DE1936648A1 - Method and device for reducing the volume of a plastic container - Google Patents

Description

DlPL-ING. H. FINK PATENTANWALT · 7300 ESSLINGEN (NECKaR) ■ HINDENBURGSTRASSE

Patent attorney FINK - D 7300 E «lingen (Neckar), HindenburgitraS» 44 ·

July 17, 1969 Be P 5745

Gerhard Hansen, 7013 Oeffingen, Krs. Waibling'en, Hofener Strasse 4-7

"Method and device for reducing the volume of a container made of plastic"

The invention relates to a method for temporarily reducing the volume of an in a closed hollow mold located container made of plastic, in particular shortly before its closing, and a device for carrying out the Procedure.

Various plastics shrink during the cooling process. When the container is cooling down, its contents are smaller and there is a risk that it will an undesirable pressure forms in the container, which leads to bulges and the like. Especially with in cross section round containers, the bottom is pressed outwards, which impairs their stackability. With oval or slightly domed or containers with flat surfaces, the surfaces that are most likely to give way are deformed, thereby reducing the appearance the container can be affected.

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009888/1876

■ 7/17/69 Be 'P 574-5

The invention therefore aims to provide one by shrinking to reduce or prevent overpressure occurring in the closed container. This goal is achieved according to the invention achieved in that at least a part of the container belly is at least until the container is closed sustained pressure corresponding to the shrinkage of the container is applied. The pressure increases the volume of the open container until it is closed. The closed and pressure-free container then has first a larger volume, so that an overpressure in the container due to its shrinkage can only arise when the Container shrinks more than the previous increase in volume. The shrink volume and the enlargement volume can be mutually adjusted so that a container can be kept practically free from internal pressure, even if he is heavily filled.

The pressure to be exerted on the container before it is closed can be generated in different ways. That's the way it is for example with a container that is at least under With the help of an external negative pressure, it is possible to inflate the inflated belly of the container under positive pressure to put. But it is also possible to apply the desired pressure mechanically. .

A device for performing the method is thereby. characterized in that at least one wall part of the hollow mold located in the region of the belly of the container is by means of of a drive motor in the direction of the container and for a time to be chosen at will in the on the shrinkage of the container dependent displacement position is to be held on a stop member. With the help of the wall part mechanical pressure is applied to the container. Such a measure has the advantage that the displacement

7/17/69 Be P "574-5

of the wall part "can be limited and precisely adjusted, so that the desired effect within the through the shrinking process "Conditional limits and is achieved within close tolerances. The wall part is the outer shape of the container adapted so that the shape of the container is not "adversely affected" by this.

Further advantageous features emerge from the following description in connection with the claims and the drawing. In this is a device for temporarily reducing the volume of a container as an embodiment of the subject matter of the invention shown schematically. Show it

Pig. 1 shows a longitudinal section through a production mold along line I-I in Pig. 2,

Pig. 2 shows a section along line II-II in Pig. 1, Pig. Figure 3 is a side view of part of the manufacturing mold, Pig. 4 shows a cross section along line IV-IV in Pig. 3 ·

On a table 1 is a carriage 2 with the help of a working cylinder 3 from a position below a position not shown To move the extruder to a position below a feed and flushing organ, not shown.

The carriage 2 carries two sub-mold halves 12 and 12 which can be displaced transversely to the direction of displacement of the working cylinder 3 12a. A suction head 14, 14a is provided on each of the lower mold halves, between the and the associated lower mold half, an upper mold half 16 or 16a is to be displaced in the same direction as the lower mold halves 12, 12a. The lower mold halves 12, 12a, the suction heads 14, 14a and the upper mold halves 16, 16a are connected to sources of negative pressure that can be controlled at will connected. The lower mold half 12, 12a and the. Suction head 14, 14a can be connected directly to one another.

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7/17/69 Be P 574-5

The lower mold half 12 is secured by means of a working cylinder 17 and to move the upper mold half 16 individually by means of a working cylinder 18.

The parts of the production mold shown on the right in FIG. 1 have the same reference numerals as those shown on the left Provided parts, wherein the reference numerals of the right parts also have the letter a.

An intended for forming the container abdomen wall portion 26 of the lower mold half 12 is slidably supported in dieserin direction of arrow A in Fig. M- and for this purpose has the other mold parts of the lower die half corresponding guide surfaces. For the purpose of displacement within the closed production mold 12, 12a, the wall part 26 can only form a limited area of the mold wall intended for the shaping of the container.

