Title: Method for the production of composite containers

Description: This invention is concerned with improvements in and relating to a method of making composite products and more particularly composite containers, that is to say containers formed from a blank of flexible material such as paper, card, or foil shaped to the shape of the container, adjacent edges of the container being seamed by injection moulding.

There is a method of making a composite container by providing a blank having a circular base panel and two side panels each having an edge substantially tangential to the circle of the base, and coupled to the base panel by a web on either side of the point of tangential contact. The side panels are folded about the tangential contact and the webs to position the free edges of each side panel beyond the associated web adjacent the free peripheral edge of the base panel, trapping the so formed blank between a cavity tool and a core tool and seaming the free edges of each side panel to the free edge of the base panel and the juxtaposed edges of the side panels by injection moulding, one of the tools having a recess adjacent each web into which recess excess material represented by the web will be received within a layer of injected material.

The protuberance presented by the excess material which has been pressed into the recess is aesthetically not very pleasing.

According to the present invention there is provided a method of making an article including at least two walls of which one projects from the surface of the other, comprising forming a blank to provide a panel in respect of each wall, forming a slit in the blank in the region between the panels to define a cut-away in at least one wall when the blank is folded about hinge parts integral with each panel remaining at each end of the slit, constraining the folded blank in the folded condition between two mould tools and injecting material into the mould cavity in the region of the cut-away to complete that wall.

In the case of a side panel coupled to a circular base panel to make a frusto-conical container, the arc of the edges of the side panel intersecting the circle of the base panel, the slit may be conveniently on the arc of the edges of the side panel or on the arc of the base panel. The former is preferred preserving as it does the continuity of the side panel and the ends of the slit may be angled or radiused to place those ends on the arc of the base panel. Thereby the hinges are foldable at the periphery of the wall which will be formed by the base panel and will fold about the edge of a core tool. Alternatively, the ends of the slit will be at the intersections of the arcs and a web will be provided beyond each intersection to form a hinge part lying outside the base panel circle. The slit may however be on neither arc and may be rectilinear but again it is preferred that it be within the arc of the edge of the base panel for the reason stated.

In order that the invention will be well understood, there will now be described some embodiments, given by way of example only, reference being had to the accompanying drawing in which:

FIG. 1 is a schematic plan view of a blank for producing a frusto-conical container;

FIG. 2 is a detail section through a part of the blank after folding and seaming, the section being on the line II--II of FIG. 1;

FIG. 3 is a plan view of a presently preferred blank for making a frusto-conical container, and

FIG. 4 is a section in two mutually perpendicular planes through a part of an injection moulding tool and the blank of FIG. 3 modified at the edges.

Referring to the upper half of FIG. 1, the blank which may be of paper, card, foil or other suitable flexible material for making a receptacle, comprises a base panel 1 and two side panels 2. Panel 1 has arcuate free edges 3, in this case circular, and each end of each free edge of panel 1 meets an arcuate free edge 4 of a panel 2 at 5. The arcs of edges 3 and 4 intersect at the meeting point 5. Between the two meeting points 5 associated with each panel 2 is a slit 6 which, in the case shown, lies on the arc of the edge of the side panel 2. The ends of each slit are spaced from the associated meeting points 5 by hinge parts 7.

To make up the receptacle, the side panels 2 are folded relative to the base panel 1 at the parts 7 and the edges 4 are positioned adjacent edges 3. This brings seam edges 8 of each panel 2 adjacent seam edges 8 of the other side panel. The blank is held in the folded condition in a mould, a core tool and a cavity tool of which together define a space corresponding to the base and side wall of the receptacle. In the cavity tool and core tool are channels into which material will flow to form in the finished receptacle a base runner 10 on the outside of base panel 1, an outer peripheral band and support flange 11, an inner base seaming bead 12 and a side seaming bead 13. A lip bead may be included at the open end of the container. The material will enter the channel system at the center of the base panel, will flow along the runner 10 to the peripheral band and flange channel through each slit 6 to the channel defining the inner base bead 12 and thence along the side seam channels and lip channels if provided.

It will be seen that the arrangement of the blank panels and slit avoids the local surplus of blank material and an aesthetically pleasing product is provided. If desired each slit could follow the arc of the base instead of the side panel arc, but it is preferred to provide the slit within the base panel peripheral arc so that on folding, the continuity of the side panels is preserved. Other configurations of seaming channel can also be adopted with a different entry gate position or a plurality of gates. The invention is also applicable to other shapes of product.

The radii of the arcs and the distance of the projection of the free edges of the side panels radially inward of the base panel peripheral arc have been exaggerated for illustration.

The container may be produced on a machine as described in applicant's copending application Ser. No. 405,103, filed Oct. 10, 1973 and now U.S. Pat. No. 3,868,893.

The arrangement above described is satisfactory is the material of the blank has a degree of give.

