WO1989000917A1

WO1989000917A1 - A fibre reinforced tube element and a method for its manufacture

Info

Publication number: WO1989000917A1
Application number: PCT/FI1988/000121
Authority: WO
Inventors: Olof Sundell; Rolf JERNSTRÖM; Reijo Fredlund
Original assignee: NETTEC Oy AB
Current assignee: NETTEC Oy AB
Priority date: 1987-07-28
Filing date: 1988-07-25
Publication date: 1989-02-09
Anticipated expiration: 1990-01-28
Also published as: FI873285A0; AU2135788A; FI873285L; FI873285A7

Abstract

A fibre reinforced tube element and a method for its manufacture, provided with a wall constructed of a reinforcement layer (2) helically and partially overlappingly wound around a longitudinal axis of the tube element (1), which layer consists of reinforcement fibre yarns extending in an axial direction of the tube element and being embedded in a hardened plastic material (8). In order to construct the tube element with different wall thicknesses and bending strengths in separate sections of the tube element, the turns (4) of yarn in the reinforcement layer are wound with variable overlapping so that the reinforcement layer overlaps more in areas (A) of the tube element requiring a greater bending strength than in areas (B) requiring a smaller bending strength.

Description

A fibre reinforced tube element and a method for its manufacture

The present invention relates to a fibre re- inforced tube element, especially a pole, provided with a wall constructed of a reinforcement layer heli¬ cally and partially overlappingly wound around a longitudinal axis of the tube element, which layer consists of reinforcement fibre yarns extending in an axial direction of the tube element and being embedded in a hardened plastic material.

It is previously known to manufacture fibre re¬ inforced tube elements, such as tube culverts, flag staffs and the like, the wall of which is constructed of a reinforcement layer consisting of reinforcement fibre yarns extending in the axial direction of the tube element and being embedded in a hardened plastic material. The inside of the tube element can be en¬ tirely or partially filled with a core, on which the reinforcement layer is stationarily arranged.

US-Patent 4 089 719 (Fl-Patent 56 502) dis¬ closes a device and describes a method for the manu¬ facture of tube elements by winding a mat of rein¬ forcement yarns helically and partially overlappingly around a core in order to form a tubular reinforcement layer. The reinforcement yarns are embedded in a hard- enable plastic material so that after the hardening of the reinforcement layer a continuous reinforced wall of even thickness is obtained for the tube element. If such a tube element with a reinforced wall of even thickness is used as a pole for distribution of electricity or for telecommunication, the thickness of the reinforcement layer must be chosen according to the maximum wall thickness required by the tube ele- ment in order to be able to withstand the bending strains such a pole will be subjected to. The maximum bending strength is required at the section of the tube element situated immediately above the ground surface when the pole is erected in its place. The need of bending strength decreases thereafter grad¬ ually towards each end of the tube element. Though the manufacturing method according to said US-Patent is extremely simple and advantageous, a tube element with a wall of even thickness manufactured in this way causes the disadvantage that the wall of the pole be¬ comes thicker than necessary at the sections distant from said thickest tube section, the consequence of which is a waste of reinforcement and plastic mate¬ rial. To avoid this disadvantage, it is known from

US-Patent 3 820 573 to construct a tube blank with a conical wall of even thickness, so that the maximum cross section and the maximum bending strength are achieved at a desired section of the tube blank. The reinforcement layer is arranged on a conical core, which remains under the reinforcement layer.

A substantial disadvantage of a tube element manufactured by means of such a method is that the re¬ quirement for conicity makes it impossible to manufac- ture tube elements continuously in endless succession. Each particular tube element must instead be manufac¬ tured on separate conical cores, the length and coni¬ city of which are adapted to the purpose of use.

A further disadvantage of a conical tube ele- ment used as a pole for distribution of electricity or for telecommunication is that it will be more diffi¬ cult to use pole climbers meant for normal cylindrical wooden poles and impossible to utilize components and other equipments developed for cylindrical poles. The intention of the present invention is to provide a tube element avoiding the disadvantages men¬ tioned above and having a desired variable wall thick¬ ness, though the wall has a substantially cylindrical basic form. This is achieved by means of a tube ele¬ ment, characterized in that the reinforcement layer is wound with variable relative overlapping so that the reinforcement layer overlaps more in areas of the tube element requiring a greater bending strength than in areas requiring a smaller bending strength.

