NZ272568A - Producing tube of corrugated material by helically winding extruded plastic strip - Google Patents

Description

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Complete Specification Filed: Class: Publication Data:.... ...JLLJM.ffl96 P.O. Journal No: Divided from Patent Application No. 257388 filed on 30 June 1994 NEW ZEALAND PATENTS ACT, 1953 272 y Umior the provisions of Regw 23 (1) ths ^ffv^yethaic^.

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InftMs N.Z. P^TVf OTICE 1 3 JUL 1995 \ RECEIVED No.: Date: COMPLETE SPECIFICATION APPARATUS FOR PRODUCING CORRUGATED TUBE ^fWe, T0Y0 CHEMICAL CO., LTD., a corporation of Japan, of 13-1, Dai 2-chome, Kamakura-shi, Kanagawa 247, Japan hereby declare the invention for which-Wwe pray that a patent may be granted to sac/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page la) Apparatus for Producing Corrugated Tube This invention relates to an apparatus far producing a corrugated tube of synthetic resin. More particularly, it relates to an apparatus for producing a corrugated tube in which the cross-sectional shape of outer circumferential surface of the tube is corrugated and which exhibits sufficient flattening strength and especially high molding stability and high durability.

Various proposals have hitherto been made for an apparatus for producing a corrugated tube of synthetic resin so that the outer circumferentail surface of the tube has a corrugated cross-sectional profile. For example, there is an apparatus comprising a roller assembly made up of plural rollers forming an imaginary cylinder, the rollers being each provided with plural rings of the same size, and being rotated about their own axes at equal speed, the rollers being arranged parallel to one another so that the axes of the rollers are on the circumferential surface of the imaginary cylinder and the axial directions of each of the rollers being circumferentially inclined while being parallel to one another, a die for continuously supplying a strip of synthetic resin in a molten state from the lateral side onto the periphery of the roller assembly and a driving motor for 27 2 5 68 continuously rotating the rollers at equal^peed. The construction and configuration of such apparatus is described and claimed in our NZ Patent No. 208302. There is also an apparatus (Japanese Patent Publication No. 62-60261(1987)) which further comprises a pressure roller profiled .for meshing with the profile of the outerwall surface of each roller for fixing the shape of the strip of synthetic resin, means for cooling the synthetic resin as it is shaped to a tubular profile as it is moved along the outer periphery of the imaginary cylinder and forming means for forming a smooth cylindrical-shaped synthetic resin on the inner side of the corrugated tube for providing a double-walled structure. apparatuses, as the strip of synthetic resin is wound spirally and advanced along the axis of the roller assembly while being cooled and cured, it is not considered that the strip itself is contracted* in size due to cooling. Since the—— rings formed on each roller are of the same size and arrayed at an equal interval on the roller, the synthetic resin strip is actually being cured under conditions in which the strip is pulled outwardly along the shape of each convexed ring. The result is that, as the strip of synthetic resin progresses axially along the roller assembly, the strip tends to be detached from the valley portions between the convexed rings to detract from molding stability, accuracy and durability of the ultimate corrugated tube.

However, with the above-described Besides, with the above-described 272 ^ W Q - 3 - apparatus, although each roller of the roller assembly is rotated at equal speed, a difference in the circumferential speed of about 10 to 45% is produced between the circumferential speed at the apex of the convexed portion and 5 that in the recessed interstices between neighboring convexed portions of each roller, so that longitudinal creases (internal strain) are produced between the convexed portions and the recessed valley portions of the wall surfaces of the corrugated tube, with the result that the produced ultimate 10 corrugated tube is lowered in durability, such as impact strength or pressure resistance.

It is a preferred object of the present invention to provide an apparatus for producing a corrugated tube which is capable of preventing a strip of synthetic resin from being 15 detached from the rollers due to contraction in size and which is superior in durability, such as impact strength or pressure resistance.

It is another preferred object of the present invention to provide an apparatus for producing a corrugated tube which 20 is superior in durability, such as impact strength or pressure resistance and in which longitudinal creases (internal strain) between the convexed portions and the valley portions thereof are not formed.

