Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Patent
1995-06-12
1999-01-05
Davis, Robert
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
228174, 249 79, 249 80, B29C 3304
Patent
active
058559337
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the production of a tool and a corresponding mould which each have at least one inlet and outlet opening and internal channels.
In the injection moulding of plastics mould parts use is made of temperature-controlled tools or moulds consisting of one or more elements each having at least one inlet and outlet opening which are interconnected via at least one channel. Such tools or moulds serve as the "negative" of the plastics end products to be produced. A liquid plastics flow, supplied via a hot channel element (also known as a hot channel plate) from at least one injection moulding nozzle member of a plasticizing unit such as, for example, an extruder is forced via channels into the matching mould cavities. In dependence on the required shape of the end product, the mould cavities have a different geometry as a whole and also as regards the individual wall thicknesses of the plastics mould part.
The liquid plastics is either cured--i.e., chemically cross-linked--via the temperature control medium channel system situated in the moulds, or solidified by the removal of heat by the freezing of the plastics chains. After solidification, the plastics mould part is removed from the tool or mould.
The quality of such plastics mould parts as regards warping, internal stress component, surface quality and time after which the mould parts can be demoulded, depends decisively on the controllability of the heating or cooling process. A spatial course of the temperature control medium channel system and also the temperature of the temperature control medium in the particular zone of the tool or mould are of considerable significance; the channels and cavities should therefore be uniformly heated or cooled, to enable a dimensionally correct plastics mould part free from residual stress to be demoulded in the shortest possible time.
To this end the heat must be evenly introduced into the mould part and evenly removed therefrom over the whole tool or mould cavity surface. In the case of thermoplastic mould parts with single up to very different wall thicknesses this means that, for example, cooling must be performed more intensively in zones with accumulations of material than in zones where less material occurs.
As a rule, tools and moulds consist of single-part or multipart solid steel members purposefully formed from outside with a plurality of bores which approach the wall of the mould cavities except for a predetermined distance. However, such drilled channels, through which a medium can circulate, frequently lead to very inefficient cooling, since the channels can be produced only by straight drilling, so that only a limited influence can be exerted on the mould part to be produced as regards its actual contour and distance from the wall of the mould cavities. FIGS. 4 to 6 show a prior art tool for the production of a plastics mould part. The tool 1 is shown in vertical section in FIG. 4 and mainly consists of a bottom mould 1A, an annular mould 1B and an inner core mould 1C. The cavity enclosed by the three moulds 1A, 1B and 1C forms a mould cavity 2 whose shape corresponds to that of the plastics mould part to be produced.
FIG. 4 also shows an inlet opening 3 and an outlet opening 4 disposed concentrically thereof. They are connected to a channel 5 via which temperature control medium flows through the tool 1. FIG. 5 is a horizontal section through the bottom mould 1A, taken along the line V--V in FIG. 4. It can quickly be seen that the course followed by the channels 5 in the bottom mould 1A is not adapted to the round shape of the mould cavity 2. FIG. 6 is another horizontal section, taken along the line VI--VI in FIG. 4. In this case also an inlet opening 3 and an outlet opening 4 are provided which are interconnected via a channel 5. The channel 5 consists of a number of blind bores 6 which are closed by corresponding plugs 7.
Lastly, FIG. 4 also shows how the core mould 1C can also be constructed in several parts. The individual parts are interconnected via screwed conne
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Davis Robert
Innova Zug AG
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