This invention relates to a method and apparatus for making and applying a puncture sealant to tire components mounted upon a tire building drum.
It is known in the prior art to apply puncture sealants made of puncture sealing rubber or plastic material on the crown portion of the tire so that when a sharp object such as a nail pierces the tire, the tire sealant forms a seal around the puncture. Tire sealants of this nature tend to flow or be soft resulting in a tendency to migrate towards the center portion of the tire due to centrifugal force as the tire is rotated at high speeds. Thus the outer portions of the crown have reduced sealant volume due to migration of the sealant towards the center. It is known in the prior art to compartmentalize a sealant into multiple cells such as shown in U.S. Pat. No. 2,877,819 or U.S. Pat. No. 4,388,261. One disadvantage to compartmentalizing the sealant into multiple cells is that the manufacturing process is costly. Further, having too many compartments may impede the effective flow of the sealant needed to seal a puncture. Further, using an extruder to manufacture the sealant into compartments is costly and requires additional manufacturing steps. Thus it is desired to provide a tire and a low cost manufacturing method for providing puncture sealant in a tire which does not migrate during use.
“Aspect Ratio” means the ratio of a tire's section height to its section width.
“Axial” and “axially” mean the lines or directions that are parallel to the axis of rotation of the tire.
“Carcass” means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction; it can also refer to the direction of the sets of adjacent circular curves whose radii define the axial curvature of the tread as viewed in cross section.
“Cord” means one of the reinforcement strands, including fibers, which are used to reinforce the plies.
“Inner Liner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
“Ply” means a cord-reinforced layer of elastomer-coated, radially deployed or otherwise parallel cords.
“Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.
“Radial Ply Structure” means the one or more carcass plies or which at least one ply has reinforcing cords oriented at an angle of between 65° and 90° with respect to the equatorial plane of the tire.
“Radial Ply Tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire.
“Sidewall” means a portion of a tire between the tread and the bead.
“Skive” or “skive angle” refers to the cutting angle of a knife with respect to the material being cut; the skive angle is measured with respect to the plane of the flat material being cut.
“Laminate structure” means an unvulcanized structure made of one or more layers of tire or elastomer components such as the innerliner, sidewalls, and optional ply layer.
The structure, operation, and advantage of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings wherein:
Referring now to
The sealant 7 may comprise any suitable sealant composition known to those skilled in the art, such as rubber or elastomer compositions and plastic compositions. One suitable polymer composition suitable for use is described in U.S. Pat. No. 4,895,610, the entirety of which is incorporated by reference. The polymer compositions described therein include the following composition by weight: 100 parts of a butyl rubber copolymer, about 10 to about 40 parts of carbon black, about 5 to about 35 parts of an oil extender, and from about 1 to 8 parts of a peroxide vulcanizing agent. A second polymer composition includes the following composition by weight: 100 parts of a butyl rubber copolymer, about 20 to about 30 parts of carbon black, about 8 to about 12 parts of an oil extender, and from about 2 to 4 parts of a peroxide vulcanizing agent.
The sealant 7 may also comprise a colored polymer composition as described in U.S. Pat. No. 7,073,550, the entirety of which is incorporated herein by reference. The colored polymer composition is comprised of, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber exclusive of carbon black:
Another sealant polymer composition which may be utilized by the invention is described in U.S. Pat. No. 6,837,287, the entirety of which is hereby incorporated by reference.
Further, any sealant polymer composition may also be used with the invention that has a polymer composition of butyl rubber and an organoperoxide vulcanizing agent which becomes activated at high temperatures above 100 deg C.
The sealant 7 may be applied directly to a tire component mounted on the tire building drum using a gear pump extruder. The gear pump extruder may have a shaping die to extrude the sealant in a continuous strip onto the rotating tire drum. The strip is spirally wound onto the tire building drum wherein the edge of each strip abuts with an adjacent strip. The sealant may also be extruded to a desired shape and then applied to the tire building drum using a machine applier or by hand.
Next, a strip of elastomer, gum strip of rubber, fabric, dipped fabric, or any other suitable material known to those skilled in the art (hereinafter, “divider strip”) is applied over the axially inner end 24. The divider strip 26 has a sufficient width to extend from the top surface 25 of the sealant outer zone 10, along the entire angled end 24 and then directly onto a portion of the tire liner 27. The width of the divider strip may range from about 0.5 to about 3 inches, depending upon the thickness of the sealant. The thickness of the strip may be, for example, about 0.05 to 0.1 inches. The divider strip is applied circumferentially around the entire axially inner end 24 and then spliced together, in order to form a barrier between the axially outer zones and the axially inner zone(s). The divider strip may be applied manually or by machine, such as by a gear pump extruder.
Next one or more axially inner zones 15 of the sealant are applied to the tire building drum. The axially inner zone(s) 15 has a first and second surface 30 for mating with the respective divider strip 26. The first and second surfaces 30 are preferably shaped at the same angular inclination as the abutting surfaces 24. The axially outer zones 10, 20 and the one or more inner zones 15 and the two or more divider strips 26 are closely spaced in an abutting relationship.
A cover layer 9 is applied directly over the liner, the sealant axially outer angled end 22 and the upper surface 25 of the axially outer zones 10, 20 and over the upper surface 16 of the sealant in the one or more axially inner zones 15. In particular, the liner, divider strip 26 and the barrier layer 9 upon vulcanization, form a dam or barrier to prevent the built in sealant from migrating towards the centerline during tire operation.
An optional shoulder divider strip 40 may also be applied to the axially outer surface 22 of the axially outer zones 10, 20. The divider strip together with the liner 6 and barrier 40 prevent migration of the sealant into the shoulder area of the tire.
Alternatively, as shown in
The thickness of the sealant in each of the zones 10, 15, 20 can vary greatly in an unvulcanized puncture sealant-containing tire. Generally, the thickness of the sealant composition layer may range from about 0.13 cm (0.05 inches) to about 1.9 cm (0.75 inches). In passenger and truck tires it is normally desired for the sealant composition layer to have a thickness of about 0.32 cm (0.125 inches).
After the unvulcanized pneumatic rubber tires of this invention are assembled they are vulcanized using a normal tire cure cycle. The tires of this invention can be cured over a wide temperature range depending somewhat upon the size of the tire and the degree of desired depolymerization of the butyl rubber as well as the thickness of the sealant layer itself) and sufficient to at least partially depolymerize said sealant precursor layer to the aforesaid storage modulus (G′) physical property.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be appreciated there is still in the art various changes and modifications may be made therein without departing from the spirit or scope of the invention.