WO2021144392A1

WO2021144392A1 - A method for manufacturing a container

Info

Publication number: WO2021144392A1
Application number: PCT/EP2021/050744
Authority: WO
Inventors: Benny E. NIELSEN
Original assignee: Berry Superfos Randers A/S
Priority date: 2020-01-14
Filing date: 2021-01-14
Publication date: 2021-07-22

Abstract

The present disclosure envisages a method for manufacturing a container. The container manufactured using the method is without visible separation lines or moulding marks. The method does not require high injection moulding pressures. The method is suitable for moulding thin walled containers. The method comprises the step of providing an injection mould (150) having an internal cavity (160) which has a bottom part (170) and a sidewall part (180). The bottom part (170) is filled with a fluid plastic material using at least one first fluid injection nozzle (200). The fluid plastic material is then filled in the sidewall part (180) using second fluid injection nozzles (210), when the bottom part (170) has been completely filled and while the fluid plastic material in the bottom part (170) remains in a molten state. The second fluid injection nozzles (210) are placed at the interface between the bottom part (170) and the sidewall part (180).

Description

A METHOD FOR MANUFACTURING A CONTAINER

FIELD

The present disclosure relates to the field of methods for manufacturing a container, and more particularly, to plastic injection moulding methods for manufacturing a container. BACKGROUND

Manufacturing of containers using a plastic injection moulding method is well known in the art. Typically, a single nozzle is used to introduce a molten plastic material into the cavity of an injection mould. The nozzle is typically positioned at the center of the bottom portion of the cavity, either on the inner side of the container or the outer side of the container. Containers manufactured using a single nozzle can be made in many different sizes. If a container has thin walls, high injection pressure is required to be maintained to make sure the viscous plastic can flow through the narrower portion of the cavity to form the thin walls. To maintain high injection pressure, high closing force is required to be applied on the mould to keep the mould in a closed position during the operation. Further, if the container has a rim portion, the plastic needs to flow through the bottom portion, then up the sidewalls and further to the rim portion. This again requires high injection pressures.

Another known method, see WO 2016/190736, involves pouring of plastic material into the cavity in two stages. In a first stage, the material is filled, via a central nozzle, into a part of the cavity which resembles the shape of the bottom portion of the container. When the material in the bottom portion is completely cooled, the second stage is initiated, wherein the plastic material is filled in another part of the cavity resembling the sidewall portion of the container via additional side nozzles. More specifically, in this method, the central injection nozzle is operated to inject the plastic material into the bottom portion. When the bottom portion is almost full, the central injection nozzle is stopped and the process will wait until the bottom portion is cooled. Then the peripheral injection nozzles are operated to inject material. Some of the material will engage with the bottom portion and some of the material will spread out up the side walls of the container. The purpose of this known method is to reduce the forces needed to maintain the mould in a closed position during the moulding procedure. This method is however associated with drawbacks as well.

Another prior art method is used to manufacture large items where a lot of plastic material needs to be injected. In these situations, the injection process is sometimes arranged such that multiple injectors are used and the plastic is injected into the different injectors sequentially. This is typical for large items such as car bumpers, etc... An example when manufacturing large flower pots is provided in NL 1033143 Cl. This approach spreads the injectors out based on flow paths and flow volumes.

Therefore, there is felt a need to provide an alternative method to manufacture a container that alleviates the some of the drawbacks of the prior art.

OBJECTS OF THE INVENTION

An object of the present disclosure is to provide a method for manufacturing a container that does not generate visible separation lines on a manufactured container.

Another object of the present disclosure is to provide a method that facilitates manufacturing of containers with thin walls without requirement of high injection moulding pressures.

Yet another object of the present disclosure is to provide a method for manufacturing a container which can be executed using lower cost moulds and lower cost moulding machines. SUMMARY

The present disclosure envisages a method for manufacturing a container. The method comprises the following steps. Initially, an injection mould is provided. The injection mould has an internal cavity which has a bottom part and a sidewall part extending from the bottom part. The internal cavity replicates a shape of the container to be manufactured. The container to be manufactured also has a bottom part and a sidewall part extending from the bottom part. The bottom part of the internal cavity is filled with a fluid plastic material using at least one first fluid injection nozzle. Further, the fluid plastic material is filled in the sidewall part of the internal cavity using a set of second fluid injection nozzles when the bottom part of the internal cavity has been completely filled with the fluid plastic material and while the fluid plastic material filled in the bottom part remains in a molten state. The set of second injection nozzles is placed at the interface between the bottom part and the sidewall part of the internal cavity of the mould.

It should be emphasized that the term "comprises/comprising/comprised of" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. BRIEF DESCRIPTION OF ACCOMPANYING DRAWING

Figure 1 illustrates a perspective view of a container manufactured by the method of the present disclosure.

Figure 2, Figure 3, and Figure 4 show sectional views of a mould and fluid injection nozzles depicting various stages of the method of the present disclosure. In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.

DETAILED DESCRIPTION The present disclosure discloses a method for manufacturing a container. The steps of the method are elaborated in the subsequent paragraphs.

