Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Reshaping running or indefinite-length work
Patent
1996-12-17
1999-06-15
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Reshaping running or indefinite-length work
2642888, 2642893, 264310, 425329, 425336, 425392, 425396, B29C 4346
Patent
active
059119390
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for preparing cylindrical surfaces, for example the surfaces of tubes or rods, and in particular to apparatus for processing a plastics tube or rod which has an initially smooth external wall to produce a tube or rod which has an external wall formed with annular grooves.
A tube of this type is particularly suitable for use as a bend limiting tube for sheathing optical fibres, and the structure and use of such a tube is described in my international patent application, publication number WO 93/09457.
It is known from GB-A-O 896 163 to corrugate a thin-walled aluminium tube, to grip a cable core running through the tube. This corrugating can be done by passing a plain walled tube containing a cable core through a corrugating head.
For the purposes of the present invention, there is no restriction on the end use to which the tube or rod may be put. Although this specification describes particularly the preparation of a tube surface, it will be obvious to the skilled man that a rod surface could be prepared in the same way.
According to the present invention, there is provided apparatus for forming parallel grooves in the outer wall of a smooth-bore tube, the apparatus comprising a grooving roller mounted adjacent a passage through the apparatus, the roller having a helically extending ridge formed on the circumference thereof, the ridge extending into the passage and the roller being mounted for rotation about an axis inclined to the passage such that the ridge, where it extends into the passage, runs at right angles to the axis of the passage, means for, in use, rotating the roller about a tube in the passage, and feed means for drawing the tube from the passage under tension so as to stretch the tube as the grooves are formed in the tube outer wall.
The term 'ridge' used in this specification extends to any formation which is raised above a surface of the grooving roller, to indent the surface of a cylindrical object in the passage.
By constructing the groove-forming ridges, and by inclining the roller in this way, it becomes possible to continuously form a series of annular grooves in the surface of a tube as it travels through the apparatus.
There may be more than one helically extending ridge formed on the surface of the grooving roller. Where there is only one grooving roller, each ridge must extend through an arc of length at least equal to the circumference of the cylindrical surface.
It may be possible to provide more than one grooving roller and, for example, three grooving rollers could be provided around the passage. In this case, each roller could form one-third of the circumferential length of each groove. In practice however each roller would form more than one-third of the circumference so that the individually formed groove segments would overlap and properly merge into one another. Where there are a number of grooving rollers, it is no longer necessary for each ridge to have a circumferential length at least equal to the circumference of the cylindrical surface.
It is not intended that the grooves should be formed by cutting of the tube wall material; rather that the grooves should be formed by compressing and to an extent redistributing the material of the tube wall. The cross-sectional profile of the ridges therefore preferably is of an arch-like shape, with the apex of the arch having a radius of about 0.3 mm minimum. In a preferred form, the arch shape is a gothic arch shape.
The passage through the aperture is preferably defined in part by the cylindrical faces of two back-up rollers mounted on axes parallel to the axis of the tube passage, and with their circumferences tangential to the edge of the passage. The grooving rollers and two back-up rollers are preferably spaced 120.degree. apart around the passage. The back-up rollers preferably have smooth outer surfaces. Where there are three grooving rollers as discussed above, the back-up rollers can be replaced by the second and third grooving rollers, with the additional grooving rollers being set
REFERENCES:
patent: 3323339 (1967-06-01), Mattil
patent: 3692889 (1972-09-01), Hetrich
patent: 3818735 (1974-06-01), Grob et al.
patent: 4043161 (1977-08-01), Toma et al.
patent: 5473723 (1995-12-01), Stockman et al.
Eashoo Mark
Heitbrink Jill L.
Miniflex Limited
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