Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se – Utilizing surface to be reproduced as an impression pattern
Reexamination Certificate
1997-07-30
2001-05-01
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
Utilizing surface to be reproduced as an impression pattern
C264S313000, C264S317000, C264S326000, C264S501000, C264SDIG004, C264S331130, C249S061000
Reexamination Certificate
active
06224808
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a destructible core for the manufacture of hollow objects of various shapes, in particular hollow parts which could not be removed from a one-piece metallic mold. In particular, the invention proposes a core of approximately toroidal shape, defining the inner cavity of a tire, for the manufacture of a tire having a shape identical or very close to the shape established by the vulcanization.
Such cores have already been proposed in the prior art, in particular in the field of tires. Mention may be made of rigid cores of metal which are divided into several parts so that they can be extracted from the inside of the tire after the tire has been vulcanized. Mention may also be made of U.S. patent application Ser. No. 08/785,422 which describes a device comprising a reinforced rubber membrane which can serve as a rigid core during the assembling of a rubber tire from its basic components and which can be withdrawn from the tire by folding said reinforced membrane.
All of these devices provide solutions which are technically satisfactory. However, their manufacture is rather lengthy and expensive. The object of the present invention is to propose means for providing a substantially rigid core, which lends itself well to the manufacture of tires, but which may have broader applications.
SUMMARY OF THE INVENTION
The invention relates to a method of manufacturing an object comprising, during each manufacturing cycle, the steps of:
creating a cavity of predetermined volume and shape by means, on the one hand, of a new contribution of material forming a membrane which is placed on the molding surface of a first mold, said molding surface having an opening, and by means, on the other hand, of a support which closes said opening and is in contact with said membrane over the entire periphery of the opening, in order to define a closed space within said support and said membrane,
filling the entire volume of said cavity to overflow with a fluidizable solid material;
making said fluidizable material rigid and opening the mold in order to release a rigid core which is integral with said support containing said fluidizable material which has been made rigid, while maintaining the said core by the support, and of using said core to manufacture an object, the core defining a so-called inner surface of said object;
making said fluidizable material fluid and extracting it in order to destroy the core and to recover said material for the manufacture of a following object.
By way of example of a fluidizable material, mention may be made of a pulverulent material which is made rigid by creating a vacuum in said space in order to apply the membrane against said material and which is made fluid by eliminating the vacuum.
In the carrying out of the method proposed, said membrane is applied against said material under the effect of a vacuum created in said closed space, which makes said fluidizable material rigid, and said material is extracted after having broken said vacuum, which makes said material fluid again. The principle used consists in imprisoning, in a very thin and stretchable membrane, a filling material having for instance the form of a fine sand and then forming a vacuum in order to obtain a rigid form. This means that the form should be sufficiently coherent, sufficiently firm to act as a manufacturing support as explained hereunder. Balls of small diameter, of for instance between 0.1 and 0.5 mm, constitute a suitable filling material. For example, hollow or solid glass balls of a diameter of about 0.2 mm may be used. Such a material may very easily be made sufficiently fluid to facilitate the flow thereof, for instance by judiciously selecting and/or conditioning the fluid in which said material is bathed.
A suitable membrane is formed, for instance, of a plastic film. One type of film which is suitable is, for instance, a sheet of Nylon of a thickness of 50 micrometers. Of course, the precise selection of the material constituting the membrane depends on the application intended. The membrane is said to be stretchable because it can adapt itself to the shape which it is desired to impart to the core. The stretching which it undergoes may be result in permanent deformation. In order to place the membrane on the molding surface of the first mold, one can proceed in the following manner: unwind a sheet of stretchable material constituting said membrane, cover the surface of said support and fasten said membrane over the entire periphery thereof, which defines a closed space between support and membrane, close said first mold around the assembly consisting of support and membrane in order to create said cavity of predetermined volume and shape and, from the side of said support on which the membrane has been mounted, apply the membrane against the wall of said first mold. The membrane can be stretched until it is brought in contact with the first mold after the closing of the first mold and after filling said volume by subjecting said closed space to an increase in pressure. The stretching can be facilitated, for instance, by an increase in temperature.
In the case of the application to rubber tires, the film selected must be compatible with use at the temperature of vulcanization of the tire. Further, the rubber constituting the inner skin of the tire must be able to adhere sufficiently on the core while it is deposited, in accordance with the method of depositing selected. As example of such a method, mention may be made, for instance, of the winding of ribbons of raw rubber in suitable manner on and around the core.
One advantage of the invention is that it is possible to obtain a core within a very short time after the designer of the object to be manufactured has defined the shape thereof. In the case of tires, it is very easy to produce the first mold on a lathe. In the more particular case of tires in which the ratio of the height of the sidewall divided by the diameter at the seat is rather great, the invention makes it possible to produce a core which can very easily be used for such tires since the destruction of the core does not raise any particular problem, in contrast to the difficulty of removing from the mold a rigid core formed of several heavy parts by passing the heavy parts through the small space available within the tire.
Another advantage of the invention is to propose the means for creating a core on which a pneumatic tire or a non-inflated or non-pneumatic elastic solid tire can be built in its final shape. As to the support, after the steps of the method of manufacture which have been mentioned above, the object and the membrane can either be separated from said support in order to use said support again in a subsequent manufacturing cycle of an object (the support forms part of a machine) or else the support constitutes, after the manufacture of the object, an integral part thereof and, in this case, the support is renewed upon each manufacture of said object. For example, it is made on the same installation. In this case, there is produced a pneumatic tire fastened permanently on its rim, or else a solid tire attached permanently to its rim or to any member (serving as support in the present invention) which permits mechanical attachment to a wheel or to a rotary member, while being able to obtain a closed pneumatic cavity upon the manufacture of the pneumatic or solid tire.
In its application to a pneumatic tire, the support is, for instance, a rim on the radially outer side of which said membrane is mounted. The edges of the membrane are fastened over the entire periphery of said rim in two annular lateral anchoring zones so as to define said closed space on the radially outer side of said rim, between the rim and the membrane. The core obtained is toroidal. It is used as inner core around which a pneumatic tire is manufactured and molded. The molding of the so-called outer surface of said tire is obtained by means of a second mold. When the molding of the tire has been completed, the said second mol
Essinger Olivier
Laurent Daniel
Baker & Botts LLP
Conception et Developpement - Michelin S.A.
McDowell Suzanne E.
Tentoni Leo B.
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