Initially, an injection mould is configured to manufacture a container 100. Figure 1 illustrates the container 100 having a bottom portion 110 and a sidewall portion 120 that can be manufactured using the method of the present disclosure. It is to be noted that the configuration and shape of the container 100 shown are only for the purpose of explanation. Any container having shape and configuration different than the container 100 can be manufactured using the method of the present disclosure. Schematic sectional views of a typical injection mould 150 are shown in Figure 2, Figure 3, and Figure 4. The injection mould 150 has an internal cavity 160 formed therewithin. The mould is shown very schematically for the sake of simplicity. The person skilled in the art of moulds will be able to provide a suitable mould. The cavity 160 is so configured that when molten plastic material is filled in the cavity 160, the plastic will take the shape of the container 100. Once the mould is filled, the plastic will cool and the mould will be opened to remove the container.

The internal cavity 160 has two parts, a bottom part 170 and a sidewall part 180 extending from the bottom part 170. The internal cavity 160, i.e., the bottom part 170 and the sidewall part 180, replicates the shape of bottom portion 110 and the sidewall portion 120 of the container 100 respectively. The sidewall part 180 can comprise a rim part (not shown) configured at the end opposite to the bottom part 170. The rim part replicates the rim portion 130 of the container 100, which can be configured to receive a lid.

The stages of a container manufacturing using the method of the present disclosure are shown in Figure 2, Figure 3, and Figure 4.

Firstly, the bottom part 170 of the internal cavity 160 is filled with a fluid plastic material. At least one first fluid injection nozzle 200 introduces the fluid plastic material in the bottom part 170. In an embodiment, single first fluid injection nozzle 200 (as shown in Figure 1) is used which is placed at the centre of the bottom part 170 of the internal cavity 160. In this case, the plastic material is introduced at the central portion of the bottom part 170 (as shown in Figure 2) and then it spreads out towards the periphery of the bottom part 170 (as shown in Figure 3). In another embodiment, a plurality of first injection nozzles are used to introduce the fluid plastic material into the bottom part 170. It is to be noted that the number of injection nozzles 200 to be used and their placement depend upon the size and configuration of the container to be manufactured. For example, to manufacture a relatively small sized container having a circular bottom portion, a single injection nozzle 200 is used which is centrally placed with respect to the bottom part 170. To manufacture a container having a square shaped bottom portion, four first injection nozzles 200 could be used which are placed nearer to the corners of the bottom part 170 of the cavity 160. Further, the sidewall part 180 of the internal cavity is filled with the fluid plastic material using a set of second fluid injection nozzles 210. The second fluid injection nozzles 210 are completely inoperative during filling of the bottom part 170 of the cavity 160 using the first injection nozzle(s) 200. This is shown in Figure 2 and Figure 3, in which the first injection nozzle(s) 200 is operative, whereas the second fluid injection nozzles 210 are inoperative. Further, as shown in Figure 4, in one embodiment when the second fluid injection nozzles 210 are operative, the first injection nozzle(s) 200 is inoperative. In another embodiment, the first injection nozzle could continue to inject material.

The second fluid injection nozzles 210 are placed at the interface between the bottom part 170 and the sidewall part 180 of the internal cavity 160. In an embodiment, the set of second fluid injection nozzles 210 is arranged peripherally with respect to the first injection nozzle 200. The fluid plastic material is introduced in the sidewall part 180 of the cavity 160 when the bottom part 170 of the internal cavity 160 has been completely filled with the fluid plastic material and while the fluid plastic material filled in the bottom part 170 remains in a molten state. When the fluid plastic material is introduced in the sidewall part 180, it blends with the molten plastic material in the bottom part 170 and forms a seamless interface. No visible moulding marks or flow lines are observed at the interface of the bottom portion and the sidewall portion of the final product. It is to be noted that the second fluid injection nozzles 210 can be placed anywhere along the sidewall part 180 of the cavity 160. However, placing the second fluid injection nozzles 210 exactly at the interface of the bottom part 170 and the sidewall part 180 of the cavity 160 avoids formation of the flow lines or moulding marks on the outer surface of the side wall of the final product.

The number of second fluid injection nozzles 210 is determined as per the size and shape of the container to be manufactured. More nozzles 210 results in smooth filling of the sidewall part 180. With an increase in the number of nozzles 200, 210, the number of flow paths also increases which results in smooth fusing of the two streams of the material as the material would still be warmer. Thus, material of the two streams would join in better way and risk of having visible flow lines is also eliminated. In figure 1, an embodiment of a circular container is shown with 3 secondary nozzles is shown, however, another beneficial embodiment to manufacture a circular container would be 5 secondary nozzles arranged in a circular array. Further, the use of separate nozzles to introduce fluid plastic material in the bottom part 170 and in the sidewall part 180 reduces the requirement of high injection moulding pressures. The plastic material introduced in the bottom part 170 has to spread out only up to periphery of the bottom part with slight or no requirement of rising in the sidewall part 180 of the cavity 160. It does not require to rise up to the end of the sidewall part 180 and also not up to the rim portion 130. The material injected at the sidewall part 180 has to spread out only up to the extreme ends of the sidewall part 180. Hence, the cavity 160 can be filled with the material using low injection moulding pressures. Thus, a container with thin walls can be easily manufactured using the method of the present disclosure. Further, reduction in injection moulding pressures also eliminates the need of high mould closing force. Hence, the method of the present disclosure can be executed using low cost moulds and moulding machines. Further, the method can be used in 'in mould label' (IML) processes as it requires low injection moulding pressures. Typically, in IML processes, plastic introduced with high injection pressure can make a hole in the label opposite to the injection nozzle. The IML process can be used both for barrier protection and decorative purposes.