Each end of the slit 6 should be as near as possible to the arc of the base panel. In practice with a non-yielding material if the edges 4 spring directly from the base panel arc, the ends of the slit cannot lie on the arc of the side panels and reach the base panel arc. On any one generatrix of the core, the material outside the slit must hinge when the blank end panel lies against the end face of a core tool and the side panel is folded to lie against the side of the core tool, to allow the side panel to lie along the generatrix of the core tool. However at each end of the slit 6, material cannot hinge because it is inside the base arc and inside the periphery of the end of the core tool.

This is illustrated by arrow R which is the radius of the base arc and the end of the core tool and R1 the radius on which lies each end of the slit. When the blank is folded on the core tool the material has to hinge, not on the line joining the ends of the radii R, R1 illustrated but on arc R, i.e., the edge of the core tool. Clearly if slit 6 is adopted the material must be such as to give in the region marked X which some materials will do.

When materials are used which will not give enough to allow this to happen without breaking, webs such as shown at 20 may be provided and the slit 6a, here on the arc of the side panel edge, taken to the intersections with the base panel arc, the web providing sufficient material to form an acceptable hinge part. Alternatively each end region such as 21 of a slit may be radiused or angled to bring the end of the slit to a point spaced inward of the adjacent intersection and on the base panel arc.

Instead of a cut lying on an arc of the free edges of a side panel it may be displaced from that arc. Thus, as shown in FIG. 3, which is the presently preferred arrangement of blank, the edges 24 of a side panel are arcuate and the slit is a rectilinear slit 26 extending to the intersection of the arc on which the edges 24 lie and the arc on which the periphery of the base panel lies. Webs 27 provide the material of hinge parts. The base panel has cut outs 29 to accommodate pin gates standing proud of the base of the cavity tool as will appear.

When the blank is folded to form a frusto-conical container, the base panel is no longer circular but has flats or near flats at the slits. There the side panels, when folded, are spaced from the base panel along the slits and, depending upon the position of the radially innermost position of each slit, will depend the extent to which the end of the side panel will, in the folded condition, project beyond the plane of the inner surface of the base panel. This degree is preferably such that when the blank is trapped in between a core tool 32 (FIG. 4) and cavity tool 33, the side panel edge 24 is slightly inwardly deflected and bears on the closed end of the cavity tool.

The material which is to be injected to seam the blank at the now juxtaposed side edges 28 and the edges of the slit 26 and the edges 23 and 24, is injected through a pin gate 35 at the base of each seam channel 32a in the core tool, the base panel 23 being recessed to accept the pin gates as above mentioned. In FIG. 4 each pin gate exit is proud of the closed end of the cavity tool. Thereby the injected material will flow into a base rim recess 36 defined by the core tool and down on to the edge of the side panel and base panel. This will urge those edges against the cavity tool and inhibit flow of material between the blank and the cavity tool. Another particular advantage is that the free edges of the blank are sealed by the injected material, which, if the blank is porous, such as of card, will prevent wicking through those edges.

The base rim recess will allow material to flow round the base panel peripheral margin to seal this to the side panels and to flow into the regions vacated by the blank at the cuts as the blank is folded. The tools may define a lip channel 38 with which channels 32a communicate.

The edges of the blank at the lip of the container may be undulated to improve the anchorage of the injected lip by providing a variable flow path for the injected material between axial and radial limbs of the lip. Such undulations may advantageously be provided at the side seams and the base to side panel seams to improve these seams. Such undulations are indicated at 39 in FIG. 4.

Furthermore the edges at the side seams may be castellated. The undulations suggested for the edges of the side panels relieve stress areas in the injected plastics which might otherwise exist with straight edges while the castellated edges at the side seams give greater bursting strength.

The width of one panel at its edge remote from the base is made fractionally less than the corresponding edge of the other side panel to assist in positioning the blank in a guideway of the moulding machine as described in copending U.S. patent application Ser. No. 405,103 filed Oct. 10, 1973 of Brian Sutch, now U.S. Pat. No. 3,868,893.
Other info:


Inventors: Sutch, Brian Leo Chudleigh (Thames Ditton, EN)

Application Number: 441892
Filing Date: 1974-02-12
Publication_date: 1976-01-06
Assignee: Airfix Industries Limited (London, EN)
Primary Class(es): 264/154 229/4.5, 229/400, 264/251, 264/259, 425/112, 425/129.1
Other Classes:
US Patent Ref:

3154617	Oct, 1964	Schenk et al.	264/328.
3476852	Nov, 1969	Shattuck	425/129.
3511902	May, 1970	Santangelo	264/251.

Other Refs: 45-37,870

Jan, 1970	JA

Primary Examiner: Silbaugh, Jan H.
Assistant Examiner:
Attorney: Scrivener Parker Scrivener and Clarke