Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Reexamination Certificate
2002-12-03
2004-11-09
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
C264S534000, C264S535000, C425S525000, C425S526000
Reexamination Certificate
active
06814922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for the production of a container with an opening, whose opening axis is at an angle to the container axis. In the method, a blank is introduced into a blow mold, and the container component of the blank is molded in the blow mold by means of blowing. A blow mold has in a blow mold body a blow mold cavity corresponding to the outer shape of the container, and a stop zone for a fixing region on a blank that can be inserted into the blow mold. In addition to such a blow mold, a blowing device also requires a blowing nozzle that can be sealed on the blank. Additionally, such blowing devices usually have a stretching pin for the stretching of the blank.
2. Discussion of Related Art
Bottles and containers blown with plastic blanks usually have an opening, the axis of which coincides with the container axis, or is arranged parallel to it. The blank is inserted into the opening being arranged orthogonal to the blow mold body into the blow mold cavity using tongs, and contacts the blow mold with a fixing region in the neck area. The insertion direction of the blank is parallel to the blowing mold axis. The walls of a container part of the blank are thereby positioned at a distance to the limitation of the blow mold cavity being approximate equal around the perimeter. The fixing region is now pressed using the blowing nozzles, and the blank is blown until the plastic walls have the shape of the blow mold cavity. Further in most cases a stretching pin is inserted into the blank, and the blank is stretched with it in the direction of its container axis. Practically at the same time, the blank is blown, and by that the material of the blank walls is stretched.
If it should be departed from the rule of the coincidence of the opening axis and the container axis, irregularities in the wall thickness are to be expected due to varying stretching conditions in the different areas of the blank walls. In the case of parallel axis, an irregular stretching of the blank walls can be counter-acted upon in narrow limitations, for instance by means of aimed warming of the blank. However, if the opening axis even extends at an angle to the container axis of the blow mold, the distances between the walls of the inserted blank and the limitations of the blow mold cavity vary with increasing distance from the opening. Achieving a nearly equal wall thickness of the finished container seems to be impossible with common rotation symmetric blanks with evenly thick walls and a common blowing method, or a common stretching and blowing method.
A method and a device for mold blowing of a plastic container with an opening axis extending at an angle to the container axis is known from EP-A-0361 141. The container is blown from a blank in a blow mold. For this purpose, the blank is inserted into a blow mold. Its fixing region in the area of the container opening is pressed onto the blow mold by means of a mold piece for the molding of the container's mouth piece. The mouthpiece is sealed with a blowing piece. A stretching pin extends through the blowing piece into the blank. A streching pin extends through the blowing piece into the blank. The blank can be stretched with the stretching pin. It also has a multitude of air intakes, through which compressed air is pressed into the blank during the blowing of the blank into a container.
The opening axis of the blank and the blow mold are directed vertical, namely parallel to a insertion direction of the blank and to a blow mold axis. In order for the neck axis of the container finally being at an angle to the container axis, a cavity axis of the blow mold cavity corresponding to the container axis is inclined at an angle to the insertion direction and the blow mold body axis, respectively.
In order to avoid a part on the neck area of the container resulting too thin, the container part of the blank is bent in the direction of the cavity axis. This can occur by means of molding the blank in a special mold before inserting it into the blow mold. It can also be deformed inside of the blow mold after insertion by means of a slide, or by means of stretching on a circular path with a curved stretching pin.
All of the suggested variations of the method for the molding of the blank need, besides insertion and blowing, an additional process step. This step increases the production time for a container.
It is therefore known that in a method for the production of a container with an opening, the opening axis of which is at an angle to the container axis, a blank is inserted into a blow mold, a fixing region of the blank is pressed against a stop zone on the blow mold, and the blank is pneumatically molded in the blow mold.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to suggest a method and a device, with which it is possible, especially by using common rotation symmetric blanks, to blow a container, the final opening axis of which is arranged at an angle to the container axis. The wall thickness of the finished container shall be nearly constant at a cross section crosswise to the body axis. Particularly, the production time for a container shall be as short as possible.
This object is solved by pressing the fixing region of the blank against a stop zone on the blow mold being inclined at an angle other than 90° with respect to the insertion direction of the blank. Thus it is molded right during the insertion and stretching in such a way that an opening axis of the blank is at an angle to the container axis of the blank. By that an additional and production time extending molding step can be eliminated.
The angle between the axes of the blank is coordinated with the angle between the opening axis of the container and the container axis. Due to this, the walls of the container piece of the blank inserted into the blow mold and the blow mold cavity are, independent of the distance to the opening, at an approximate even distance to each other. This allows the use of blanks that are rotation symmetric at least in the container piece.
A container is produced using such a method, which has in particular container walls arranged around a body axis, and a container bottom, and the container bottom of which is usually parallel to a plane extending at an essentially right angle with respect to the container axis. The axis of its opening positioned opposite of the container bottom is at an angle to the body axis. Therefore, such containers, especially tilted neck bottles intended for toilet bowl cleaning, are advantageously produced by blowing in a blowing mold a blank made of thermoplastic plastic material and having walls, a bottom, and a pre-molded opening. A rotation symmetric blank is thereby molded before the blowing of the container piece in such a way that an axis extending through the opening of the molded blank extends at an angle to the symmetry axis of the blank's walls (container axis). The container axis of a rotation symmetric blank is coincident with the original rotation or symmetry axis of the blank. Preferably, the angle of the opening axis to the symmetry axis of the walls is smaller, or equally large, however especially preferably equally large as the deviation to be achieved of the opening axis to the body axis.
This measure ensures that a rotation symmetric blank can be used, and the walls can have wall thickness deviations coming from the tilting only in the already thicker neck area of the finished container. The finished container has practically no relevant wall thickness deviations in the walls and in the bottom, as with the previously mentioned tilting the walls of the blank are oriented approximately parallel to the wall of the container to be achieved. A difference between the angle of the container part axis to the opening axis of the blank, and the cavity axis to the opening axis of the blow mold cavity, can preferably be up to 6, or in case of low quality requirements, even up to 9 degrees, before the resulting wall thickne
Alpla-Werke Alwin Lehner GmbH & Co. KG
Carlson Dale L.
Kinney Michael K.
McDowell Suzanne E.
Wiggin and Dana LLP
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