Refrigeration – Processes – Treating an article
Reexamination Certificate
1999-08-17
2001-05-01
McDermott, Corrine (Department: 3744)
Refrigeration
Processes
Treating an article
C425S526000, C425S548000
Reexamination Certificate
active
06223541
ABSTRACT:
The object of the present invention is a method and a device for the after-cooling of a preform which was produced in the injection molding process
BACKGROUND OF THE INVENTION
Such preforms are produced in the injection molding process with the aim of blowing from them—in a later process step of a subsequent hollow blast process—hollow body such as, for example, a plastic bottle, a plastic container or the like. In order, therefore, to produce such a preform in the injection molding process there is required in a manner known per se an injection molding machine which essentially consists of two mold halves movable with respect to one another, in which the one mold half which is connected to an extruder injects corresponding hot-fluid plastic material into the mold half, after which then the mold half is cooled and the preform is now present in the injection molding machine in the allocated mold core.
In order properly to cool such a still very hot preform, it is a known practice to remove the preform from the injection molding machine and to bring it into a so-called after-cooling plate. In the after-cooling in the after-cooling plate, it is a known practice to receive the preform in corresponding cooled cavities of the after-cooling plate and to cool this preform at least on its outer circumference. As cooling agent there is used here in particular a liquid cooling medium such as, for example, water, oil or the like. It is also possible, however to use cooled air.
With this after-cooling of the preform in the after-cooling plate there is present, however, the disadvantage that the preform is only insufficiently cooled, because precisely the cooling performance in this after-cooling process is limited. As stated, the cooling occurs only on the outer circumference of the preform, which leads to the result that a temperature gradient arises in the direction of the interior space of the preform, which leads to a deterioration of the plastic material. Namely, in such an after-cooling, the plastic material tends toward a transformation of the crystal structure into the crystalline structure form, which severely impairs the quality of the preform. In the subsequent hollow blast process the preform, therefore can be further processed only with difficulty and with losses of quality.
OBJECTS AND SUMMARY OF THE INVENTION
Underlying the invention is the problem of further developing a process and apparatus for improving the cooling performance in an after-cooling plate so that there is achieved a substantially better quality of the preform material, with better cooling performance, and so that the cooling agent is recovered.
For the solution of the problem posed the process/method is characterized in that during the after-cooling also the interior space of the preform is cooled by means of a cooling medium.
With this essential process step there is present the advantage that now the cooling of the preform no longer occurs solely from its outer circumference inward, but that the preform is now also cooled in its interior. The precondition here is that the preform is open at least on one side and is accessible from outside from the after-cooling plate, so that from this opening the cooling medium can be introduced into the interior space of the preform.
Here there are claimed by the invention all known types of cooling medium. In a preferred form of execution the process is executed by the means that as cooling medium cooled, dried air is injected.
As temperature for this cooling air there can be used here room temperature or a cooling temperature going as low as −35° C., at which moisture contents ranging from 0% relative humidity to maximally 98% relative humidity can be used.
If in particular cooled, dried pressing air is used, then temperatures in the range from +5° C. to maximally (sic) −35° C. are preferred, there being used with these air temperatures an air near the dew point, just short of the dew point.
Obviously the use of air as a cooling medium is not is not to be understood as restrictive for the present invention. There can also be used other cooling media, such as, for example, an air that is enriched with water in spray form, or only a liquid cooling medium such as, for example, cooled water at room temperature, or other liquid cooling media, such as, for example, alcohol or alcoholic solutions.
The process relates generally to the feature that the interior space of the preform is cooled with the preferably gaseous medium cooling medium. For this it is required that the cooling medium be blown or injected into the interior space of the premold. For this form of execution there are a number of different possibilities which are all claimed as essential to the invention.
In a first form of execution of the present invention it is provided that the preferably gaseous cooling medium is brought in through a feed element in the form of a mouthpiece onto the preform and the gaseous cooling medium is pressed into the preform under excess pressure.
In the interest of simplicity in the following description of the invention there is taken as starting point a gaseous cooling medium, although the present invention also lays claim to all other types of cooling media.
When, therefore, such a gaseous cooling medium is injected into the preform, then in a first form of execution it is provided accordingly that a corresponding blast mouthpiece is placed on the opening of the preform and the preform is blown out with this cooling medium.
In a second form of execution of a corresponding device it is preferred if the blast mouth piece extends not only to the opening of the premold, but if the blast mouthpiece plunges into the premold, so that this blast mouthpiece is constructed as a plunger tube which plunges as deeply as possible into the preform and provides this with cooling air on its inside from its base surface, which cooling air flows along the inner surface of the preform in upward direction and again leaves the preform.
Therewith there is achieved a substantially better and more intensive flow-treatment of the preform because, on the one hand, the cool plunger tube plunges into the preform and already cools the preform solely by a corresponding cold radiation and, on the other hand, the cooling medium itself also cools the preform in upward direction, increasingly from its inner base surface.
To the earlier mentioned cooling media it is further added, that besides the previously mentioned gaseous cooling medium there can also be used corresponding liquified and deep-cooled gases, such as, for example, liquid air, liquid nitrogen or other liquified deep-cooled air mixtures.
In a preferred form of execution of the plunger tube it is provided that the plunger tube has merely a lower, face-side opening, which is directed essentially upon the inner base region of the preform to be cooled, so that therewith a corresponding flow reversal takes place in the zone of this mouthpiece and the air then rises in the interspace between the outer circumference of the plunger tube and the interior space of the preform.
In another form of execution it is provided that the plunger tube also has corresponding transverse bores, so that, therefore, not only a downward directed, face-side open outflow tube is present, but there still occurs also over corresponding transverse bores the air outlet in the zone lying opposite the inner wall of the preform.
The plunger tube can be made of a plastic material or of a metal material and its inside diameter does not absolutely have to be adapted to the inside diameter of the preform; i.e., the inside diameter of the plunger tube can also be substantially less than the diameter of the corresponding preform.
The outflow opening in the zone of the plunger tube can also be provided with corresponding nozzles in order to generate either corresponding turbulence in this zone or an aimed flow-treatment of certain zones of the preform which for certain reasons must be especially and strongly cooled.
Aimed nozzles, therefore, can be used in connection with
Baker & Daniels
Drake Malik N.
Fasti, Farrag & Stipsits GesmbH
McDermott Corrine
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