According to the present invention there is provided 25 apparatus for producing a corrugated tube comprising a roller assembly composed of plural roller means, each being rotatable at equal speed, said roller means being arrayed on a cylindrical surface of an imaginary cylinder formed by the roller assembly, roller supporting means mounted axially opposite said roller assembly for rotatably supporting said roller means, means for continuously supplying a warm synthetic resin strip to an outer 9S0403,ptopeiMcsy,33770.div,3 circumferential surface of said roller assembly from a lateral side thereof, and driving means for rotating said roller means at equal speed, each axis of said roller means being inclined in a circumferential direction of the roller assembly so that each axis of the roller means is not parallel to the axis of the imaginary cylinder while remaining parallel to the surface of the imaginary cylinder, plural rings being provided along the axial direction of each of said roller means, each of said rings being offset along the axis of each roller means with respect to the corresponding ring on adjacent roller means so that the rings form a helix, a follower ring being provided at a recessed valley portion between neighbouring rings, the circumferential speed of said follower ring being the same as that of the outer circumferential surface of the rings, said apparatus further comprising a pressure roller having a convexed shape mating with a convexed shape of said roller means for fixing a shape of said strip wound and advanced in a helix.

In an embodiment of the invention, the cross-sectional shape of the circumferential surface of the tube coincident with the convexed shape of the plural roller means is corrugated. The inner cylindrical synthetic resin forming means for forming a smooth cylindrical synthetic resin on the inner side of the corrugated tube wall surface, that is on \ the inner peripheral surface of the imaginary cylinder, may be provided for providing a dual wall for the corrugated tube. Besides, cooling means may be provided within each roller means and within the inner cylindrical synthetic resin forming means for cooling the strip of synthetic resin as it is wound.

In an embodiment of the invention, it suffices if each 9SM05.p:\operUc»y.53770.div,4 27251 axis of the roller means is circumferentially inclined relative to the axis of the roller assembly at an angle of inclination which allows the strip of synthetic resin to be moved continuously in the axially extending direction of the 5 roller assembly for continuously producing the spiral-shaped tube. In addition, each axis of the roller means may be circumferentially inclined relative to the axis of the roller assembly, while at the same time each axis of the roller means may be equally inclined toward the central axis of the 10 roller assembly so that the diameter of the imaginary cylinder is decreased gradually in the axially extending direction. By inclining the roller means so that the imaginary cylinder is decreased gradually in diameter, it becomes possible to prevent the molding stability and 15 accuracy from being lowered due to the contraction caused by cooling of the strip of synthetic resin. At least one of the roller supporting means may be provided with inclination angle adjustment means for adjusting the angle of inclination of the roller means.

The synthetic resin employed for producing the corrugated tube is preferably thermoplastic resin, such as polyethylene, polypropylene or polyvinyl chloride. Incidentally, the strip of synthetic resin may be a flat strip when supplied from the supplying means or may be 25 supplied in the corrugated form mating with the corrugations of the roller means.

The follower ring may be rotated responsive to the circumferential speed of the apex portions of the ——: 950405,p:\operiJuy.53770.div.5 272568 rings plays the role of preventing longitudinal creases (internally as strains) from occurring between the convexed portions and valley portions of the wall surface of the corrugated tube due to the roller means making up the roller 5 assembly being rotated at an equal speed to produce a difference in the circumferential speed on the order of about to 45% between the apex point of the ——ring and the valley portions between the rings for improving durability such as impact strength or pressure resistance. There is no 10 particular limitation to the follower ring if it is capable of being rotated at the circumferential speed of the strip of synthetic resin at the apex point of the convexed ring so that when the strip travels in contact with the convexed portions of the roller means and the valley portions, the 15 strip may be rotated at an equal circumferential speed at the apex point and at the valley portion without regard to the rotational speed of the shafts of the roller means. Thus, the follower rings may be formed as rings freely rotatably mounted on the valley portions via bearings or the like. 20 Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:- Fig. 1 is a schematic side elevational view showing an apparatus for producing a corrugated tube according to an 25 embodiment of the present invention.

Fig. 2 is an enlarged view showing a roller having — rings shown in Fig. 1. 930403,p:\opa\k»y,S3770.div,6 272 Fig.3 is a schematic back-side view showing the apparatus shown in Fig.1.

Fig.4 is a front view showing a supporting plate in the apparatus shown in Fig.1, with only an arrangement of the 5 rollers being schematically shown for ease of understanding.

Fig.5 is a schematic view showing perspectively the inside of a part of a roller assembly in the apparatus shown in Fig.1.

Fig.6 is a schematic side elevational view showing 10 an apparatus for producing a corrugated tube according to a modified embodiment of the present invention.

Fig.7 is an enlarged schematic partial cross-sectional view of a roller shown in Fig.6.

Fig.8 is a schematic cross-sectional view taken ^-5 along line C-C in Fig. 7.

