Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Including restriction upstream of shaping orifice and...
Patent
1998-03-24
2000-08-08
Pyon, Harold
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Including restriction upstream of shaping orifice and...
425465, B29C 4716
Patent
active
060992905
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an apparatus in the form of a tool comprising a flow channel.
REVIEW OF THE RELATED ART
No method has been known so far in which to change the width of the melt strand during extraction by modification of the geometry of the flow channel in the tool.
Various types of apparatuses as described above have been known. They are used especially in the field of plastics processing in flow channels for thermoplastic melts for the possibility of modification of flow channel resistance. EP 0 367 022, DE 35 30 383 A1, DE 44 00 069 C1 and DE-AS 12 31 412 teach extrusion dies in which to change the flow channel height.
These known solutions comprise a more or less thick, solid, one-piece metal wall which can be deformed by adjusters pressing on the wall from the rear. They work only as long as the solid wall, during deformation, does not exceed the range of linear elasticity because they depend on the fact that upon return motion of the adjusters, the wall will take precisely its original initial position. Because of the comparatively thick wall required in these apparatuses for reasons of solidity, the possibilities of uniform adjustment of the wall over the entire width of the flow channel (overall adjustment) are restricted as well as the locally defined adjustment of a small portion of the wall (relative adjustment).
DE-OS 23 05 877 describes a limitation of a flow channel which consists of several thin individual sheets lying one upon the other over their full surfaces and consequently possesses higher flexibility. But this flexibility is purchased by this solution abandoning the important criterion of absolute leak-tightness towards the fluid flowing in the flow channel, because mobility of all the individual sheets in the marginal areas is required for adjustment. To this end, the marginal areas of the sheets reach into grooves which are located between the two halves of the flow channel body. The surface pressure necessary for leak-tightness in these marginal areas cannot be applied, because it would not allow any motion of the sheets relative to the flow channel halves.
Consequently, solutions offering a wide adjusting range accompanied with absolute leak-tightness of the flow channel have not been disclosed in the known apparatuses of the generic type. The known apparatuses neither offer the possibility to put a method into practice in which a melt strand is forced through an absolutely leak-tight tool channel, two independent adjusting systems, which are integrated in the tool and act on a wall of the flow channel, serving to modify the thickness of the melt strand during melt discharge either in its entirety or only locally at certain places or to change both simultaneously, nor to change the width of the melt strand during extraction by changing the geometry of the flow channel in the tool.
Since apparatuses of the generic type for both entirely or locally adjusting the height of a flow channel of a great adjusting range by means of two independent adjusters acting on a wall of the flow channel have not been available so far, methods are not known either by means of which in this way to change a melt strand during extraction.
SUMMARY OF THE INVENTION
The invention relates to a flow channel with a width or circumference-to-height ratio greater than 10, and a mechanism for the absolutely leak-tight limitation of a flat flow channel. The mechanism insures that, by means of externally accessible adjusters, at least one flow channel wall can be adjusted in its overall position to the largest extent possible, i.e., uniformly over the entire width, as well as locally, i.e., in strictly defined portions over the width, in relation to the opposite demarcation of the flow channel.
The invention further relates to a method, using another embodiment of the invention, for continuously discharging a melt strand by means of a tool having at least one adjustable wall, in which, during the discharge of the melt, the height of the entire flow channel is adjusted by a fi
REFERENCES:
patent: 3850568 (1974-11-01), Bartha et al.
patent: 3884611 (1975-05-01), Anderson et al.
patent: 4518343 (1985-05-01), Seiffert
patent: 5788998 (1998-08-01), Gross
Leyson Joseph
Pyon Harold
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