Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – Female mold type means
Patent
1988-08-01
1989-11-21
Hoag, Willard
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
Female mold type means
249 661, 249 83, 249161, 425127, 425547, 425556, 425588, 425436R, B29C 4540, B29C 4514, B29C 3344
Patent
active
048818844
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an array of moulding tools, each adapted to mould a plastics closure onto a metal can end.
DESCRIPTION OF THE PRIOR ART
British Pat. No. 2073646 describes a method of moulding a plastics plug into an aperture defined by a metal can end. The metal can end is clamped between an upper mould and a lower mould and plastics material is injected into mould cavities to form a plastics plug having a ring pull portion on one side of the can end and a sealing annulus on the other side. In order to prevent flash emerging from the mould cavities to render the mouldings unsightly or unusable, it is necessary to clamp the can end material tightly. However, it is in the nature to common sheet metals to vary by plus or minus 7% in thickness so that a mechanical clamping system actuating a moulding press will clamp thinner can ends less tightly than thicker can ends. This problem is increased if the moulding press incorporates an array of moulding tools distributed across a press platen because the first tools to clamp upon a thick metal will hold tools with thin metal therein apart.
SUMMARY OF THE INVENTION
According to the present invention there is provided apparatus for injection moulding plastics closure elements into apertures in the central panels of a plurality of can ends, said apparatus comprising, a first mould tool; a second mould tool; means effective to bring the mould tools together to clamp on opposed surfaces of each central panel and thereby define a mould cavity enclosing a margin of panel material around the aperture and spanning both sides of said aperture; and a passageway in at least one of the mould tools to permit injection of plastics material into said mould cavity, wherein, the first mould tool includes a plurality of cavity defining mould portions each slidably guided in a respective bore in said first mould tool and resilient support means in each bore to urge each said mould portion towards the second mould tool; and the second mould tool includes a plurality of mould inserts each defining a cavity to cooperate with a cavity of a mould position in the first tool, so that upon closing of the first mould tool to the second mould tool any mould portion closing upon a relatively thick can end panel will be urged, by the cooperating insert, to retract into its bore and permit clamping of a relatively thin can end panel between another mould portion and its cooperating mould insert, and sealing of all the moulds will be established before plastics material is injected into the mould cavity.
The clamping means may be resiliently supported on a spring or stack of Belville washers.
Alternatively, the clamping means may be resiliently supported on pressurised fluid, such as oil or compressed air.
DESCRIPTION OF THE DRAWINGS
Various embodiments will now be described by way of example and with reference to the accompanying drawings in which:
FIG. 1a is a diagrammatic sectional side view of a simplified injection moulding apparatus showing the problem to be overcome;
FIG. 1b is a sectional side view of a defective moulding produced by the apparatus of FIG. 1a;
FIG. 1c is a sectional side view of a satisfactory moulding produced by the apparatus of FIG. 1a;
FIG. 2 is a sectioned side view of a first embodiment of apparatus for moulding a plastics plug into a can end;
FIG. 3a is a plan view and FIG. 3b a sectional side view of the can end as fed to the apparatus of FIG. 2 or FIG. 5;
FIG. 4a is a plan view and FIG. 4b is a sectioned side view of the can end after moulding of a plastics plug therein;
FIG. 5 is a sectioned side view of a second embodiment of apparatus for moulding a plastics plug into the can end of FIGS. 3a and 3b.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
FIG. 1a shows a simplified apparatus for injection moulding a flanged plug of plastics material into an aperture in a sheet material. The apparatus comprises an upper tool 1 and a lower tool 2 which may be moved by a press (not shown) to clamp sheer material therebetw
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Hoag Willard
MB Group plc
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