The invention is based on the idea that it is possible to change the bending strength of the wall and to maintain at the same time the cylindrical basic form of the tube element by varying the overlap of the reinforcement layer. The tube element of the invention is especially suitable to be used as a pole for dis¬ tribution of electricity and for telecommunication, because the bending strength of the tube element is correct at desired sections of the pole and the tube element in spite of this has a practically cylindrical form, which again makes it possible to use pole climb¬ ers as well as accessories and equipments meant for cylindrical poles.

It is preferable that the reinforcement layer has a cylindrical inner surface and is arranged on a tubular core, preferably consisting of a heat insulat¬ ing material. Such a core prevents too great a differ¬ ence in temperature between the inside and the outside of the tube element in winter circumstances, which substantially reduces the risk of ice formation on the outside of the tube element and thus makes it easier to climb on the pole.

The invention also relates to a method of manu¬ facturing a fibre reinforced tube element, according to which method - around a core is helically wound a reinforce¬ ment layer partially overlappingly in an axial direc¬ tion of the core, which layer consists of reinforce¬ ment yarns extending in the axial direction, - the reinforcement layer is embedded in a har- denable plastic material, and

- the reinforcement layer as well as the plas¬ tic material are hardened to form a continuous tube wall. The method is characterized in that the rein¬ forcement layer is wound around the core with variable overlap so that the reinforcement layer is wound more overlappingly in areas of the tube element requiring a greater bending strength than in areas requiring a smaller bending strength.

The method is based on the idea that it is pos¬ sible to provide even a cylindrical core with a rein¬ forcement layer of variable wall thickness in a simple way by varying the overlap during the winding. A cy- lindrical core makes it possible to continuously feed an endless core to have a reinforcement layer wound around the core and to provide in this way a con¬ tinuous process, in which the overlap is varied by changing the feeding speed and/or the rotary speed of the core depending on the bending strength required at separate sections of the core length. Consequently, it is possible to manufacture tube elements of different length in a continuous process.

In the following, the invention will be de- scribed more closely referring to the enclosed drawings, in which

Figure 1 shows an axial section of an embodi¬ ment of a tube element according to the invention,

Figure 2 shows a cross section of the tube ele- ment along the line II-II in Figure 1, Figure 3 shows schematically an axial section of a portion of the wall of the tube element on an en¬ larged scale, and

Figure 4 shows schematically a process for the manufacture of a tube element by means of the method according to the invention.

Figures 1 and 2 show a tube element 1, the wall of which is formed of a helically wound reinforcement layer 2 and an underlying tubular core 3. In this em- bodiment, the reinforcement layer consists of an UV- durable polyester reinforced by glas fibres and the core consists of hard urethane.

The core 3 has a cylindrical outer mantle surface 3a and the reinforcement layer a cylindrical inner surface 2a, correspondingly. The thickness of the reinforcement layer varies from one end of the tube element to the other so that the maximum wall thickness is achieved at a distance from one end of the tube element corresponding to the ground level, when the tube element is dug into the ground and the tube element is used as a pole for electric and tele¬ phone lines. The wall thickness decreases gradually towards both ends.

As shown in Figure 3, the reinforcement layer 2 is constructed of overlapping turns 4 of substantially parallel reinforcement yarns wound helically around the core and extending in the axial direction of the tube element in the reinforcement layer. The degree of overlap increases from the left to the right from 60 % to 90 % and decreases thereafter from 90 % to 50 %. Because the degree of overlap influences the bending strength of the reinforcement layer, the maximum bend¬ ing strength of the reinforcement layer will occur within the area A, where seven turns of reinforcement yarn in total are lying upon each other. At the area B for instance, only two turns of reinforcement yarn are lying upon each other, which decreases the bending strength correspondingly.