In the current embodiment, the injectors of the set of second injectors are arranged such that the injection flow direction of the injectors is aligned with the extension direction of the sidewall portion. In the current embodiment, the flow from the first injection nozzle 200 is stopped when the bottom part 170 of the cavity 160 is completely filled with the molten plastic material and the fluid plastic material starts rising in the sidewall part 180. As the flow path towards the bottom part 170 is already blocked by the previously injected material, any material injected by the second fluid injection nozzles 210 flows up the sidewall part 180 of the cavity 160. In an embodiment, the fluid plastic material is introduced in the sidewall part 180 of the internal cavity 160 when the molten fluid material introduced in the bottom part 170 of the internal cavity 160 starts rising in the sidewall part 180. Typically, the fluid plastic material is introduced in the sidewall part 180 when the fluid material in the sidewall part 180 has risen at a height up to 2 mm, up to 5mm or up to 10mm from the bottom part 170. In another embodiment, the fluid plastic material is introduced in the sidewall part 180 of the internal cavity 160, when the molten fluid material introduced in the bottom part 170 of the internal cavity 160 passes over the inlets of the set of second fluid injection nozzles 210.

The actuation and de-actuation of the first fluid injection nozzle(s) 200 and the second fluid injection nozzles 210 is controlled by a pre-programmed electronic controller which operates the nozzles 200, 210 on the predetermined filling time or any other suitable parameter.

The present disclosure further envisages a container 100 manufactured by the method elaborated in foregoing paragraphs. The container 100 has a bottom portion 110, a sidewall portion 120 integrally extending from the bottom portion 110, and a top edge defining an opening of the container. The container can have a rim portion 130 at the top edge to receive a lid.

It is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description. For example, the specific materials used and the specific injection moulding procedure have not been described in detail since it is maintained that the person skilled in the art would be able to find suitable materials and suitable processes to manufacture the container according to the current invention.

LIST OF REFERENCE NUMERALS

100- Container

110- Bottom portion of the container 120 - Sidewall portion of the container 130 - Rim portion of the container

150- Injection mould 160 - Internal cavity

170 - Bottom part of the internal cavity 180 - Sidewall part of the internal cavity 200 - First fluid injection nozzle 210 - Second fluid injection nozzle

Claims

1. A method for manufacturing a container, said method comprising the following steps: providing an injection mould having an internal cavity having a bottom part and a sidewall part extending from said bottom part, said internal cavity replicating a shape of said container; filling said bottom part of said internal cavity with a fluid plastic material using at least one first fluid injection nozzle; and filling said sidewall part of said internal cavity with said fluid plastic material using a set of second fluid injection nozzles placed at the interface between the bottom part and the sidewall part when the bottom part of said internal cavity has been completely filled with said fluid plastic material and while the fluid plastic material filled in the bottom part remains in a molten state.

2. The method as claimed in claim 1, wherein the bottom part of said internal cavity is filled with said fluid material by introducing said fluid material via the at least one first fluid injection nozzle placed at the centre of the bottom part of said internal cavity.

3. The method as claimed in claim 1, wherein the fluid plastic material is introduced in said sidewall part of said internal cavity via said set of second fluid injection nozzles when the molten fluid material introduced in said bottom part of said internal cavity starts rising in said sidewall part of said internal cavity.

4. The method as claimed in claim 3, wherein the fluid plastic material is introduced in said sidewall part of said internal cavity via said set of second fluid injection nozzles, when the molten fluid material introduced in the bottom part of said internal cavity passes the inlets of said set of second fluid injection nozzles.

5. The method as claimed in claim 3, wherein the method includes the step of stopping the flow of the fluid plastic material from said first injection nozzle when said bottom part of said internal cavity is filled and said fluid plastic material starts rising in said sidewall part.

6. The method as claimed in claim 3, wherein said fluid plastic material is introduced in said sidewall part via said set of second fluid injection nozzles when the fluid material is filled in said sidewall part at a height up to 5 mm from said bottom part.

7. The method as claimed in claim 1, wherein said bottom part of said internal cavity is filled with the fluid plastic material using a plurality of first fluid injection nozzles, the distance from the centre of the bottom part to the first fluid injection nozzles being smaller than the distance from the centre of the bottom part to the set of second fluid injection nozzles.

8. The method as claimed in claim 1, wherein said second fluid injection nozzles are arranged peripherally with respect to said at least one first injection nozzle.

9. A container manufactured by the method as claimed in claims 1-8.

10. The container as claimed in claim 9, wherein said container has a bottom part, a sidewall part integrally extending from said bottom part, and a top edge defining an opening of said container.