GB2304621A

GB2304621A - Mould with interchangeable part for moulding plastics containers

Info

Publication number: GB2304621A
Application number: GB9617536A
Authority: GB
Inventors: Mark Godfrey
Original assignee: Stewart Plastics Ltd
Current assignee: Stewart Plastics Ltd
Priority date: 1995-08-22
Filing date: 1996-08-21
Publication date: 1997-03-26
Anticipated expiration: 2016-08-21
Also published as: GB9617536D0; GB9517140D0; GB2304621A8; GB2304621B

Abstract

A method of manufacturing a plastics container comprising a plurality of elements wherein a first element incorporating a predetermined design is integrally formed with at least a second element, which method comprises plastics filling a mould for said elements, allowing the plastics to set and removing the container from the mould is described wherein the mould comprises at least one interchangeable part 3 corresponding to said first element, which interchangeable part 3 itself incorporates a design corresponding to the predetermined design. The interchangeable part 3 is preferably the peripheral rim of a plant pot or box.

Description

PLASTIC CONTAINERS The present invention relates to improvements in plastic containers and their manufacture, including tooling therefor.

In the manufacture of plastics containers such as food storage boxes and plant pots, it is desirable to incorporate the brand or manufacturer's or retailer's name in the container or its packaging prior to the point of sale. For example, traditionally, flower or plant pots have been designed to include a manufacturer's or distributor's brand name or logo permanently affixed to the base of the pot. Any other logo/brand promotion is presently highlighted using pre-printed adhesive tape or shrink sleeving which comprises the packaging for the pots. However, once this tape or sleeving is removed, the brand/logo is only visible from the underside of the pot. There is therefore a need for brand/logo promotion which can be permanently seen when the pot or other container is being used, or displayed for sale, and which is not removable.

Attempts to move the branding from, for example, the base of a plant pot to its rim (which is visible even when multiple pots are stacked together) by using traditional methods as presently applied to the pot base, would produce an unsatisfactory result. Branded bases or such like are produced by having an interchangeable piece or slug in the mould from which the pot is produced. However, the finish produced by such a procedure is somewhat rough and, if visible, would detract from the overall favourable appearance of a good-quality pot.

The present invention relies on using an interchangeable ring to manufacture the pot's rim.

This results in an etched-looking finish which is far superior to that produced by the use of a slug.

Although it might be possible to brand the rim by means of a slug, the end result would be more embossedlooking and also it would be technically more difficult to achieve (particularly in view of the curved surface at the rim). By using the method of the present invention, it is now possible to design a range of flower or plant pots to meet consumer or trade requirements, since the required brand name may now be effectively incorporated into the design around the outer rim of the product. Depending on customer requirements, this branding or logo may be removed altogether or replaced at will with the customer's own brand name/logo. Of course, the method of the present invention could be applied to other plastic containers, as mentioned hereinbefore.

The present invention therefore provides a method of manufacturing a plastics container comprising a plurality of container elements wherein a first container element incorporating a predetermined design is integrally formed'with at least a second container element, which method comprises plastics filling a mould for said container elements, allowing the plastics to set and removing the container from the mould characterised in that the mould comprises at least one interchangeable mould part corresponding to said first container element, which interchangeable mould part itself incorporates a design corresponding to the predetermined design.

In particular, at least one interchangeable mould part corresponds to a peripheral region of the plastics container. The peripheral region is preferably one having a continuous circumference in cross-section and more preferably the peripheral region is at or towards the mouth of the container.

Preferably, the first container element comprises a plant pot rim, top rim of a plastic box or the like.

Preferably, the second container element comprises a plant pot middle body, box body or the like. In these examples, a third container element may be present which comprises a plant pot or box base. Accordingly, the interchangeable mould part is in the form of an interchangeable ring or rectangular section, respectively. Various rings or rectangular sections (respectively) would be available to correspond to the predetermined design which may, for example, incorporate a brand name or logo.

Preferably, the method is carried out by injection moulding by processes known to those skilled in the art. Such processes can use any material which is suitable for injection moulding and preferably polypropylene, polyethylene, polystyrene, styrene acrylonitrile (SAN) or acrylonitrile butastyrene (ABS); especially preferred is when the plastics is polypropylene.

The present invention therefore further provides an injection-mould tool for manufacturing a plastics container which container comprises a plurality of container elements wherein a first container element incorporating a predetermined design is integrally formed with at least a second container element, characterised in that the mould tool comprises at least one interchangeable mould part corresponding to said first container element, which interchangeable mould part itself incorporates a design corresponding to the predetermined design.Accordingly, the injection-mould tool of this invention comprises a plurality of tool elements wherein a first tool element incorporating a design corresponding to a predetermined design is associated with at least a second element, characterised in that the first tool element corresponds to a peripheral region incorporating the predetermined design of a plastics container.