Figure 4 shows a manufacturing method utilizing a winding device disclosed in US-Patent 4 089 719. According to Figure 4, a mat 5 consisting of parallel glass yarns 6 with spreaded ends is helically wound around a tubular core 3, which is fed in the axial di¬ rection, as indicated by the arrow C, with respect to the winding position of the mat, and rotated around its longitudinal axis, as indicated by the arrow D. The mat of reinforcement yarn provides the core with overlapping turns 4, on which is poured or sprayed by means of nozzles 7 a hardenable plastic material 8, a polyester, which saturates the turns of reinforcement yarn. The wound core thereafter passes through a heat¬ ing device 9 for hardening the plastic material and the reinforcement layer to form a finished tube ele¬ ment. The variable overlap of the turns of reinforce¬ ment yarn shown in Figure 3 is provided simply by changing the feed speeding and/or the rotary speed of the core when winding around certain sections of the core so that the turns of reinforcement yarn overlap more in areas of the tube blank requiring a greater bending strength than in areas with a smaller bending strength. This adjustment of the feeding and/or the rotary speed of the core is indicated by an adjusting element 10. If needed, an internal support tube can be used for the core during the winding of the reinforcement layer or a solid core can be used. It is also possible to wind the reinforcement layer detachably around the core and to remove the core after hardening or to dis- place the reinforcement layer from the core in the manner referred to in US-Patent 4 089 719.

The drawing and the description attached there¬ to are only intended to visualize the idea of the in- vention. As to the details, the tube element and the method for its manufacture can vary within the scope of the claims. The fibre mat used for the reinforce¬ ment layer is provided with such a number of longi¬ tudinal supporting yarns that the transverse fibre yarns in the mat obtain a sufficient support during the winding and that the finished reinforcement layer achieves the strength desired in the peripheral direc¬ tion of the layer.

Claims

Claims :

1. A fibre reinforced tube element, especially a pole, provided with a wall constructed of a rein- forcement layer (2) helically and partially over¬ lappingly wound around a longitudinal axis of the tube element (1), which layer consists of reinforce¬ ment fibre yarns (6) extending in an axial direction of the tube element and being embedded in a hardened plastic material (8), c h a r a c t e r i z e d in that the reinforcement layer (2) is wound with vari¬ able relative overlapping so that the reinforcement layer overlaps more in areas (A) of the tube element requiring a greater bending strength than in areas (B) requiring a sπaller bending strength.

2. A tube element according to claim 1, c h a r a c t e r i z e d in that the reinforcement layer (2) has a cylindrical inner surface (2a) .

3. A tube element according to claim 1, c h a r a c t e r i z e d in that the reinforcement layer (2) is wound around a core (3) fastened to the reinforcement layer, which core preferably consists of a heat insulating material.

4. A tube element according to claim 3, c h a r a c t e r i z e d in that the core (3) has a cylindrical mantle surface (3a) .

5. A method for the manufacture of a fibre re¬ inforced tube element, especially a pole, according to which method - around a core (3) is helically wound a rein¬ forcement layer (2) partially overlapping in an axial direction of the core, which layer consists of rein¬ forcement yarns (6) extending in the axial direction, - the reinforcement layer is embedded in a har- denable plastic material (8), and - the reinforcement layer as well as the plas¬ tic material are hardened to form a continuous tube wall, c h a r a c t e r i z e d in that the reinfor- 5 cement layer (2) is wound around the core (3) with va¬ riable overlap so that the reinforcement layer (2) is wound more overlappingly in areas (A) of the tube ele¬ ment requiring a greater bending strength than in areas (B) requiring a smaller bending strength.

10 6. A method according to claim 5, c h a r a c t e r i z e d in that the overlap of the reinforcement layer (2) is varied by moving the core (3) in the axial direction at a variable speed (C) when the core is rotated at a constant speed (D) .

15 7. A method according to claim 5, c h a r a c t e r i z e d in that the overlap of the reinforcement layer (2) is varied by moving the core (3) in the axial direction at a constant speed (C) when the core is rotated at a variable speed (D) .

20 8. A method according to claim 5, c h a r a c t e r i z e d in that the overlap of the reinforcement layer (2) is varied by varying the length of the reinforcement yarns (6) extending in the axial direction when the core is moved and rotated

25 axially at a constant speed.

9. A method according to claim 5, c h a r a c¬ t e r i z e d in that the reinforcement layer (2) is wound around a tubular core (3) with a cylindrical mantle surface (3a) and fastened to the core by

30 hardening.

10. A method according to claim 9, c h a r ¬ a c t e r i z e d in that a reinforcement layer (2) of parallelly extending fibre yarns (6) is wound

* around a tubular core (3) of cellular plastic, the yarns extending in a longitudinal direction of the core.