Plastic article or earthenware shaping or treating: apparatus – Reshaping – resizing or vulcanizing means for tire – tire... – Toroidal or annular female shaping means and coacting means...
Reexamination Certificate
1999-07-15
2001-05-29
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Reshaping, resizing or vulcanizing means for tire, tire...
Toroidal or annular female shaping means and coacting means...
C425S043000, C425S046000, C425S048000, C425S054000, C425S058000
Reexamination Certificate
active
06238193
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the molding of tires. In particular, it pertains to the molding of a tire comprising two beads of special shape, requiring an undercut molding of a portion in the axially and radially inner zone of the bead. Reference is made here to a zone undercut in relation to the relative motion between the tire and the molding parts normally used to mold the axially outer surface of the side and bead of a tire.
In the prior art, means are known for accomplishing the undercut molding of a portion on a tire bead. For example, U.S. Pat. No. 5,129,802 proposes using two counter-molding rings for the axially and radially inner portion of the bead, said rings being continuous. In such a case, the counter-molding rings must be introduced into the interior of the tire. For this, it is necessary to deform the raw blank of a tire by ovalizing at least one of the beads, so that the said bead can be made to pass beyond the counter-molding ring. Rings for molding the radially and axially inner portion of a bead have also been described in connection with so-called membrane-less vulcanizing presses. See, for example, U.S. Pat. No. 4,236,883, which discloses such rings, in this instance made in several segments circumferentially adjacent in molding position. The patent cited above describes a mechanism occupying integrally the inner volume of the press, so that the necessary movements can be imparted to the several ring segments in order for said segments to accommodate a closing or opening movement in sequence. By a “movement in sequence” is meant that, from a configuration in which the mold is open, the segments do not all go to their molding position at the same time. A first group is brought to its final molding position, then the segments of a second group are inserted between segments of the first group to make a continuous ring.
SUMMARY OF THE INVENTION
The object of the present invention is to propose a means serving to mold undercut zones, in the sense of this expression as given above, on the beads of a tire, without unduly increasing the cost of a mold per tire.
The invention arises from the realization that if the diameters of the tire beads are sufficiently different, it is possible to use a continuous counter-molding ring on one side, in other words, a one-piece ring. The beads of larger diameter can pass over the counter-molding ring of the bead of smaller diameter without need for any deformation. This is favorable to the quality of molding and to the economy of the process. It is indeed difficult, and impairs tire quality, to induce deformations in the raw tire casing. The invention avoids, or at least reduces dramatically, the need for any ovalizing deformation at the stage of the raw blank. For at this stage, the raw rubber does not as yet have significant mechanical strength to readily withstand the phases of ovalizing deformation and manipulations to cross a continuous rigid ring whose outside diameter is greater than the inside diameter of the beads to be vulcanized.
For the other bead, use may be made of a counter-molding ring split into several segments. The invention also proposes combining the use of counter-molding rings, of which one is continuous and the other split, with the use of a flexible membrane to mold the portion of the inner tire cavity between the counter-molding rings. The asymmetry of the mold so proposed renders it easier to accommodate, inside the press, the mechanism required to control the counter-molding ring split into several segments and the mechanism required to move the vulcanizing membrane.
The mold, according to the invention, for a tire having a tread, two sides, and two nonsymmetrical beads, &PHgr;
0
being the least diameter of the tire area at the bead of smaller diameter, &PHgr;
2
being the least diameter of the tire area at the bead of greater diameter, comprises:
two shells for molding, respectively, the outer surface of each side and the outer portion of each bead up to a radially inner limit where the diameter of the tire area is &PHgr;
0
and &PHgr;
2
, respectively;
a continuous counter-molding ring to mold the bead of smaller diameter from the said radially inner limit where the diameter of the tire area is &PHgr;
0
to an axially inner limit of diameter &PHgr;
1
, where &PHgr;
1
is smaller than &PHgr;
2
and where &PHgr;
1
is greater than &PHgr;
0
.
Preferably, the mold further comprises a split counter-molding ring to mold the bead of greater diameter from said radially inner limit where the diameter of the tire area is &PHgr;
2
to an axially inner limit of diameter &PHgr;
3
, said split ring comprising a plurality of retractable segments, adjacent in molding position.
Advantageously, the mold according to the invention comprises a flexible membrane to mold the inner surface of the tire in the portion of the inner cavity of the tire between the limit of diameter &PHgr;
1
and the limit of diameter &PHgr;
3
. Of course, for the portion molding the outer surface of the tire beyond the beads, any suitable type of mold may be used. For example, shells can be used for molding of the sidewalls alone, whereas use is made of a set of radially movable sectors to mold the tread. Those skilled in the art are acquainted with sector molds. It is likewise possible to use a two-part mold. In this type of mold, each half of the tread is molded by a molding portion integral with one of the shells. It is likewise possible to use a two-part mold in which the portion molding the tread is itself made up of sectors.
In fact, the invention proposes means for molding the inner surface of the tire as far as the beads, including at least partially the radially inner portion of the beads. This is especially serviceable when the said surface has a special shape, in particular undercut in relation to a reference direction parallel to the axis. The molding of the outer surface of the tire is not a concern of the present invention. It is believed that any suitable type of mold can be used.
The invention likewise proposes a tire vulcanizing press comprising a mechanism serving to impart to a counter-molding ring in several parts all the motions required, without adding any controls besides those normally available on a vulcanizing press. The invention proposes a press of membrane type, so arranged and adapted that the motion of the lower membrane plate relative to the lower frame suffices also to drive the motion of all the segments of the counter-molding ring.
The press according to the invention receives a tire mold having a centerline corresponding to the axis of rotation of said tire, said mold comprising:
two shells to mold the outer surface of a sidewall and to mold the outer portion of one of the beads up to a radially inner limit where the diameter of the tire area is a minimum;
at least one split counter-molding ring to mold the surface of a bead beyond the said limit and on the axially inner side, said split counter-molding ring being made up of first segments and second segments, said first and second segments being adjacent in molding position;
a membrane molding the inside of the tire.
The press according to the invention further comprises:
a lower frame to receive one of the shells;
a movable frame to receive the other shell;
means of driving the relative approach and withdrawal of said lower frame and movable frame toward and away from each other;
a lower membrane plate;
means for imparting relative motion between the lower membrane plate and the lower frame;
first means to receive first segments and second means to receive second segments, the set of first and second segments constituting the said split counter-molding ring;
a mechanism to move the first and second segments, said moving mechanism being actuated by the relative motion of the lower plate with respect to the lower frame, and effecting the movement in successive sequences of the first segments in a first sequence, and of the second segments in a second sequence, so as to bring said segments of the counter-molding ring into molding
Baker & Botts L.L.P.
Del Sole Joseph S.
Michelin Recherche ET Technique S.A.
Pyon Harold
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