WO2001017757A1

WO2001017757A1 - Method and apparatus for manufacturing a tire carcass

Info

Publication number: WO2001017757A1
Application number: PCT/US1999/020738
Authority: WO
Inventors: Frederick Forbes Vannan, Jr.; William Allen Rex; Brian Joseph Wilson; Kevin James Pyle; Scott Richard Harshbarger
Original assignee: The Goodyear Tire & Rubber Company
Priority date: 1999-09-09
Filing date: 1999-09-09
Publication date: 2001-03-15
Also published as: AU6032099A

Abstract

An apparatus (4) and method of manufacturing a tire carcass (20) is disclosed. The apparatus (4) includes a rubber carcass forming and shaping mold (60) having a first portion (64) and a second portion (65) and a solid core (62), the first (64) is movable while the core (62) includes an air fluid nozzle (70) which when pressurized, releases the carcass (20) from the core (62). The opening and closing of the first (64) in combination with the pressurized core (62) provide a novel method of removing the molded carcass (20) automatically from the mold (60).

Description

METHOD AND APPARATUS FOR MANUFACTURING A TIRE CARCASS Technical Field

This invention relates to an apparatus for forming a precured non-cord reinforced tire carcass and a novel method of manufacture. Related Patent Applications

This application is related to a co-pending PCT application entitled A PRECURED NON- CORD REINFORCED CARCASS (Attorney Docket No. DN1999-065-PCT ffled concurrently with the present application). Background of the Invention

Generally the pneumatic tire has been produced by forming a toroidaUy-shaped carcass having one or more layers of plies reinforced by cords. These cords are generally arranged in a paralleled orientation within each layer. Bias plied tires have the cords oriented in equal but opposite directions in each adjacent layer or ply. Radial ply tires have the cords oriented generally about 90° relative to the tire's centeiplane.

The carcasses have a variety of other components, each designed for a specific function or task. The combination of tire components, after undergoing a procedure commonly referred to as "vulcanization" , results in a composite structure recognized in the art as a pneumatic tire.

Ideally, tire engineers strive to achieve tire performance objectives while also reducing the cost. This can be accomplished by either processing improvements or material changes.

Modern tire factories are and continue to evolve into a highly capital intensive industry. The tire carcass of the present invention greatly simplifies the manufacture of tires resulting in huge opportunities to minimize cost.

The present invention can produce a tire carcass that is a single component formed by a single material that is vulcanized as it is being formed.

The preferred embodiment invention can also form an integral tread portion such that the article of manufacture can be the complete tire requiring no other components other than the rim to which the tire is to be mounted.

The concept, as described above, is best performed by selecting a unique elastomeric rubber alloy material for the carcass and by injection or compression transfer molding that alloy to form the tire carcass or tire. Unlike any of the prior art tires used in the toy industry. This tire preferably has a nominal rim diameter of about 6 inches (15 cm) or greater and is designed to meet the performance criteria of conventional tires.

The resultant tire carcass is suitable for a variety of uses in applications such as, but not limited to, passenger or light truck vehicles, lawn and garden tractors and mowers, golf cart tires and other all-terrain vehicle tires.

The concept of a single compound for forming a tire is well known and common in such areas as toys wherein plastic or rubber tires are made from a single material. Unlike these small reduced scale concepts, the present application is a full scale tire carcass subject to real use conditions. Heretofore, materials to make such a tire have been unavailable. Recent developments in the field of rubber compounding technology has resulted in rubber compositions known as rubber alloys. These alloys have thermoplastic side chains grafted thereto, the thermoplastic being selected from the groups consisting of, but not limited to, nylons, polyesters, and polyphenylene oxides. These alloys can be compounded extremely tough and having unique physical properties that enable the carcass to be manufactured from a single compound.

Prior attempts to make non-reinforced tires have been disclosed in U.S. Patent Nos. 4,061,171 and 4,230,169; both patents having Jacques Boileau of Michelin as the inventor. Both patents disclose the need for additional rubber mass in either the bead area or in the tread sidewall areas. Neither invention disclose the use of alloy type rubber materials for the forming of a tire carcass. Such materials were not known in the mid-1970' s and, as a result, such tires were never commercialized.

