Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
1999-12-21
2001-07-24
Nguyen, Nam (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C425S553000, C425S567000, C425S572000, C425S588000, C425S810000, C264S106000, C264S163000
Reexamination Certificate
active
06264459
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention lies in the field of manufacturing disc-like plastic objects, for instance information carriers such as CDs. A two-fold injection moulding unit is known for this purpose. This injection moulding unit comprises two injection moulds coupled mechanically to each other. Via a multiple hot-runner beam the unit is fixed rigidly against a front plate by means of bolts such that the injection buses debouching with a passage in the respective mould cavities are enclosed between the two, such that the central hole of a disc-like object is formed by retracting a punch. This requires an expensive and time-consuming construction, wherein movable wedges are placed behind the punch to hold the punch in place when it is loaded with a high injection pressure during the injection of plastic.
It is comparatively simple to form the central hole in a disc by means of a punch. The drawback hereof is that this requires an injection bush having to be moved aside for the purpose, which is awkward because an injection bush is connected by means of bolts to said hot runner beam. This combination will thus have to be able to move during punching and be in fixed position during injection. The injection bushes are guided in a guide formed by a front block. This block is cooled from 120° C. to 50° C. The hot runner temperature amount to about 350° C. As a consequence the hot runner therefore expands much more than the front block and, because the injection bushes are fixed to the hot runner with bolts, they will be clamped fixedly on one side by expansion of the hot runner. It is an object of the invention to provide a solution to this problem. A further object of the invention is to provide an injection moulding unit enabling a simpler and less expensive structure.
SUMMARY OF THE INVENTION
The invention now provides an injection moulding unit comprising at least two injection moulds for manufacturing in each case successive disc-like objects, in particular disc-like information carriers such as CDs, which injection moulds each comprise:
at least two mould parts which are mutually displaceable between a closed position, in which they bound a mould cavity, which mould cavity is connected to a pressure line for carrying heated plasticized plastic under pressure into this mould cavity, and an opened position in which a disc-like object can be removed; and
punching means for punching a central hole from a disc-like object, which punching means comprise a cylindrical part forming part of the one mould part and having a leading peripheral edge with a form adapted to the shape of the hole to be punched from a disc-like object, which part is axially movable from and to the other mould part;
wherein the respective pressure lines of the moulds are branches of a feed line and together therewith form part of a collective multiple hot runner, wherein the inlet zone of the feed line is adapted for coupling to the outfeed of a plastic-plasticizing and pressing device;
wherein the outlet zone of each feed line is adapted for coupling to the infeed of an injection bush, the outfeed of which debouches directly into the mould cavity;
wherein the hot runner is coupled by means of spring means to a connecting piece of thermally conductive material, which connecting piece is fixedly connected to the injection bushes; and
wherein tempering means are present for holding the temperature of the connecting piece within predetermined limits.
The hole in the disc-like object is made by means of a punch. The combination of injection bush and hot runner has to move aside for this purpose. This takes place by making use of spring means connected to this combination. In order to prevent the injection bushes becoming jammed in the block when the hot runner beam expands, the invention provides a construction which ensures that the injection bushes are held in place. This takes place by making use of the connecting piece. This connecting piece is fixedly connected to the injection bushes by for instance bolts. The connecting piece must be tempered in order to function properly. This tempering can take place by heat transfer via radiation from the block, heat conduction via the block, by making use of cooling channels in the block, with electrical Peltier elements or other suitable ways of holding the connecting piece at the same temperature as the block, at least within certain tolerance limits.
Heat transfer can also take place via springs placed between the connecting piece and front block, while the connecting piece can be guided in axial direction relative to the front block by means of a central guided pin, which likewise provides transfer.
It is of further importance to shield the heat coming from the hot runner. Use can be made to this end of a plate of insulation material between hot runner and connecting piece. Further use can optionally also be made of for instance a reflective layer, consisting for instance of mirrored aluminium.
The contact surfaces between injection bushes and hot runner can be insulated, for instance by means of ceramic rings.
Forward movement of the hot runner takes place under the influence of the pressure applied by the injection nozzle, i.e. the outfeed of the plastic-plasticizing and pressing device used. It is therefore important that this injection nozzle can move back during punching of the hole in the disc. The backward movement takes place over a slight distance such that the contact with the hot runner beam is maintained. Leakages and air inclusions are hereby effectively prevented.
Essential for the invention is the use of the resiliently arranged hot runner. Also of essential importance is the connecting pieces of thermal material between the injection bushes and the use of tempering means to keep the connecting piece at a desired temperature. It is of further importance that this connecting piece be held in place by for instance a guide pin which can be arranged fixedly in the front block and over which the connecting piece can slide via a fitting. This pin ensures that the injection bushes remain precisely in the middle of their guide. Said tempering of the connecting piece ensures that the injection bushes follow precisely the thermal expansion of the front plate.
Attention is drawn to the European patent EP-B-0 567 682. This publication discloses a double injection mould with only one movable hot runner without further moving components. The combination according to the invention cannot be derived from this older European specification.
The invention will now be elucidated with reference to the annexed figures.
REFERENCES:
patent: 4212624 (1980-07-01), Ando et al.
patent: 4971548 (1990-11-01), Asai
patent: 5238393 (1993-08-01), Kishi
patent: 5648105 (1997-07-01), Shimazu et al.
patent: 5792493 (1998-08-01), Gellert
patent: 0051253 (1982-05-01), None
patent: 0567682 (1993-11-01), None
patent: 05220778 (1993-12-01), None
patent: 07227883 (1995-12-01), None
Axxicon Moulds Eindhoven B.V.
Heckenberg Donald
Nguyen Nam
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
LandOfFree
Multiple injection moulding unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiple injection moulding unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiple injection moulding unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2563816