Injection mold for molding of a glazing

Details Injection mold for molding of a glazing Injection mold for molding of a glazing

2000-06-21

2001-10-16

Nguyen, Nam (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With means to cause relative movement between mold and charger

C425S183000, C425S442000

Reexamination Certificate

active

06302681

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the encapsulation or duplicate molding of a glazing of glass and/or plastic by injection of a plastic on at least one part of the glazing. The invention relates in particular to a process and a duplicate molding device using this process.
2. Description of the Related Art
The process of encapsulation by injection of plastics on at least one part of a glazing placed in a mold includes the following operations: placing the glazing in a mold, optionally, placing elements in addition to the glazing in the mold, before and/or after the placing of the glazing, closing and pressurizing the mold, injecting plastics, releasing the molding pressure, polymerizing or cooling of injected plastic, opening the mold, extracting the duplicate molded glazing.
These various operations can be performed at a single station. In this case, the press, placed at this station, is monopolized during all these operations. Furthermore, the press must then be provided with a large opening width to facilitate access to the contents of the mold. These two imperatives necessitate a low rate of production and therefore a high cost.
To improve this rate, a process of the turntable type has been proposed; the various operations constituting this process are performed at different stations, with transfer by rotation from one station to the next. A turntable process has been proposed in which all the operations are performed at four different stations. The production of a duplicate-molded glazing thus requires the use of four pieces of equipment (molds). The investment in equipment for this type of device is therefore high.
Furthermore, in case of a problem on one of the pieces of equipment, the entire system is tied up. For obvious reasons of equipment cost, this device has been applied only to the production of parts with small dimensions, produced on a large scale.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the above drawbacks.
The invention has another object to minimize the time of a production cycle of a duplicate-molded glazing, with flexibility of use and a reduced cost.
The invention proposes a process of injecting plastics on at least a part of a monolithic or laminated glazing, of glass and/or transparent plastic, placed in a mold situated horizontally, a process in which the essential operations are performed at two different stations, the operations of molding pressurization of a mold, of injection of plastics, of release of the molding pressure in the mold being performed at one station, known as the main station, while the essential additional operations are performed on a second mold at another station, known as an auxiliary station, the two molds each being assigned to an auxiliary station and being transferred from their auxiliary station to the main station and vice versa separately. The essential additional operations are, in particular, the placing of the glazing in the mold, the optional placing of additional elements or inserts, the closing of the mold, the opening of the mold, the removal of the duplicate-molded glazing.
One of the advantages of the process operating with two molds, each of them being assigned to an auxiliary station according to the invention, is that it makes it possible, using two pieces of equipment (molds), to duplicate mold jointly two glazings which can, if necessary, be different as to their shape and/or dimensions. By mold is meant, according to the invention, the lower old and the countermold.
While a portion of the operations of the process occur at the main station for a glazing contained in one mold, other operations of the process are performed at the auxiliary station for a second glazing contained in another mold. The rate of production is thus increased without thereby multiplying the number of pieces of equipment.
According to an embodiment of the invention, a main station and two auxiliary stations with two pieces of equipment are used.
In this case, a transfer is envisaged for the direct passage from each of the two auxiliary stations to the main station and vice versa. Since the transfers are separate, in case of any trouble at an auxiliary station, the other auxiliary station can function in connection with the main station.
In another variant of the invention, a main station and more than two equivalent auxiliary stations are used with a direct transfer for a mold from each of the auxiliary stations to the main station and vice versa.
According to an advantageous characteristic of the process according to the invention, after the closing of the mold, an intermediate pressure is applied to the glazing in the mold, this intermediate pressure being, preferably, maintained during the transfers of the mold.
By intermediate pressure is meant a pressure higher than the atmospheric pressure, but lower than the molding pressure.
This intermediate pressure applied to the glazing at the auxiliary station after the closing of the mold makes it possible to regulate the ability of the glazing to bear molding pressures.
A reduced pressurization of the mold before the injection operation is particularly advantageous. It thus makes it possible to limit the danger of breakage and, if necessary, to withdraw the broken glazing before reaching the end of the production cycle of the duplicate-molded glazing as a result of any detection system. Such breakage can result from a poor placing of the glazing in the mold or from a defect in the quality of the glazing.
Another advantage of a reduced pressure during the transfer of the mold after the injection operation is that this transfer time is used for the polymerization and/or the cooling of the plastic.
The invention also relates to an encapsulation device comprising a main station equipped with a press and an injection unit and at least two auxiliary stations, connected directly to the main station with transfer tables that are separate from one another, and at least two pieces of equipment or molds.
One of the advantages of the invention is that at each auxiliary station at least one mold provided with a transfer device is assigned. This device is, in particular, a transfer table having a bidirectional linear movement.
Thus, according to the invention, each mold is autonomous; a piece of equipment can be disabled without the entire device being immobilized. The idle times relative to the restarting of the process for injecting the plastic after a stop corresponding to a purging of the injection head are thus avoided. Actually, the constituents of the plastic, during this period, can easily be degraded, indeed become solidified in the injection unit. Furthermore, the mold of a produced part corresponds to the produced part; the production of a part therefore uses only one piece of equipment.
These molds can receive glazings of distinct shapes and/or dimensions. For example, a rear window and an automobile windshield can be produced jointly.
According to a preferred embodiment of the invention, the closing and injection station comprises only one press and only one injection unit. Of course, to be able to inject plastics of different nature, or at different flow rates (the duplicate molding of a windshield does not require the same flow rate as the duplicate molding of an automobile rear window), the press and the injection unit are suited, according to the invention, for these additional constraints. Thus, the press can be equipped with an “all or nothing” hydraulic closing system with pressure regulation and the injection unit is advantageously controlled by a device provided with a software package comprising several specific injection programs. This device provided with a software package further makes it possible to regulate the entire process, several orders being able to be given simultaneously. These elements will be described in a more detailed way in the following description.
To improve accessibility to the contents of the mold, according to a preferred embodiment of the invention, the mold and the

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