This recent breakthrough in compounding an alloy rubber enables the mold and method of manufacturing to be greatly simplified. The following discloses the apparatus and a preferred method of manufacturing the article. Disclosure of the Invention

Summary of the Invention

A method of forming a precured non-cord reinforced carcass (20) in a mold (60) having a movable first portion (64), a fixed second portion (65), and a core (62) having a pressure nozzle (70) is disclosed. The method has the steps of plasticizing a rubber material (2) and feeding a flow of the plastic rubber material (2) across a disk-shaped cavity surrounded by an annular gate (66) of reduced cross-sectional thickness into a carcass-forming cavity (100); thus, forming the precured non-cord reinforced carcass (20); curing the carcass (20) under heat and pressure; initiating the opening of the mold (60); wherein the first portion (64) is moved a sufficient distance to clear the formed carcass (20); moving the core (62) having the formed precured carcass (20) attached, thereby clearing both first and second portions (64, 65) supplying air pressure to the nozzle (70) of the core (62), thereby supplying air between the formed disk (40) and carcass (20) and the core (62), thereby inflating the formed carcass (20) and disk

(40); restraining the inflated carcass (20) and disk (40) by controlling the distance between the first portion (64) of the mold (60) and the core (62), moving the first portion (64) from the core (62) as the restrained inflated carcass (20) and disk (40) stretch and slide over the core

(62). The method further can include the step of stopping the flow of air through the nozzle

(70) of the core (62) after the carcass (20) begins to contract from a maximum stretch but before the contracting carcass (20) slides from the core (62).

The step of stopping the movement of the first portion (64) can occur when the carcass

(20) contracts sufficiently to slide off the core (62), at which point the removal of the carcass (20) and disk (40) from the mold (60) can occur. Subsequently, the disk (40) can be removed from the carcass (20).

The apparatus (4) for forming a precured non-cord reinforced carcass has a frame (6), a mold (60) attached to the frame (6). The mold (60) has a movable first portion (64), a fixed second portion (65) and a core (62). The core (62) in combination with the first portion (64) and second portion (65) forms a carcass-forming cavity (100).

The apparatus (4) is characterized by the mold (60) having one central gate (66) in the first portion (64), the central disk forming gate (66) being bounded by an annular gate (67) having a reduced cross-sectional thickness for forming an annular tear ring (42), the annular tear ring (42) is connected to a bead seat (24) of one of the bead portions (22) of the carcass (20) forming a cavity (66) and an air pressure nozzle for supplying air between the formed carcass (20) and the solid core (62).

The apparatus (4) can employ sensors (72) for determining when to stop the air flow through the nozzle (70).

The means (80) for moving the first (64) of the mold (60) can be one or more hydraulic cylinders (82).

Brief Description of Drawings

FIGURE 1 is a cross-sectional view of the precured non-cord reinforced carcass (20). FIGURE 2 is a cross-sectional view of the precured non-cord reinforced carcass (20) with a tread (12) and belt reinforcing (36) structure applied.

FIGURE 3 is a preferred embodiment of the invention wherein a tire (10) is shown in cross-section, the tire (10) has the tread and non-cord reinforced carcass (20) simultaneously formed.

FIGURE 4 is a schematic view of the carcass (20) being formed in an injection molding apparatus (4) preferably having a solid core mold (60).

FIGURE 5A, 5B and 5C are schematic views of the carcass (20) being removed from the mold (60). FIGURE 6 is a schematic view of the apparatus (4) and the mold (60).

Definitions

"Axial" and "axially" means the lines or directions that are parallel to the axis of rotation of the tire.

"Bead core" means that part of the tire comprising an annular tensile member to fit in the bead portion of the carcass securing the carcass to the design rim.

"Belt reinforcing structure" means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 27° with respect to the equatorial plane of the tire. "Carcass" or "Casing" means the tire structure apart from the belt structure and the tread.

"Circumferential" means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.

"Cord" means one of the reinforcement filaments, cables or strands of which the plies in the prior art tire are comprised. "Equatorial Plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

"Innerliner and 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 continuous layer of rubber-coated parallel cords. "Precure" or "Precured", as used herein, means the rubber material (2) is partially or completely vulcanized. "Radial" and "radially" mean directions radially toward or away from the axis of rotation 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.

"Section Height" (SH) means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.

"Section Width" (SW) means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.

"Shoulder" means the upper portion of sidewall just below the tread edge.

"Sidewall" means that elastomeric portion of a tire between the tread and the bead.

"Tread" means a rubber component which when integrally formed with or bonded to a tire carcass includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.

Detailed Description of the Invention

With reference to FIGURE 1, a precured non-cord reinforced tire carcass (20) is shown. As illustrated, the tire carcass (20) has a nominal rim direction of at least 6.0 inches (15 cm). The carcass (20) has a pair of sidewall portions (16, 18) and a central crown portion (14).

As shown, one sidewall portion (16, 18) extends from each bead portion (22) radially outwardly. The central crown portion (14) extends from and between each radially outer portion of the sidewall portions (16, 18).