Preferably, for manufacturing a plant pot, the injection-mould tool is provided with an interchangeable cavity ring which can incorporate the customer's own brand name or logo.

The present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-section through an injection mould tool according to the invention; Figure 2 is a plan view of the top of an injection mould tool according to the invention; Figure 3 is a longitudinal cross-section through a prior art injection mould tool (one-part cavity); Figure 4 is a longitudinal cross-section through a prior art injection mould tool (two-part cavity); and Figure 5 is a side elevational view of a plant pot produced in the injection mould according to figures 1 and 2.

Referring first to Figures 1 and 2: Each flower or plant pot mould is designed so that the cavity is divided into three sections: a base insert (1), a middle body cavity insert (2) and an interchangeable cavity ring (3). Each section is made from fully hardened, tempered and ground tool steel. Each section has its own water cooling channel (4) which enables the pots to be produced at a faster rate than they could be produced in the absence of water cooling. The interchangeable cavity ring (3) is held in position within and abutting the middle body cavity insert by retaining screws (5).

Each interchangeable cavity ring (3) can be assembled and disassembled while the mould is mounted in the injection moulding machine. Removal and replacement is carried out in the following way: Water cooling connection pipes (4) are removed. Cavity ring retaining screws (5) are unscrewed and the ring (3) removed using jacking screws. A soft cloth is used to clean the replacement cavity ring mounting face which is then inserted and aligned into position on a location dowel. The retaining screws (5) are replaced and tightened; and then the water connection pipes (4) replaced.

Apart from the use of an interchangeable cavity ring (3), this mould design further differs from any previously designed flower or plant pot injection mould tool in that it comprises a three part cavity. Prior art tools can be seen in Figures 3 and 4; these designs have always incorporated logo or brand requirements on the base of the cavity, by means of an interchangeable slug which fits into the cavity base. The slug corresponds to the logo or brand design.

Otherwise, the injection moulding equipment of the present invention is used in the conventional fashion to produce plant pots having an etched-like finish to the branded rim (Figure 5). In this example, the injection moulding technique uses a hydraulicallyoperated machine with a single screw plasticising unit (not shown) in which the raw material or polymer is fed along a heated cylinder by the rotation of a large screw. The combination of the external heaters around the cylinder together with the shearing and mixing action of the screw delivers a molten material (polypropylene) to the front of the cylinder.

This material is then injected into the mould (Figures 1 and 2) using hydraulic force. The molten material inside the mould is then left to solidify and, while this process is taking place, the screw rotates to refill the plasticising unit. Once the plastic has solidified, the mould opens and ejects the product (Figure 5); the mould then closes and the process starts again.

Claims

1. A method of manufacturing a plastics container comprising a plurality of container elements wherein a first container element incorporating a predetermined design is integrally formed with at least a second container element, which method comprises plastics filling a mould for said container elements, allowing the plastics to set and removing the container from the mould characterised in that the mould comprises at least one interchangeable mould part corresponding to said first container element, which interchangeable mould part itself incorporates a design corresponding to the predetermined design.

2. A method according to claim 1 characterised in that at least one interchangeable mould part corresponds to a peripheral region of the plastics container.

3. A method according to claim 1 or claim 2 characterised in that at least one interchangeable mould part corresponds to a plant pot rim or a top rim of a plastic box.

4. A method according to any of claims 1 to 3 characterised in that at least one interchangeable mould part is adapted to be assembled or disassembled while the mould is mounted in a moulding machine.

5. A method according to claim 4 characterised in that at least one interchangeable mould part is adapted to be held in position in the mould by retaining screws.

6. An injection-mould tool suitable for use in a method according to claims 1 to 5, which tool comprises a plurality of tool elements wherein a first tool element incorporating a design corresponding to a predetermined design is associated with at least a second element, characterised in that the first tool element corresponds to a peripheral region incorporating the predetermined design of a plastics container.

7. A tool according to claim 6 characterised by comprising a three-part cavity.

8. A tool according to claim 7 characterised in that the three-part cavity comprises a base insert, a middle body cavity insert and an interchangeable cavity ring.

9. A plastics container when manufactured by a method according to any of claims 1 to 5 or by using a tool according to any of claims 6 to 8.

10. A plastics container according to claim 9 which is in the form of a plant pot or a box having a design incorporated into a top rim thereof.