26 are generally distributed within the layer 26 as desired. Such distribution is commonly expressed or quantified as providing a quantity of endings (i.e., reinforcements) per inch, which means that for each inch of layer 26, measured in a direction normal to the lengthwise direction of reinforcements 26a, there are, on average, a specified number of reinforcements 26a. As stated above, reinforcement layer 26 is formed of high tensile modulus reinforcements, such as aramid or steel. In particular embodiments, reinforcement layer 26 is formed of aramid reinforcements 26a arranged to provide at least 20 ends per inch (i.e., the distribution of aramid reinforcements 26a within layer 26 provide 20 or more reinforcements per inch). In other embodiments, the aramid reinforcement layer 26 includes 26 or more ends per inch. In yet other embodiments, aramid reinforcement layer 26 includes 26-30 ends per inch.
In particular embodiments, reinforcement layer 26 may be described as being a high tensile modulus reinforcement layer. As described above, a high tensile modulus reinforcement layer 26 may be characterized as having a minimum effective tensile modulus. In particular embodiments, reinforcement layer 26 may be characterized as having a minimum effective tensile modulus of at least approximately 5 GPa. In other embodiments, the minimum effective tensile modulus of reinforcement layer 26 is at least approximately 6 GPa, 10 GPa, or 12 GPa.
In particular embodiments, a second reinforcement layer 27 may be placed along the interior side of the high-modulus reinforcement layer, as exemplarily shown in
When applying the patch 20 to a tire 10, in a particular embodiment, the patch reinforcements 26a are substantially parallel to the lengthwise orientation of the tire reinforcements 19. Further, in particular embodiments, patch 20 applied to the tire 10 such that lengthwise direction of patch reinforcements 26a extends in substantially the same direction as the lengthwise direction of tire reinforcements 19, which, in particular embodiments, which may extend in a substantially radial direction of tire 10 as exemplarily shown in
In particular embodiments, patch 10 is applied to the damaged portion 12 so to cover and also overlap the perimeter of the damaged portion, such as is shown in an exemplary embodiment in
Additional material, such as gum strip 28, may be placed about the sides of reinforcement layer 26 to insulate layer 26 and/or to provide a more uniform patch thickness beyond the reinforcement layer 26. With reference to the embodiments shown in
To facilitate a close relationship between patch reinforcements 26a and tire reinforcements 19, the thicknesses of patch reinforcement insulation 26b and adhesion layer 30 are controlled. Patch reinforcement thickness is referred to a TI, while adhesion layer thickness is referred to as TA. As stated previously, the tire interior surface 16 is also buffed to a depth of DB adjacent the perimeter of damaged portion 12, for the purpose of facilitating a close association between patch and tire reinforcements. Accordingly, in buffing to a depth of DB, a thickness of material may remain between tire reinforcements 19 and the buffed interior surface 16a, which is referred to as TO. Because it is desirous for patch reinforcements 26a to be positioned a distance DR from tire reinforcements 19 that is 3 mm or less, it follows that DR=TI+TA+TO≦3 mm In facilitating achievement of a 3 mm or less spacing, it is contemplated that in various embodiments the thickness of insulation TI is between 0.3-0.6 mm, and the thickness of adhesive layer TA is approximately 0.5 mm Still, thicknesses TI, TA, and TO may comprise any thickness so long as the sum of all is 3 mm or less. It follows that TO may be approximately zero, which assumes that the interior tire surface 16 has been buffed to expose tire reinforcements 19, or any other dimension less than 3 mm.
Upon installation, in particular embodiments, patch 20 may remain approximately flush with interior tire surface 16, or may extend inwardly into the tire beyond the interior tire surface 16. Accordingly, in particular embodiments, patch 20 (or interior tire patch surface 32) extends approximately 3 mm or less beyond the interior surface 16 of the tire. In other embodiments, patch 20 extends approximately 2 mm or less beyond the interior surface 16 of the tire, and in other embodiments 1 mm or less.
To determine the improvements of the present invention, several tests were run. Specifically, tire durability tests were run, during which tires having been repaired with particular patch configurations were run at a constant speed of 100 kilometers per hour (Kph) while pressurized at 100 psi. Loads were also increase in 5% increments beginning at 85% of the maximum rate load of 2800 Kg. The tires used were 275/80R22.5 sized truck tires having a load range G. The damaged portion for each tire was located along the upper sidewall and was defined by a 25 mm wide by 70 mm high area. Four patch configurations were tested to determine the distance each repaired tire could travel prior to failure under the test conditions. The results were normalized against the results obtained for a conventional patch, the conventional patch having four polyester plies (layers) of reinforcements. All patches tested were aligned relative to the tire carcass reinforcements such that the patch reinforcements extended in substantially the same lengthwise direction as the tire carcass reinforcements, which extended in a radial direction of the tire (such as shown in
While this invention has been described with reference to particular embodiments thereof, it shall be understood that such description is by way of illustration and not by way of limitation. Accordingly, the scope and content of the invention are to be defined only by the terms of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US08/75860 | 9/10/2008 | WO | 00 | 3/8/2011 |