The combination of the bead portions (22), sidewall portions (16, 18) and crown portions (14) define the peripheral boundary of an internal chamber (15) of the tire (10) when mounted on a rim (30).

The precured non-cord reinforced tire carcass (20) has the bead portions (22) sidewall portions (16, 18) and central crown portions (14) being of the same elastomeric rubber material

(2) wherein the elastomeric rubber material (2) is a rubber alloy of rubber and one or more thermoplastic materials having a modulus at 100% of at least 5.0 MPa and a percent elongation of at least 100% but less than 400%, preferably. As illustrated in FIGURE 2, the carcass (20) may have a belt reinforcing structure (36) placed radially outward of the carcass (20). The belt reinforcing structure (36) preferably has two or more cord reinforcing layers (50, 51). Radially outward of the belts (36) may be an optional fabric overlay (59) reinforced with cords (70) and a tread (12), the combination forming a tire (10).

As shown in FIGURE 3, the bead portion (22) has a radially inner bead seat (24) which extends generally axially outwardly. The rim (30) that the tire carcass (20) is mounted onto may have a pair of annular bead cores or rings (26) that fit radially outwardly of the bead seats (24). These bead cores or rings (26) clamp the tire carcass (20) rigidly to the rim (30). The bead core or rings (26) can be integrally formed as part of the tire carcass (20) or, alternatively and preferably, may be separate pieces as shown. When one or both of the bead cores (26) are not part of carcass (20) as it is formed, the use of a solid core mold (60) is feasible. This greatly simplifies the tooling cost and enables the carcass (20) to be stretched over a solid mold core (62) during manufacture. With reference to FIGURES 4, 5A, 5B and 5C, the preferred method to mold the tire carcass (20) is illustrated.

The tire carcass (20) is formed by plasticizing the alloy material (2) under heat and pressure and passing the rubber through a central gate (66) that feeds annularly from a first portion (64) of the tire mold (60). The central gate (66) creates a round disk (40) with a shallow annular tear ring (42) at the first bead portion (22) as shown. The rubber material (2) then flows through the bead portion (22) and the sidewalls (16) through the central crown region (14) and fills the opposite sidewall (18) and bead portion (22). After a short cure time, the mold (60) is opened as shown in FIGURE 5A; the first portion (64) moves relative to a fixed second portion (65) of the mold (60) and the core (62) having the formed carcass (20) attached thereto moves relative to the second portion (65); thus, clearing the part or carcass from each mold portion (64, 65). It is to be appreciated that the first portion (64) may be fixed while the second portion (65) is movable as an alternative. In that alternative, the disk (40) and the central gate (66) must be fed through the movable second portion (65). Air pressure is sent under the round disk (40) of the central gate (66). As the air enters the carcass (20) and the disk (40) expands, the expansion creates a release of the carcass (20) from the solid core (62) as shown in FIGURE 5B. The first portion (64) of the mold (60) is positioned close to the expanding carcass (20) so that as the carcass (20) expands on the gate side the carcass (20) contacts the first portion (64) of the mold (60) restraining the movement of the carcass (20). Then, the first portion (64) of the mold is further moved away from the core (62). As this further movement occurs, the first portion (64) restrains the carcass (20) as the second side of the carcass (20) along the sidewall (18) and bead portion (22) radially expands sliding as it expands over the core (62). Once the bead portion (22) is over halfway stretched on the core (62) , the expanded bead portion (22) starts to contract as it passes over the rest of the core (62) and, accordingly, the air pressure can be cut off as the freshly-formed carcass (20) automatically releases itself from the core (62) as it contracts to an unloaded, non- stretched condition.

The amount of stretch required of the bead portion (22) is at least an additional 100% relative to the relaxed state. The fact that the carcass material (2) is still hot, generally at a temperature of 100°C to 150°C, in combination with the specifically formulated alloy rubber material (2) insures that the bead portion (22) can be stretched without exhibiting surface fractures. Heretofore, common rubbers employed in the manner described above had a wide range of surface fractures in the bead seat (24).

To compensate for this problem, an alloy material (2) having specifically selected physical properties as described below has been developed.

