Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Shaping against interior of a forming surface by rotation of...
Reexamination Certificate
1998-09-04
2001-05-01
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Shaping against interior of a forming surface by rotation of...
C264S521000, C264S523000, C264S537000, C264S905000, C264S906000, C264S535000, C264S530000, C425S522000, C425S182000, C425S195000
Reexamination Certificate
active
06224817
ABSTRACT:
This invention is about refinements added to the process of setup and manufacturing of thermoplastic containers, such as bottles, that have a curved central section in the bottom, from rough shapes that too have a curved central section in the bottom with an inward convexity, the process containing at least a heating period of at least the body of the rough shape to bring the thermoplastic material to its softening temperature, a step during which the rough shape is positioned in a finishing mold designed to achieve the finished container, this finishing mold notably possessing a curved central section mold bottom whose dimensions allow it to be inserted in the hollow at the bottom of the rough shape, and a finishing step of blowing of the rough shape during which the curved central section of the mold is inserted into the hollow central section of the bottom of the rough shape.
BACKGROUND OF THE INVENTION
Processes and setups to obtain containers from rough shapes are now well-known. These allow the user to obtain containers that are able to sustain high temperatures and relatively severe mechanical pressure without losing their shape during use. In such processes, the molding is performed by blowing or by stretch-blowing, from a pre-form made of thermoplastic material whose body is brought to a temperature at least equal to the softening temperature of the material, and this results in an intermediary container of larger size than the finished container yet to be obtained; this intermediary container is then heated to obtain a rough shape of heated, shrunk body, which is then molded to form the final container.
Such processes and installation are, for example, known as European patent EP 442 836 in the name of the applicant.
Despite the fact that this process was vastly superior to previous techniques, it became obvious that the containers obtained by this process had a tendency to lose their shape when filled with hot liquids, and this made the container unstable. Then, the bottom structure itself was reworked, and it was found that the containers that had a curved bottom with an inward convexity, in other words containers with a “champagne bottom” because of the shape of the bottom which resembles that of a champagne bottle, could resist satisfactorily to these conditions.
The various processes and setups were tested and resulted in this type of final container bottom shape. It was determined that the containers that possess the best thermal or mechanical properties during use are those obtained from a rough shape possessing at least a curved primer of inward convexity in the central area, at the bottom on the final container. It was even noted that in certain applications that the rough shape must have a bottom whose shape and measurement must correspond to those of the bottom of the final recipient.
Therefore, the French patent request No 95 01507 presents a process and a setup that obtains a particular champagne-bottomed container from a rough shape whose bottom possesses the shape and size of the bottom of the final container.
Contrarily to the intermediary container and to the final container that are both obtained in a mold, the rough shape is obtained in air, after highly heating the body of the container and thus having provoked a relaxing of the constraints conferred to the thermoplastic material during the transformation of the pre-shape into the intermediary container. The result is that the rough shape resembles a container whose body is vaguely deformed or bloated, but that nevertheless possesses a bottom zone with a shape and dimension predetermined by the process used, that is to say either the final shape of the bottom of the final container, or a primer of the central part of the final container.
But, because of the relative indetermination of the shape of the body of the rough shape, it happens relatively often that the symmetry axis of the bottom zone is offset and/or tilted in relation to the axis of the finishing mold at the moment when the rough shape is placed inside of it. Actually, the positioning of the rough shape in the finishing mold is performed in the known manner with the neck, which is the only part that undergoes no deformation during the different steps of the transformation from a pre-shape to the final container.
The result is that sometimes the bottom area of the rough shape is not correctly centered at the moment of contact with the curved shape of the bottom of the mold, which often causes the bottom of the rough shape to get stuck on the curved shape of the bottom mold in an offset and/or tilted position, causing the final container to be misshapen and unsatisfactory.
SUMMARY OF THE INVENTION
The invention's goal is to remedy this inconvenience, proposing a process and setup allowing the user to obtain a correct centering of the central curved zone of the rough shape in relation to the curved area of the mold bottom.
The goals of the invention are attained by setting up a process such as described in the introduction that is characterized in that, to facilitate the centering of the bottom of the rough shape in relation to the curved central part of the mold bottom, a relative rotation movement between the curved area of the mold bottom and the central part of the rough shape central is performed from the moment that the rough shape is placed into the mold to the moment where the shapes are correctly positioned in relation one to another.
In fact, the relative rotation movement between the bottom of the rough shape and the bottom of the mold increases the sliding of the material on the central section of the bottom of the mold, thus allowing a correct centering.
Preferably, and according to another characteristic, the relative rotation movement is performed by rotating at least the central curved part of the bottom of the mold. Alternatively, even though this is more difficult to achieve, the relative rotation movement is achieved by turning the rough shape within the mold.
The invention also has for a goal a setup for the implementation of the process, characterized in that it can trigger the relative rotation of the rough shape and of the mold bottom.
In a preferred implementation, the means to trigger the relative rotation between the rough shape and the central section of the mold bottom are made up of a pneumatic rotary motor that powers the central part. This solution is particularly advantageous because the container assembly lines already possess the pressurized fluid distribution system as much to blow the containers as to move sections of the assembly line. It is noted that the mold bottom can generally be moved along the axis of the mold, at least to facilitate the setting of the rough shape and to facilitate the de-molding of the container. In other cases, the mold bottoms are moved along the same axis during the finishing phase, as it is the case in the French patent application No 95 01507 that this applicant filed, in order to compensate for the slight shrinking that occurs at the beginning of the finishing blowing and allows contact between the bottom of the mold and the bottom of the rough shape. These movements of the bottom of the mold are achieved with pneumatic devices, and it is therefore relatively easy to selectively divert a part of the fluid that serves in the movement of the mold bottom to power the pneumatic rotary motor.
REFERENCES:
patent: 4315888 (1982-02-01), Hafele
patent: 5520877 (1996-05-01), Collette et al.
patent: 5660902 (1997-08-01), Unterlander et al.
patent: 2450696 (1975-05-01), None
patent: 425360 (1991-05-01), None
patent: 2508004 (1982-12-01), None
patent: 9518005 (1995-07-01), None
McDowell Suzanne E
Sidel
Silbaugh Jan H.
Suhgrue, Mion, Zinn, Macpaek & Seas, PLLC
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