DE8210074U1 - DEVICE FOR PRODUCING A THIN-WALLED, INJECTION-MOLDED PLASTIC CONTAINER WITH A SMOOTH EDGE - Google Patents

Description

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HOECHST AKTIENGESELLSCHAFT HOE 82 / F O? 6 G Dr.DA / cr

Device for the production of a thin-walled, injection-molded plastic container with a smooth edge

The present invention relates to an apparatus for producing a thin-walled, injection molded plastic container with a smooth edge, in which the injection gate is located on the edge.

Cups and cup-like products, e.g. cans, are used as packaging for liquid, pasty or solid filling goods used. In particular for the packaging of dairy products, edible fats, marinades and there is a great need for other foods

Packaging of this type. After being filled with a cover film, they are usually sealed against bacteria, gas and liquids by heat sealing. The container wall can be conical or cylindrical and thereby smooth or strip-shaped, ring-shaped or diamond-shaped
Reinforcements be profiled.

Thin-walled, injection-molded drinking cups with ring-shaped wall stiffeners and reinforced ones

Rand are already known (see US Pat. No. 3,169,688). They are preferred for dispensing hot beverages. An essential feature of this cup is the central position of the sprue pin on the outside of the internally borated bottom. Such cups have sufficient breaking strength and are as
Drinking cup suitable, but not a sufficient smoothness of the cup rim for the bacteria, gas and liquid-tight sealing of a cover film
is essential. The poor quality of the

The edge of the cup is due to the position of the sprue. In order to obtain a burr-free edge, the injection must be carried out at high speed with dense
Positive locking take place.

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In this way, the flow front can move through the adiabatic compression of the air enclosed in the mold heat that there is thermal damage to the plastic material comes in the front area, from which the cup rim is formed.

In addition to the inadequate smoothness of the edge, this thermal damage may also result in insufficient adhesion of the sealed-on cover sheet. A reduction in the injection speed makes the manufacturing process uneconomical and leads to inadequate shaping of the container edge, which is partly due to the then inadequate flowability of the plastic and partly to the effect of the holding pressure which is limited to the bottom and shell area of the container. The result is cracks, sink marks, cavities and other imperfections on the edge of the container. The disadvantages described are all the more pronounced the longer the flow path from the sprue to the most distant corner of the mold, ie here the container edge, the thinner the cup wall and the colder the mold. For this reason, injection-molded, rotationally symmetrical containers have so far been provided with a sprue located in the axis of rotation in order to keep the flow paths as short as possible (see Plastververarbeitung, 1961, pp. 453 ff and 504 ff, Figs. 16, 17, 27, 28) .

Finally, it was also known in the manufacture of a bottle-like hollow body by injection molding To arrange the sprue near the upper opening (on the neck) (see EP-OS 35035). However, this sprue is in addition to the sprue at the bottom of the hollow body, in order to achieve a certain molecular orientation of the polyester used in the area of the bottle neck, problems with the flowability of the

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Plastic does not occur in this hollow body because of the great wall thickness.

There is therefore a considerable need for thin-walled containers with smooth edges. Since it is packaging material is, they should be inexpensive to manufacture.

It has been found that the object can be achieved if the containers are manufactured by injection molding and does not attach the sprue to the bottom of the container, but to the edge, preferably at the edge.

The subject of the invention is thus the device described in the claim.

All plastic containers are to be understood as containers that are open at the top and have conical to almost cylindrical walls, with height and largest Diameter can be in any ratio to each other. The height is preferably one-half to three times the largest diameter. The height is about 5 to 15 cm, the largest diameter about up to 10 cm. The container to be produced in the device according to the invention can have any cross-section have, preferably the cross section is circular.

The wall thickness of this container is as small as possible for economic reasons, it is in the range of 0.25 to 0.75 mm. The edge is 2 to 10 mm wide and 0.25 to 2 mm thick.

The container is manufactured by injection molding. The sprue is attached to the edge of the container. The sprue can be on the outside or on

-lt is located on the inside of the edge, preferably it is on the outside. This arrangement has the effect that when the melt is injected, the edge is first formed and the melt flows from this tool section according to the principle of the overflowing weir into the cavity areas for the side wall and bottom of the container. There is also the fact that the container edge solidifies during the subsequent cooling under the action of the holding pressure and is thus perfectly shaped even when thickened, namely with a planar or rounded design. Thermal damage and its described consequences do not occur. The cavity ventilation necessary for the proper shaping of the side wall and floor area can be ensured on the one hand by the split injection molding tool and on the other hand by a ventilation gap in the tool core. It could not be foreseen that with this gate position and the extremely narrow flow channels a perfect injection-molded part would have to be formed.