This invention specifically relates to a process for manufacturing a carcass (20) which comprises (1) using an elastomeric rubber material (2); wherein the composition of the elastomeric rubber material is comprised of (a) an alloy comprised of (i) elastomeric rubber having thermoplastic side chains grafted thereto, and (ii) dispersed thermoplastic; wherein the thermoplastic is selected from the group consisting of, but not limited to, nylons, polyesters, and polyphenylene oxides, (b) an elastomeric rubber material, (c) carbon black, (d) at least one curative, (e) zinc oxide, (f) a processing oil, and (g) stearic acid; (2) molding the carcass (20) into the geometric form desired for the carcass (20), and (3) curing the rubber material (2) at a temperature within the range of 130°C to 210°C to produce the carcass (20). The subject invention also discloses a process for manufacturing a carcass (20) which comprises injection or transfer molding the elastomeric rubber material (2) into the desired geometric form at a temperature which is within the range of 130°C to 210°C; wherein the elastomeric rubber material (2) is comprised of (a) a rubber alloy comprised of (i) elastomeric rubber material, having thermoplastic side chains grafted thereto, and (ii) dispersed thermoplastic wherein the thermoplastic is selected from the group consisting of, but not limited to, nylons, polyesters, and polyphenylene oxides, (b) elastomeric rubber material, (c) carbon black, (d) at least one curative, (e) zinc oxide, (f) a processing oil, and (g) stearic acid, and (2) curing the rubber composition at a temperature within the range of 130°C to 210°C to produce the carcass (20).

The method of molding, as illustrated in FIGURES 5A and 5B and 5C, creates or forms the carcass (20) with one side formed with a disk portion (40) and preferably an annular tear ring (42) radially inward of the bead portion (22). The interface between the disk portion (40) and the bead portion (22) is an annular gate (42) of reduced cross-section. These components effectively create a rubber seal on one side of the carcass (20) formed by the cavity defined by the first mold portion (64) and the core (62).

On the opposite side of the carcass (20), the bead portion (22) is simply ended at the bead seat surface (24) creating an opening for rim mounting.

Accordingly, when air is injected through the nozzle it creates a domed air pocket between the rubber disk portion (40) and the core (62). As more air is introduced, the disk (40) contacts the first mold portion (64) preventing further outward expansion. Once the carcass (20) is so restrained, the introduction of more air tends to separate the remaining portion of the carcass (20) from the core (62). As this is accomphshed, the static friction or adhesion onto the core (62) is virtually completely eliminated. The air creates an air cushion. The force applied to the portion of the carcass (20) along the interior sidewall (16) and the disk (40) must be greater than the amount of force required to stretch the second bead portion (24) over the core (62). Assuming this relationship is satisfied, the carcass (20) will automatically slip over the core (62) and release from the core (62) as the first mold portion (64) is moved away from the core (62).

In practice, it has been determined that the carcass (20) must still be sufficiently warm when the mold (60) opens. The warm, rubber alloy material (2) is more stretchable at lower forces, this effectively facilitates the dilation of the second bead portion (22) over the core (62). Once the carcass (20) cools to room temperature, the percentage that the bead portion (22) can stretch without creating surface fractures in the bead seat area is dramatically reduced.

As can be seen, the design of the carcass bead portion (22), the use of a closed or sealed side of the carcass (20) having a disk (40) while the opposite side is free to expand in the absence of bead core (26), the injection of air pressure to free the molded carcass (20) from the core (62) and create a force which is sufficient to make the disk (40) side of the carcass (20) effectively expand as the rest of the carcass (20) is stretched over the core (62) as the first portion (64) of the mold (60) constrains the movement of the carcass (20) in a controlled manner are the features that enable the carcass (20) to be manufactured in such a novel manner. Once removed, the carcass (20) can be trimmed at the annular tear ring (42) and the disk (40) discarded.

In the preferred embodiment tire (10), the carcass (20) and tread (12) can be formed as a single part in the mold (60). This results in the simultaneous forming of the entire tire (10). This concept is useful in the ATV tires and golf and lawn type products.

The apparatus (4) for forming the carcass (20), as illustrated in FIGURE 6, has a frame (6), a mold (60 attached in a manner to slide relative to the frame (6), a means (80) for sliding or moving the mold, and a means (90) for injecting a volume of plasticized rubber material (2) into a carcass-forming cavity (100) of the mold (60). The mold (60) has a movable first mold portion (64) and a fixed second mold portion (65) and a core (62). The core (62) in combination with the first mold portion (64) and the second mold portion (65) and a core (62) form a carcass-forming cavity (100).

The means (80) for moving the first portion (64) or the second portion (65) of the mold (60) preferably is one or more hydraulic cylinders (82). The means (81) for moving the core (62) is one or more hydraulic cylinders (84). The movement of the core (62) is controlled by a limit switch (99) as shown.

The means (90) for injection the volume of plasticized rubber material (2) in to the carcass-forming cavity (100) preferably is part of an injection or compression molding press (4).

