Rigid core in two portions for the manufacture of tires

Details Rigid core in two portions for the manufacture of tires Rigid core in two portions for the manufacture of tires

2000-08-10

2002-10-22

Mackey, James P. (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Reshaping, resizing or vulcanizing means for tire, tire...

Internal mold, form or support for toroid

C425S054000, C425S056000

Reexamination Certificate

active

06468062

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns the manufacture of tires. More particularly, the present invention relates to a substantially rigid core used as manufacturing support for a tire and as a means for molding the surface of the internal cavity of a tire.
The patent application EP 0 666 165 describes a manufacturing machine which employs such a core as manufacturing support for a tire. A core of this type is removed after the manufacture of each tire and is then reconstituted in order to act as a support for the subsequent manufacture of a further tire. A core of this type has to withstand numerous cycles of mounting and removal. The core has to be extremely robust in order to be able to guarantee a high level of geometric quality, and has to have highly durable geometric qualities over time, despite the considerable handling to which it is subjected. Furthermore, it is proposed in the patent application EP 0 666 165 that a rim be used as member for integrally connecting the various fractions of which a core of this type is necessarily composed.
The problem which arises is therefore to obtain a design of such a core which is sufficiently robust, without affecting, on the one hand, the ease of mounting and removal of this core and, also, without making the conveyance thereof from station to station on the manufacturing machine too complicated. Furthermore, a core of this type must be adapted to the exact form of each of the different tires to be manufactured. It is also desirable to have a certain degree of standardization in such a core so that the machine itself is as universal as possible. It is also expedient to be able to supply heat to the tire to be vulcanized through the core so that vulcanization can be as uniform and fast as possible. Finally, while being as robust as possible and while allowing excellent transmission of heat toward the tire to be vulcanized, a core of this type should be as light as possible in order to allow high acceleration and high speeds of conveyance from station to station.
The object of a rigid core of this type is to define, at least partially, a manufacturing form for the internal surface of a tire. It is known that a core of this type consists of a plurality of fractions to enable it to be extracted from the interior of a tire through the volume available inside the beads. It comprises a plurality of circumferentially adjacent fractions arranged side by side in contact with one another by their transverse faces. The term “transverse faces” denotes the faces running from one side of the core to the other. In the example described, these are plane faces which are parallel to the axis of the core, these characteristics not being limiting. Said transverse faces of at least one fraction converge radially at the exterior of the core. Such a core is shown in U.S. Pat. No. 4,895,692.
The invention proposes that each of these fractions be produced in two distinct portions which each meet their own requirements: an attachment portion and a main portion integrally connected to the attachment portion. The essential role of the main portion is the molding of the internal surface of the tire. The main portion therefore acts as a manufacturing form and molds the internal surface of a tire. The essential role of the attachment portion is to integrally connect the various fractions to a member for integrally connecting said various fractions constituting a core of this type.
Each of said fractions comprises a portion for attachment to a member for integrally connecting said various fractions, said attachment portion being arranged at the radially internal end of each of the fractions. Said attachment portion is essentially produced from a first material selected for its ability to withstand a large number of mounting and removal cycles. The attachment portion is designed to optimize the gripping of each of the fractions by the rim and by the various other handling members which may be provided on the grippers or on each of the stations for use of the core.
Each of said fractions also comprises a main portion integrally connected to said attachment portion, essentially produced from a second material which is different from the first material and is selected for its moldability and its good thermal conductivity. The main portion is integrally connected to said attachment portion, in other words is functionally unremovable. The main portion is produced so as to optimize the molding and vulcanization of the tire and also so as to be as economical as possible to produce because it is a specific part of each dimension of the tire whereas the attachment portion can be produced with identical plans and an identical design for a plurality of different tires.
It should be noted that it is very difficult to produce the crude blank of the tire with the exact form which will be imparted to it by vulcanization and molding. In particular, the lower portion of the bead can have a section which merely approaches the final section. The radially lowest portion of the bead can be located, in the crude state, at a radial level lower than that which will be obtained after molding. As a result, the shell extensions may scrape the radially internal portion of the tire beads somewhat during closure of the mold described in U.S. Pat. No. 4,895,692. In some cases, it can happen during this phase where the shell extensions scrape the still crude bead that they carry off a small portion of rubber which will be removed from the tire blank. This small portion of rubber is pushed back into the interior of the mold and is lost. It soils the mold and/or the press, thus reducing the possible duration of production between two mold and/or press cleaning operations. Furthermore, it risks causing subsequent defects in the appearance of the cured tires if this small portion of rubber pushed back into the interior of the mold is freed and returns into the mold cavity.
SUMMARY OF THE INVENTION
According to the present invention, this problem is solved by reserving the entire molding function to the main portion, no surface of the attachment portion having a molding function. In this case, an intermediate face is disposed in the direct extension, radially toward the smallest radii, in other words toward the interior, of the molding surface of the core. This intermediate face is either disposed in a plane perpendicular to the axis of rotation or forms a truncated cone with a very large angle, depending on the form and orientation of the molding portion. Therefore, if the radially lowest portion of the bead comes to a radial level lower than that of the finished tire, the flash possibly caused by the closure movement of the mold is simply pinched and not sheared off and remains attached to the tire. This prevents the above-described drawbacks.
Also and preferably, the joining line between the attachment portion and the main portion is accommodated in this intermediate surface, and this also prevents the appearance of a flash on the internal surface of the tire bead owing to the creep of the rubber between attachment portion and main portion. A further advantage of this disposition is that the attachment portion, or more specifically all the attachment portions of all the fractions, do not necessarily have to form a continuous surface as these attachment portions do not have a molding function.
Further details and advantages of the invention will be explained hereinafter with reference to the accompanying figures.


REFERENCES:
patent: 1221349 (1917-04-01), Merriman
patent: 1249033 (1917-12-01), Cobb
patent: 1303256 (1919-05-01), Clark et al.
patent: 1389892 (1921-09-01), Midgley, Sr.
patent: 1810072 (1931-06-01), Denmire
patent: 1903458 (1933-04-01), Johnson
patent: 4063861 (1977-12-01), Schmidt et al.
patent: 4083672 (1978-04-01), Vaishnav
patent: 4301850 (1981-11-01), Schneider et al.
patent: 4877468 (1989-10-01), Siegenthaler
patent: 4895692 (1990-01-01), Laurent et al.

Affiliated with

Also associated with

Rating

Rigid core in two portions for the manufacture of tires does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rigid core in two portions for the manufacture of tires, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rigid core in two portions for the manufacture of tires will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2997242