Spring loaded tooling head and method for tire cord application

This invention relates generally to an improved apparatus for manufacturing a toroidal carcass ply for a tire and, more specifically, to an applicator head for direct application of a single end cord to an annular tire building surface.

Historically, the pneumatic tire has been fabricated as a laminate structure of generally toroidal shape having beads, a tread, belt reinforcement, and a carcass. The tire is made of rubber, fabric, and steel. The manufacturing technologies employed for the most part involved assembling the many tire components from flat strips or sheets of material. Each component is placed on a building drum and cut to length such that the ends of the component meet or overlap creating a splice.

In the first stage of assembly the prior art carcass will normally include one or more plies, and a pair of sidewalls, a pair of apexes, an innerliner (for a tubeless tire), a pair of chafers and perhaps a pair of gum shoulder strips. Annular bead cores can be added during this first stage of tire building and the plies can be turned around the bead cores to form the ply turnups. Additional components may be used or even replace some of those mentioned above.

This intermediate article of manufacture would be cylindrically formed at this point in the first stage of assembly. The cylindrical carcass is then expanded into a toroidal shape after completion of the first stage of tire building. Reinforcing belts and the tread are added to this intermediate article during a second stage of tire manufacture, which can occur using the same building drum or work station.

This form of manufacturing a tire from flat components that are then formed toroidally limits the ability of the tire to be produced in a most uniform fashion. As a result, an improved method and apparatus has been proposed, the method involving applying an elastomeric layer on a toroidal surface and placing and stitching one or more cords in continuous lengths onto the elastomeric layer in predetermined cord paths. The method further includes dispensing the one or more cords from spools and guiding the cord in a predetermined path as the cord is being dispensed. Preferably, each cord, pre-coated with rubber or not so coated, is held against the elastomeric layer after the cord is placed and stitched and then indexing the cord path to a next circumferential location forming a loop end by reversing the direction of the cord and releasing the held cord after the loop end is formed and the cord path direction is reversed. Preferably, the indexing of the toroidal surface establishes the cord pitch uniformly in discrete angular spacing at specific diameters.

The above method is performed using an apparatus for forming an annular toroidally shaped cord reinforced ply which has a toroidal mandrel, a cord dispenser, a device to guide the dispensed cords along predetermined paths, a device to place an elastomeric layer on the toroidal mandrel, a device to stitch the cords onto the elastomeric layer, and a device to hold the cords while loop ends are formed. The device to stitch the cords onto the elastomeric layer includes a bi-directional tooling head mounted to a tooling arm. A pair of roller members is mounted side by side at a remote end of the tooling head and defining a cord exiting opening therebetween. The arm moves the head across the curvature of a tire carcass built on a drum or core while the cord is fed through the exit opening between the rollers. The rollers stitch the cord against the annular surface as the cord is laid back and forth across the surface, the first roller engaging the cord along a first directional path and the second roller engaging the cord in a reversed opposite second directional path.

The toroidal mandrel is preferably rotatable about its axis and a means for rotating is provided which permits the mandrel to index circumferentially as the cord is placed in a predetermined cord path. The guide device preferably includes a multi axis robotic computer controlled system and a ply mechanism to permit the cord path to follow the contour of the mandrel including the concave and convex profiles.

While working well, certain challenges exist in the aforementioned proposed apparatus and method. For example, it would be desirable for the tooling head to maintain a constant optimal pressure against the annular surface. Excessive pressure can damage the cord or the underlying layer, resulting in a less than satisfactory cord layer in the finished tire. Excessive pressure can also break the cord, requiring a re-application of the cord layer and consequently detrimentally increasing manufacturing times. On the other hand, too little pressure on the cord may result in a less than optimal adherence of the cord to the underlying layer. Less than a proper level of adherence between the cord and the underlying layer may allow the cord to shift out of position during or after the cord laying procedure, resulting again in a cord layer that is defective in the finished tire.

Existing tooling heads, however, have proven less than adequate in maintaining constant optimal pressure against the annular core surface. Imperfections in the previously applied layers and the fixed spatial disposition of the rollers relative to the core surface result in a variable contact pressure exerted by the rollers against the annular surface. The consequence is a less controlled application of the cord against the annular surface.

A further drawback in proposed bi-directional tooling heads for laying a single end cord against an annular core surface is that such tooling heads are undesirably complicated and expensive to build and maintain. Such heads incorporate mechanical fingers and paddles to loop and pressure the cord into the ply compound as the head traverses the core surface. Controlling the pressure that such mechanisms exert upon the cord and annular surface, however, has proven problematic in view of the complexity of the mechanism itself and surface anomalies in the previously applied layer(s).

A need, accordingly, remains for an applicator head that is simple to construct, operationally reliable and efficient, and effective in bi-directional application of a single end cord to a tire carcass. Furthermore, a need exists for an applicator head that can effectively apply a tire cord at a constant optimal pressure against an annular core surface in order to adjust for surface layer(s) anomalies and thickness.

Pursuant to one aspect of the invention, a tooling head for bi-directional tire cord application to an annular surface has a nose block assembly slideably connected to a tooling head assembly. The nose block assembly moves reciprocally in an axial direction relative to the tooling head housing and includes a cord-engaging element. A cord engaging element moves with the nose block assembly in a forward and a reverse direction across the annular surface and is positioned to engage at least one cord against the annular surface in the forward and reverse directions. In accordance with the invention, a biasing element is provided to engage against the nose block assembly and bias the cord engaging element against the annular surface in the forward and reverse directions.

Pursuant to another aspect of the invention, the cord engaging element is represented by a plurality of rollers, at least one roller of the plurality of rollers engaging against the annular surface in the forward direction and disengaging from the annular surface in the reverse direction. Another aspect includes a tilting mechanism that tilts the nose block assembly between first and second angular positions while the cord engaging element moves respectively in the forward and reverse directions across the annular surface.

Pursuant to yet a further aspect of the invention, the tooling head assembly includes a chamber and the biasing element comprises a pneumatic intake in communication with the tooling head assembly chamber for directing pressurized air against the nose block assembly. The nose block assembly may thus maintain contact with the annular core surface at substantially a constant optimal pressure until the cord layer is completed by the tooling head traversing the annular surface in the forward and reverse directions.

According to another aspect of the invention, a method for bi-directional tire cord application to an annular surface is employed, comprising: mounting a tooling head for reciprocal movement in a forward and a reverse direction across the annular surface, the tooling head having a plurality of annular surface engaging roller components at a terminal end at the annular surface; feeding a length of tire cord through the tooling head to the terminal end of the tooling head; selectively routing the tire cord between at least one roller component and the annular surface as the tooling head moves across the annular surface; and biasing the at least one roller component against the annular surface as the tooling head moves across the annular surface. A method may further employed using a pneumatic spring for biasing the roller component against the annular surface at a substantially constant pressure as the tooling head moves across the annular surface.

“Aspect Ratio” means the ratio of a tire\'s section height to its section width.

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

“Bead” or “Bead Core” means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chaffers.

“Belt Structure” or “Reinforcing Belts” 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.