Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common...
Reexamination Certificate
1998-11-12
2001-03-20
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
C425S562000, C425S564000
Reexamination Certificate
active
06203305
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hot-runner coinjection distributor block arrangement of several block parts for a hot-runner plate of a multiple hot-runner coinjection tool for injection moulding multi-layered mouldings of plastic.
Such multiple hot-runner coinjection tools for injection moulding mouldings of plastic materials have been known for a long time and are applied essentially with the manufacture of premouldings, as are required by the drinks industry for their so-called PET bottles in large quantities. Increasingly there exists the requirement to design these premouldings multi-layered, in order for example to provide these with recycled material or air impermeable blocking layers. At the same time unusually high demands are made on the mould tools, since with the processing of PET, PEN and their copolymers, as well nylon, EVON or similar blocking layer material, their differing temperature and transport behaviour must be taken into account independently of one another.
The high demands on the controllable temperature guidance in hot and pressure loaded tool parts has led to more complicated tools which are expensive, are prone to damage and are expensive to maintain.
DESCRIPTION OF THE PRIOR ART
Therefore for example a simple design has been suggested in EP-0'480'223 with which instead of a one-piece hot-runner distributor block with separate feed channels, there are applied two hot-runner distributor blocks arranged behind one another which in each case carry one of the plastic components. With this, the various materials, also with a different temperature, may be fed to the nozzles in a simple manner. Between these hot-runner distributor blocks separated from one another there are applied disc-like muffs through which plastic material and a nozzle closure needle are passed and which permit a mutual lateral displacement of the two distributor blocks in this region, inasmuch as this displacement is created by a differing temperature expansion of the individual hot-runner distributor blocks. Furthermore, between the hot-runner distributor block on the head plate side and the head plate, further muffs are provided through which the respective nozzle closure needles project and which occlude a centrally arranged feed channel in a pressure tight manner. These muffs space the block on the head plate side and the head plate in order to separate these thermally from one another and are to accommodate the axial pressure caused by the temperature expansion.
Unfortunately it has been shown that the provided means for compensating the differing temperature expansion of the two hot-runner distributor blocks do not meet the mechanical demands with multiple tools with more than 8 nozzles, in particular with 48 or 96 nozzles. With these highly equipped multiple tools the tension force produced by the thermal expansion is multiplied by the number of nozzles present and leads to the fact that the individual blocks lying plane-parallel to one another on account of their lateral fixation bend open and leak at the connection locations of the respective feed channels, or that the lateral retaining screws cannot withstand the increased mechanical loading.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a hot-runner coinjection distributor block arrangement for injection moulding multi-layered mouldings and for a multitude of injection nozzles, with which differing material components which may comprise different melting and processing temperatures, may be treated without leakage and with low wear. This distributor block arrangement is to be maintenance friendly and thus formed inexpensively.
According to the invention this object is achieved by a distributor block arrangement according to claim
1
, and in particular by a distributor block arrangement which consists of several block parts. These block parts are slidingly supported within a hot-runner plate and are mounted displaceably against one another. For this between the individual block parts there are provided sliding intermediate pieces and between the block part on the head plate side and the head plate there are incorporated movably mounted support elements, wherein between these support elements and the head plate there is provided at least one spring element which spaces the support element in the cold operating mode from the head plate. The distance produced by these spring elements permits a thermal expansion for the whole distributor block arrangement, without leading to unacceptable tension conditions. The closure force necessary for the sealing of the individual block parts or intermediate pieces is produced by this spring element independently of the respective operating temperature.
With this distributor block arrangement simultaneously 48 or more multi-layered mouldings of plastic may be manufactured, without at the same time there occuring leakage problems or premature occurrences of wear. In particular the thermal expansion which is increased many times by these highly equipped multiple tools may be accommodated and it may be avoided that the individual blocks lying plane-parallel to one another are bent open, or that their lateral retaining screws shear. Further advantageous features of the invention are deduced from the dependent claims or auxiliary claims.
In particular the individual block parts may be heated independently of one another and the intermediate pieces and support elements are manufactured from a poor heat-conducting material. Furthermore the intermediate pieces and support elements are provided with a peg-shaped projection in order to control and advantageously so influence the mutual positioning of the individual block parts that the bores for the needle of the needle closure system and the feed channels are not essentially displaced against one another under thermal loading.
REFERENCES:
patent: 4043726 (1977-08-01), Tsunemoto et al.
patent: 4588367 (1986-05-01), Schad
patent: 5094603 (1992-03-01), Gellert
patent: 5200207 (1993-04-01), Aksulrud et al.
patent: 5891381 (1999-04-01), Bemis et al.
patent: 5894023 (1999-04-01), Schramm et al.
patent: 2035159 (1969-07-01), None
patent: 8709724 (1987-09-01), None
patent: 480223 (1992-04-01), None
Fernandez Luis
Hofstetter Otto
Heitbrink Tim
Nath Gary M.
Nath & Associates PLLC
Novick Harold L.
Otto Hofstetter AG, Werzeug-und Formenbau
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