The plastic container is injection molded according to the methods known for the various thermoplastics Procedure. The process data, such as melt temperature, mold temperature, injection pressure and time, reprint can be found in the relevant brochures and leaflets. You are from the Dimensions of the container to be sprayed depend on.

In the device to be used for the manufacture of the container, the runner is arranged in such a way that later the sprue is on the edge of the container. Although the well-known, the runner on The bottom of the container having devices can be retrofitted by relocating the sprue to the edge of the container, is preferably a special one Device used.

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This device consists of two symmetrical mold halves, which have depressions, each correspond to one half of the outer shape of the container to be manufactured. Enclose the two halves of the mold a core which corresponds to the internal shape of the container. Mold halves and core thus form between the mold cavity for the container to be manufactured. The longitudinal axis of the core is in the mold parting plane (Tool parting plane). In one mold half, the runner is arranged in such a way that it is attached to the part the cavity ends in which the edge of the container is formed.

The core is provided with devices that make it easier to remove the container from the mold. For this purpose is the The part of the core lying against the bottom of the container is preferably designed as a valve disk, which in Is movable in the direction of the longitudinal axis and the compressed air releases the path that brushes the container from the core. If containers with a concave bottom or a bottom with a standing rim are to be produced, it is recommended that the To make the whole core movable in the longitudinal direction, which is done by inclined columns, rectangular guides, dovetail guides or can be done hydraulically. 25th

The figures show devices according to the invention. Show it

Figure 1 shows a preferred device for producing the container in the closed state, Figure 2 shows the same device in the open state and

FIG. 3 shows another possibility of a device for producing a container.

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In Figure 1, a preferred device for producing the container is shown in the closed state. Enclose the two mold halves (1) and (2) the core holder (3) and the core (4) such that between the mold halves (1) and (2) and the core (4) the mold cavity for the container is created, which emerges from the bottom (5), the side wall (6), the edge (7) and the sprue (8). The tool division plane is indicated by (9). The part facing the bottom (5) of the container of the core (4) is designed as a valve plate (10) which can be moved by the push rod (11) so that An annular gap (12) can form between the valve disk and the rest of the core. Through the line (13) compressed air flows into the interior of the core. In the shape half (1) the runner (14) is arranged in such a way that that it ends at the sprue (8) on the edge (7) of the container,

The device is with the usual and known devices for cooling, for example by the

Channels (15), temperature control of the sprue channel (14), for

Clamping the device on the clamping plates of the injection molding machine, for connection to the spray nozzle and moving the mold halves (1) and (2), the core holder (3) and the push rod (11) provided in the figure 1 are not shown.

To produce the container, the plastic melt is not removed from one of the devices when the device is closed Injection unit shown through the sprue channel (14) into the Mold cavity injected, initially forms the edge (7) and then flows according to the principle of the overflowing weir into the areas of the side wall (6) and the bottom (5). After a sufficient cooling time, the device is opened, the mold halves (1) and (2) being moved apart and also the core holder (3) via a suitable device by half the amount of the opening path of the

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Mold halves is moved in the same direction, so that the Container can be removed from the device. As a rule, only the mold half that does not have a sprue channel is used owns, in the present case, the mold half (2) when opening the device while moving the other Mold half (1) remains. The core carrier (3) moves in the same direction and prints at the same time the push rod (11) the valve disc (10) down a little so that a narrow gap (12) between

Valve plate (10) and the rest of the core (4) are formed,

compressed air flows through the upper line (13) and strips the container from the core.

FIG. 2 shows the device in the open state after the container has been stripped from the core. The gap (12) between the valve plate (10) and the rest of the core ⁽¹ O is not yet closed. At the container, the label (16) to detect the tool separation plane (9).

Figure 3 shows a possibility of a conventional device for producing containers for the retrofit. Such a device consists of a female mold (1a) and a male mold (2a) with a core (4). The sprue channel (14) is brought up to the sprue (7) through the die (1a). A plug (17) closes the lateral hole (14a).

Claims (1)

- 8 - hoe 82 / F 076 G claim Device for the production of thin-walled plastic containers with a smooth edge by injection molding, thereby characterized in that it consists of two symmetrical mold halves which have recesses which each correspond to one half of the outer shape of the container to be manufactured, and enclose a core which corresponds to the inner shape of the container corresponds, with the longitudinal axis of the core in the mold parting plane and in one of the two Mold halves a runner is arranged such that it ends at the part of the mold cavity in which the Edge of the container forms.