The wall part 26 has outwardly projecting arms 27 and 28 on each of which a working cylinder 29, 30 attached to the lower mold half 12 engages. On that of the working cylinders The side facing away from the 29 »30 side is eiü on the manufacturing mold Holding arm 31 and 32 attached, each having a screw 33 as adjustable stop member for the arm 27 and 28, respectively. The screws 33 of two interacting lower mold halves 12 and 12a are optionally arranged at different heights so as not to impair the closing of the production mold.

The production form is otherwise corresponding to that in German Auslegeschrift 1 272 807 shown production form educated. The device according to the invention can also be applied to other forms of manufacture, e.g. to in the German Auslegerschrift 1 297 525 shown manufacturing forms. . c

7/17/69 Be P 574-5

In the selected embodiment, "is at the beginning of the working cycle, the open production mold below the mouth of the extruder, which squeezes out a piece of tubing. As soon as this has reached a sufficient length, the two lower mold halves 12, 12a move together. To inflate the Hose piece into a container, a negative pressure is made effective thereon via the lower mold halves 12, 12a. the upper mold halves 16, 16a are of the lower mold halves 12, 12a taken, but not closed. The hose section is pulled together at its upper end by the ■ Suction heads 14, 14-a held before it is from the Extruder is separated.

The production mold then moves under the filling element, the mouth of which opens with the interposition of the plastic tube. the Lower mold halves 12, 12a are seated. If necessary, the filling element is used to completely inflate the container belly Compressed air is blown in, which may only escape from the container under a certain pressure can. Thereafter, the filling material is introduced into the container belly while displacing the air, if necessary compressed air. After the container has been filled, the filling element is raised. Before closing the upper mold halves 16, 16a for formation of the container head, the working cylinders 29, 30 are actuated and the wall part 26, 26a is displaced, whereby the volume of the container belly is reduced. The displacement only one of the wall parts is sufficient. Only then are the upper mold halves 16, 16a closed to form the container head and its outside is subjected to a negative pressure. The filled and closed container is opened by opening the Ejected manufacturing form. A container that has remained in a manufacturing mold can be moved back and forth of the wall part 26 can be removed from the molded part. Thieves-

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Removable parts of the manufacturing mold go after ejection

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17.7-69 Be P 574-5

of the finished container back to their original position. Once the manufacturing mold has arrived under the extruder, a new cycle can be carried out.

The wall part 26 is displaced by such an amount as the reduction in volume when the closed container cools and, if necessary, the change in volume of the product assuming the ambient temperature. This causes a pressure to develop in the container and its result caused deformation counteracted.

In the case of the lower mold half 12, 12a, which has a vacuum chamber .with leading to the wall forming the container to be formed Has bores, the container can instead of or in addition to the mechanical deformation shortly before closing of the upper mold halves 16, 16a are exposed to a slight overpressure of e.g. 100 mm WS, which reduces the shrinkage of the container material and the change in volume of the product is selected accordingly.

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Claims (6)

7/17/69 Be P 574-5 Expectations Device for temporarily reducing the volume of a container located in a closed hollow form Plastic, especially shortly before it is closed, characterized in that at least one in the area wall part (26) of the hollow mold (12, 12a) located on the belly of the container by means of a drive motor (29, 30) towards the container and for an arbitrary time in that of the shrinkage of the container dependent displacement position is to be held on a stop member (33). 2. Apparatus according to claim 1, characterized in that the displaceable wall part ° (26) in a solid wall part of the hollow mold (12, 12a) is fitted and guided in this. . .. - 3 »Device according to claim 1 or 2, characterized in that the displaceable wall part (26) after outside protruding arms (27, 28), each of which has a Drive motor (29 »30) causing longitudinal displacement engages, and that the stop member designed as a screw (33) is screwed into a holding arm arranged parallel to it and attached to the hollow mold (12, 12a). 4. Method of temporarily reducing the volume of a in a closed hollow shape, a plastic container, in particular shortly before it is closed, characterized in that at least s on part of the container belly, the shrinkage of the container continues at least until the container is closed The appropriate pressure is applied to the container. 009886/1876 • ■ 7/17/69 Be P 574-5 5. The method of claim 4, "wherein the container at least with the participation of an external negative pressure is bloated, characterized by that the inflated belly of the container is pressurized. · ■ · * 6. The method according to claim 4 ·, characterized in that the pressure is exerted mechanically.