Fig.9 is an enlarged schematic view of a roller having convexed rings and follower rings provided in valley portions between neighboring convexed rings, with the pitch between neighboring convexed rings and the diameters and the 20 widths of the convexed rings being decreased gradually along the axial direction.

In Fig.l, 1 is an apparatus for producing a 7 272 corrugated tube comprised of a supporting frame 2, a disk-shaped supporting plate 4 opposed to the supporting frame 2, nine rollers 3ai to 3i making up a roller assembly 3, which is arranged along an imaginary circle between the supporting 5 frame 2 and the supporting plate 4 and which substantially forms a single rotating shaft body, a motor 10 for rotating the rollers 3a to 3i at equal speed and a die 8 for supplying a strip of synthetic resin A to the roller assembly 3.

The half portion of each of the rollers 3a to 3i 10 towards the supporting frame 2 is provided with seven annular rings 9 on its outer peripheral surface, as shown in Fig.2. The pitches Px to P6, the diameters Qx to Q7 and the widths Rx to R7 of the — rings 9 are selected so as to be gradually decreased from the supporting frame 2 towards the ^L5 supporting plate 4 in Fig.l so that the ratios P6/Pi» Q7/Qi and R7/R1 amount to 0.9. The half portion of each of the rollers 3a to 3i towards the supporting plate 4 is a smooth cylinder. Since the changes in the pitches, the diameters and the widths of the —rings shown in Fig.l are only small in contrast to the size of the entire apparatus, they are shown with substantially the same size different from actual sizes.

The supporting plate 4 is mounted on the distal end of a hollow base shaft 5 passed through the inside of the supporting frame 2. Shaft portions 6, 7 of each roller 3a to 25 3i is rotatably supported in bearings. Each shaft portion 6 passed through the supporting frame 2 is adapted for being 8 rotated at equal speed under the driving force of the motor 10 by interconnecting, by means of endless chains 15, 16, each sprocket loaded on each of the rollers 3a to 3i, as shown in Fig.3, a sprocket 12 loosely mounted on a shaft 11 set on the supporting frame 2, and a sprocket 14 mounted on a speed-reducing unit 13 connected to the motor 10. A sprocket 17 is employed for tension adjustment of the endless chain 15. By such arrangement, when the sprocket 14 of the speed-reducing unit 13 is rotated by the motor 10, the sprockets of the rollers 3a to 3g are rotated by the movement of the endless chain 15 and, with the rotation of the endless chain 15, the endless chain 16 is moved to rotate the sprockets of the rollers 3a to 3i to cause the rotation of the rolls 3a to 3i at equal speed.

Each shaft portion 7 passed through the supporting plate 4 is rotatably supported by being passed through each elliptically shaped bearing 7a (see Fig.4) capable of adjusting the angle of inclination of the roller shaft. If the shaft portions 7 are supported at the radially outermost positions of the imaginary cylinder 18 as shown in Fig. 4, the roller assembly 3 is supported in its entirety in parallel with one another relative to the axial direction x of the base shaft 5 with an inclination angle of x-y. If each shaft portion 7 is supported by the elliptically shaped bearings 7a at the radially innermost positions of the imaginary cylinder 18, the roller assembly 3 may be supported so that the 9 2 £ <=?' U Qj diameter of the imaginary cylinder 18 shown in Fig.4 is gradually decreased in the direction proceeding from the supporting frame 2 towards the supporting plate 4. By supporting the shaft portions 7 so that the diameter of the 5 imaginary cylinder 18 is decreased gradually, it becomes possible to prevent the spirally wound strip of synthetic resin A from being detached from the valleys of the rollers 3a to 3i as a result of contraction due to cooling of the strip A.

In Fig.l, 19 is a pressure roller having a corrugated profile corresponding to the seven rings 9 on the rollers 3a to 3i for pressing the strip of synthetic resin A discharged from the die 8 onto the peripheral surface of the roller assembly 3 for fixing the shape of the strip A.

The pressure roller 19 is rotatably mounted externally of the roller assembly 3 constituting the imaginary cylinder. 20 is a guide roller for guiding the strip A as it is discharged onto the roller assembly 3. The guide roller 20 is mounted externally of and parallel to the roller assembly 3.

In Fig.5, 21 is a die for discharging a strip of synthetic resin B which forms a smooth cylindrical surface which is to become the inner wall surface of the corrugated tube. The die 21 is connected to a mandrel 22 mounted inside of the base shaft 5, and is mounted at a mid portion within the inside of the roller assembly 3 so that the strip of synthetic resin B is supplied to the smooth portions of the rollers 3a to 3i.

