Plastic article or earthenware shaping or treating: apparatus – Including means advancing continuous length work through...
Patent
1998-03-13
2000-04-18
Pyon, Harold
Plastic article or earthenware shaping or treating: apparatus
Including means advancing continuous length work through...
2642094, 4253261, 4253871, 425392, B29C 4790
Patent
active
060508000
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a sizing sleeve arrangement for controlling the outer diameter of a plastics tube being produced by a continuous tube forming process such as extrusion, or by an expansion process such as that generally described in International Patent Application No. WO 90/02644, wherein the tube at least in the region of the sizing sleeve is under positive internal pressure. The invention also relates to a method of controlling the diameter using the sizing sleeve.
It is known to provide sizing sleeves for tube diameter control with passages allowing the injection of lubricating water between the sleeve and the travelling tube, for example as achieved by a helical channel about the sleeve as described in PCT/FI90/00214 and EP 0 385 285 A2. In the case where the inside of the tube is not pressurized, these sizing sleeves may also have apertures in the sizing sleeve for applying a vacuum to the outside of the tube.
SUMMARY OF THE INVENTION
In one form the invention provides a sizing sleeve for controlling the outer diameter of an internally pressurized plastic tube travelling through the sizing sleeve, the sizing sleeve having an upstream and downstream end relative to the tube travel, including at least two pressurized sizing sleeve portions each having means for injecting fluid under pressure substantially about the circumference of the tube to form a lubricating fluid layer between a sizing sleeve inner surface and the tube, characterised in that the pressurized sizing sleeve portions being axially separated and isolated from each other by a drainage zone.
A further form of the invention provides a sizing sleeve for controlling the outer diameter of an internally pressurized plastic tube travelling through the sizing sleeve, the sizing sleeve having an upstream and downstream end relative to the tube travel, including means for injecting fluid under pressure substantially about the circumference of the tube to form a lubricating fluid layer between a sizing sleeve inner surface and the tube, characterised in that the fluid injection means includes flow stabilizing means which reduces variation in the rate of fluid injection caused by pressure variations in the lubricating layer.
In one preferred form, an inner sizing sleeve member comprises a plurality of coaxial rings arranged end to end, the injection apertures being formed as grooves in one or more end surfaces of the rings. Preferably, the drainage zone has a total drainage aperture area greater than the total injection aperture area of the immediately upstream pressurized portion. The drainage apertures may be formed as a gap between adjacent rings.
BRIEF DESCRIPTION OF THE DRAWINGS
Further preferred embodiments will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a schematic longitudinal cross-section showing a first embodiment;
FIG. 2 is a similar view of a second embodiment; and
FIG. 3 is an elevation, partly in cross-section, of a modular sizing sleeve;
FIG. 4 is an end view of a segment of FIG. 4;
FIG. 5 is a detail of a groove cut into the end of the segment;
FIG. 6 is a partial end view of an alternative modular sizing sleeve;
FIGS. 7A and 7B are part axial cross-sections taken along lines 7A--7A and 7B--7B respectively of FIG. 6;
FIG. 8 is a part axial cross-section of an entry arrangement for the sizing sleeve; and
FIGS. 9 and 10 are axial views of a further embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1, the extruded tube 2 is formed to approximately the desired outside diameter, but requires calibration to ensure conformance to required specifications. While the material of the tube is still sufficiently plastic to be shaped, the tube approaches a sizing apparatus for fine control of the final outside diameter. In the context of the present invention the extruded tube is under positive internal pressure, thus pressing the tube against the cylindrical inner surface of the sizing apparatus. Cooling is applied to the extru
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Chapman Peter Glanville
Cowling Leslie Herbert
Holso Eino
Jarvenkyla Jyri
Wallace Allan Kenneth
Leyson Joseph
Pyon Harold
Uponor B. V.
Vindex Tubemakers Pty. Limited
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