The mold (60) has one central gate for forming a disk (40) and an annular tear ring (42). The annular tear ring (42) has a reduced cross-section thickness and is connected to one bead seat (24) forming portion of the carcass-forming cavity (100).

An air pressure nozzle (70) is provided which supplies air between the formed carcass (20) and the core (62).

The apparatus (4) further can have sensors (72) for determining when to stop the air flow from the nozzle (70), the sensor (72) is actuated after the first mold portion (64) is moved a predetermined distance.

Claims

1. A method of forming an elastomeric precured non-cord reinforced tire carcass (20) the method characterized by the steps of: molding elastomeric material (2) into a toroidally-shaped tire carcass (20) having a first and second annular bead portions (22), the first bead portion (22) being integrally formed with a radially inner disk (40) creating a sealed first side of the carcass (20).

2. The method of claim 1 wherein the step of molding a toroidally-shaped tire carcass (20) includes providing an annular tear (42) of reduced cross-section between the first bead portion (22) and the radially inner disk (40).

3. The method of claim 1 is further characterized by the steps of: curing the toroidally-shaped tire carcass (20), and opening the mold while supplying air pressure between the sealed first side of the carcass (20) and a core (62), thereby, releasing the carcass (20) from the core (62).

4. The method of claim 3 wherein the step of supplying air pressure expands the sealed first side of the carcass (20) and simultaneously stretches the second bead portion (22) over the core

(62).

5. The method of claim 4 wherein the step of opening the mold (60) includes the step of restraining the carcass (20) by a controlled movement of a first portion (64) of the mold away from the core (62).

6. A method of forming a precured non-cord reinforced carcass (20) in a mold (60) having a movable first portion (64), a fixed second portion (65) and a core (62) having a pressure nozzle (70) the method having the steps of: plasticizing a rubber material (2) and feeding a flow of the plasticized rubber material (2) across a central gate (66) forming a disk (40) surrounded by an annular tear ring (42) of reduced cross-sectional thickness into a carcass-forming cavity (100), thus, forming a tire carcass (20); curing the carcass (20) under heat and pressure; initiating the opening of the first portion (64), the first portion (64) being moved a sufficient distance to clear the core (62) and the formed carcass (20); moving the core (62) a distance sufficient to clear the core (62) and formed carcass

(20) from the second portion (65); pressurizing the nozzle (70) of the core (62), thereby, supplying air between the formed disk (40) and carcass (20) and the core (62), thereby, inflating the formed carcass (20) and disk (40); restraining the inflated carcass (20) and disk (40) by controlling the distance between the first portion (64) of the mold (60) and the core (62); moving the first portion (64) away from the core (62) as the restrained inflated carcass (20) and disk (40) stretch sliding over the core (62).

7. The method of claim 6 further comprising the steps of: stopping the flow of air through the nozzle (70) of the core (62) after the carcass (20) begins to contract from a maximum stretch but before the contracting carcass (20) slides from the core (62).

8. The method of claim 7 further comprises the steps of: stopping the movement of the first mold portion (64) when the carcass (20) contracts off the core (62); and removing the carcass (20) and disk (40) from the mold (60).

9. The method of claim 8 further comprises the steps of: removing the disk (40) from the carcass (20).

10. An apparatus (4) for forming a precured non-cord reinforced carcass (20) having; a frame (6); a mold (60) being attached to the frame (6), the mold (60) having a first portion

(64), a second portion (65) and a core (62); the core (62) in combination with the first portion (64) and a second portion (65) forms a carcass-forming cavity (100); a means (80) for moving the first or second portions (64, 65) relative to the core (62); a means (81) for moving the core (62) relative to the first and second portions

(64, 65); a means (90) for injecting a volume of plasticized rubber material (2) into the carcass-forming cavity (100); the apparatus characterized by the mold (60) having one central gate (66) for forming a disk (40) and an annular tear ring (42) in the first portion (64), the disk (40) being bound by an annular tear ring (42), the annular tear ring (42) having a reduced cross-sectional thickness and being connected to a bead seat (24) forming portions of the carcass-forming cavity (100) and an air pressure nozzle (70) for supplying air between the formed carcass (20) and the core (62).

11. The apparatus of claim 10 further characterized by a sensor (72) for determining when to stop the air flow from the nozzle (70), the sensor (72) being actuated after the first portion (64) is moved a predetermined distance.

12. The apparatus of claim 10 wherein the means (80) for moving the first portion (64) is one or more hydraulic cylinders (82).

13. The apparatus of claim 10 wherein the means (90) for injecting a volume of plasticized rubber material (2) includes an injection molding press (4).