Within the inside of the rollers 3a to 3i, there is provided a known unit, not shown, for circulation of cooling water for cooling the strip of synthetic resin A which is wound spirally as it is discharged from the die 8.

The process for producing a corrugated tube using the above-described apparatus 1 is hereinafter explained.

Referring to Fig.l, the strip of synthetic resin A discharged from the die 8 is continuously discharged via the guide roller 20 onto the outer periphery of the rollers 3a to 3i, while at the same time the motor 10 is driven in rotation for rotating the rollers 3 to 3i at equal speed matched to the rate of supply of the strip A. In this manner, the strip A is supplied sequentially to points m4, m3, m2 and ml on the outer periphery of the roller assembly 3 shown in Fig.l.

After one round of the strip A is wound around the outer periphery of the roller assembly 3, that portion of the strip A which has made a complete round is partially overlapped with a portion of the strip A to be subsequently supplied in the similar manner, and is advanced by virtue of the inclination of the rollers 3a to 3i to form a complete turn of the helix. The strip A is moved past the pressure roller 19 in the vicinity of the roller 3i so that the strip A is fixed in a corrugated shape by the cross-sectional shape of the roller assembly 3 in cooperation with the contour of the pressure roller 19. When the strip A reaches the last ring 9 11 provided on each of the rollers 3a to 3i, the strip of synthetic resin B is discharged from the die 21 shown in Fig.5 and is supplied to the smooth portions of the rollers 3a to 3i, as the strip B is advanced gradually and caused to be continuously bonded to the inner surface of the strip A wound in the helical form to define a cylindrical inner surface of the corrugated tube. The strip B is advanced in the direction of extension of the supporting plate 4 by taking advantage of the inclination of the shafts of the rollers 3a to 3i for continuously producing a corrugated tube having a double-wall structure comprising a corrugated outer wall and a cylindrical inner wall.

The wave-shaped outer wall of the corrugated tube continuously produced in this manner is cured and contracted by being cooled by cooling means, not shown, provided within the inside of the rollers 3a to 3i. Since the pitches, the diameters and the widths of the. rings 9 provided on the rollers 3a to 3i are reduced in the direction proceeding from the supporting frame 2 towards the supporting plate 4 at the rates related to the rate, of contraction of-the various portions of the strip A in the apparatus 1 as shown in Fig.2, the wave-shaped outer wall of the corrugated tube is continuously formed without the strip A being disengaged from the valley portions between the last convexed rings 9 and the last but one convexed rings 9 of the rollers 3a to 3i without regard to the contraction of the strip A caused by cooling. 12 279 P) o Consequently, the corrugated tube produced is improved in molding shape stability and accuracy while being superior in durability. The molding shape stability and accuracy may be further improved by inclining the axial direction of each of the rollers 3a to 3i so as to gradually reduce the diameter of the roller assembly 3 in addition to the adjustment of the pitches, diameters and widths of the—; : rings.

Referring to Fig.6, 60 is an apparatus for producing a corrugated tube according to a modified embodiment of the present invention. The apparatus 60 includes nine rollers 63a to 63i in place of the roller assembly of the apparatus 1 shown in Fig.l, wherein the rollers 63a to 63i are each provided with eight rings 62 at the same pitch.

Incidentally, the die 2 for forming the smooth inner surface shown in Fig. 5 is not installed. The embodiment shown in Fig.6 is otherwise the same as that shown in Fig.l, so that various parts or components of the present embodiment are denoted by the same reference numerals and the corresponding description is not made.

Fig.7 shows the rollers 63a to 63i shown in Fig.6 by a partially enlarged cross-sectional view, and Fig.8 is a cross-section taken along line C-C in Fig.7.

Each of the rollers 63a to 63i is formed with — rings 62 of the same shape and size. On a roll substrate 64 in each valley portion between neighboring rings 62, each follower ring 61a is rotatably mounted 13 27256 8 via dry bearings 61b and a positioning fixture 61c fixed by a fitting 65 without regard to the rotation of the roll substrate 64. Cooling means, not shown, for circulating cooling water in a manner well-known per se, is provided > internally of each of the rollers 63a to 63i.

The method for producing a corrugated tube by the above-described apparatus 60 is hereinafter explained.

Referring to Fig.6, the strip of synthetic resin A discharged from the die 8 is continuously discharged onto the 10 outer periphery of the rollers 63a to 63i via the guide roller . Simultaneously, the motor 10 is driven in rotation for rotating the rollers 63a to 63i at equal speed matched to the supply rate of the strip A. In this manner, the strip A is supplied sequentially to points m4, m3, m2 and ml on the outer ^15 periphery of the roller assembly 63 shown in Fig. 6. After one round of the-strip A is wound around the outer periphery of the roller assembly 63, that portion of the strip A which has made a complete round is partially overlapped with a portion of the strip A to be subsequently supplied for making the 20 round in the similar manner, and is advanced by virtue of the inclination of the rollers 63a to 63i to form a complete turn of the helix. The strip A is moved past the pressure roller 19 in the vicinity of the roller 63i so that the strip A is shaped in a corrugated shape by the cross-sectional shape of 25 the roller assembly in cooperation with the contour of the pressure roller 19. 14 27256.

On the other hand, as the strip A is moved as described above, when the strip A is supplied to both the ■.-.r rings 62 and the follower rings 61a provided adjacent to the -——. :•••"• rings of each of the rollers 63a to 63i, the strip portion at the follower rings 61a are rotated at the fastest circumferential speed at each apex of the convexed rings 62 without regard to the rotation at the axial center of each of the rollers 63a to 63i. Since the follower rings 61a are rotated at a speed corresponding to the circumferential speed at the apexes of the — rings 62 due to transfer of rotational force of the strip A without regard to the rotation of the rollers 63a to 63i, it becomes possible to dissolve the internal strain of the strip A due to the difference in the circumferential speed between the apex of the ring 62 and the roll substrate 64 with the result that the longitudinal creases usually produced between the rings 62 and the valley portions with the use of known rollers not provided with the follower rings may be prevented from being produced and consequently a spiral-shaped corrugated tube having excellent durability may be produced by employing the rollers 63a to 63i provided with the follower rings 61a.

In Fig.9, 90 is a roller in which the pitches Px to P6 , diameters Qx to Q7 and widths Rj^ to R7 of the rings 92 are gradually reduced, similarly to the rollers 3a to 3i shown in Fig.2, and in which follower rings 91 like the follower ring 61a rotatably mounted via dry bearings 61b on a positioning fixture 61c shown in Fig.7 is mounted in the valley portions between the convexed rings 92.

By employing the roller 90 in place of the rollers 5 in the apparatus 1, 60 shown in Figs.l or 6, it becomes possible to prevent the strip of synthetic resin from being detached from the roller surface due to contraction of the strip to produce a corrugated tube which is excellent in molding shape stability, accuracy and durability such as 10 impact strength or pressure resistance and which is not susceptible to longitudinal creases, which are manifested as internal stresses, between the rings and the valley portions between the ■ rings. 16

Claims (5)

WHAT WE CLAIM IS:

1. An apparatus for producing a corrugated tube comprising a roller assembly composed of plural roller means, each being rotatable at equal speed, said roller means being arrayed on a cylindrical surface of an imaginary cylinder formed by the roller assembly, roller supporting means mounted axially opposite said roller assembly for rotatabfy supporting said roller means, means for continuously supplying a warm synthetic resin strip to an outer circumferential surface of said roller assembly from a lateral side thereof, and driving means for rotating said roller means at equal speed, each axis of said roller means being inclined in a circumferential direction of the roller assembly so that each axis of the roller means is not parallel to the axis of the imaginary cylinder while remaining parallel to the surface of the imaginary cylinder, plural rings being provided along the axial direction of each of said roller means, each of said rings being offset along the axis of each roller means with respect to the corresponding ring on adjacent roller means so that the rings form a helix, a follower ring being provided at a recessed valley portion between neighbouring rings, the circumferential speed of said follower ring being the same as that of the outer circumferential surface of the rings, said apparatus further comprising a pressure roller having a convexed shape mating with a convexed shape of said roller means for fixing a shape of said strip wound and advanced in a helix.

2. An apparatus according to claim 1 further comprising inner cylindrical wall forming means for forming a smooth cylindrical wall of synthetic resin on an inner peripheral surface of said imaginary cylinder for providing a dual wall for the corrugated tube. - 18- 27 2 5 6

£. An apparatus as claimed in any one of the preceding claims wherein each axis of the roller means is further inclined toward a central axis of said roller assembly at an equal angle so that the diameter of said imaginary cylinder is gradually decreased along the axially extending direction.

4. An apparatus as claimed in any one of the preceding claims further comprising inclined angle adjustment means in at least one of the roller supporting means for adjusting an angle of axial inclination of said roller means.

5. An apparatus as claimed in Claim 1 substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS DAY OF A. J. PAB' ^