CA2269548A1

CA2269548A1 - Pole and method for its manufacture

Info

Publication number: CA2269548A1
Application number: CA002269548A
Authority: CA
Inventors: Thomas-Peter Thogersen
Original assignee: Individual
Current assignee: DANOMAST GT GLASFIBER AS
Priority date: 1996-10-14
Filing date: 1997-10-08
Publication date: 1998-04-23
Also published as: NO991730D0; EP0930965A1; NO991730L; WO1998016376A1; WO1998016376A8; PL332630A1; AU4550297A

Abstract

A pole (1), for example a flagpole, is made of a material which is mainly made up of a first component, such as glass, and a second component, such as a polymer. The two components enter into the material as premade composite fibres formed by both components, in the form of a web (2) of rovings. The polymer is a thermoplastic polymer, for example polypropylene, and the pole is made of the composite fibres under heat stress which softens the polymer and thereby joins the composite fibres so that they, after cooling, assume fixed shape. In this way, for example a flagpole which is less expensive than a conventional flagpole of for example glass-fibre reinforced polyester and which, at the same time, has just as good properties, can be manufactured.

Description

,~ ' CA 02269548 1999-04-13 PCT/T7Y.97/~~431 Method for manufacturing a hollow pole The invention concerns a method for manufacturing a hollow pole of composite fibres which each consists of an inner core of glass and an outer coating of a thermoplastic polymer which is surrounding the core.
A typical example of such poles are flagpoles which earlier were normally made of wood. However, in the recent many years, wood as material for flagpoles has largely been replaced by other materials. A material which has grown quite popular is glass-fibre reinforced polyester which is characterised by a number of outstanding properties.
Flagpoles made of this material, in practice known as glass-fibre flagpoles, are thus light and at the same time very strong. They have a smooth, bright surface which is weather-resisting and dirt repelling, and unlike wooden flagpoles, they do not require recurrent maintenance such as painting or lacquering.
The flagpoles can be constructed in different ways, but normally the polyester in the pole is reinforced by several layers of tube-shaped fibres in the form of webs or mats which lie rather close together.
Depending on batch sizes, more or less mechanical or manual methods of manufacturing the flagpole can be adopted. For manual laying up, the glass fibre webs, which in advance has been drenched with polyester, is thus laid round a mandrel.
Each layer is pressed by a groove roller to compress the web and press out the air in the web, before the next layer is laid up.

PCT/'".97/e431 Manufacturing a flagpole of glass-fibre reinforced polyester is therefore rather difficult and demanding work.
In addition to this, the still not cured polyester gives off unhealthy vapours. The responsible authorities therefore demands that effective installations to exhaust the vapours and filter off unhealthy elements before the vapours are discharged into open air are installed at the working area.
A pole, such as a flagpole of glass-fibre reinforced polyester or of a similar fibre reinforced polymer, will be rather expensive due to the above-mentioned production-related circumstances.
t The object of the invention is to provide a method of the type mentioned in the opening paragraph for manufacturing a hollow pole which is less expensive to manufacture than a pole made of glass-fibre reinforced polyester or a similar fibre reinforced polymer and which, at the same time, has just as good properties.
The novel and unique features according to the invention whereby this is achieved, is the fact that the method is comprising using composite fibres consisting of an inner core of glass and an outer coating of a thermoplastic polymer which is surrounding the core, preforming a large number of said composite fibres into a fibermaterial in form of e.g. rovings, mats, webs or fabric, and forming the pole of said preformed fibrematerial around a mandrel under thermal stress.
TrJhen the polymer is a thermoplastic polymer, the material of a pole is recyclable and can thereby be utilised again. Thereby an advantage is furthermore obtained in that discarded poles and poles with manufacturing faults will no longer pollute the environment to the same extent as poles of e.g. glass-fibre reinforced polyester which are virtually imperishable.

PcT~nx.y~~o~431 The dependent claims 2 - 4 show advantageous methods according to the invention.
The invention will be explained in greater detail below, where only exemplary embodiments are described with reference to the drawing, in which fig. 1 is a perspective view of a flagpole according to the invention, fig. 2 a - g are perspective views of successive process stages of a first embodiment of the method according to the invention of manufacturing the flagpole shown in fig. 1, fig. 3 a - c are perspective views of successive process stages of a second embodiment of the method according to the invention of manufacturing the flagpole shown in fig. 1, and fig. 4 a - c are perspective views of successive process stages of a third embodiment of the method according to the invention of manufacturing the flagpole shown in fig. 1.
Fig. 1 shows, diagonally from the end and in perspective, a flagpole 1 according to the invention. The flagpole is, in this case, made up of a number of tube-shaped webs 2 which transversely lie close together. The web is woven from rovings each consisting of a large number of fibres. Each fibre is a composite fibre of two components, respectively glass and a thermoplastic polymer, such as polypropylene.
The flagpole can be manufactured in different ways as described in details in the following.

PCT/DT:97 / e431 Fig. 2 a - g show a first method according to the invention of manufacturing a flagpole. In this method, the flagpole is thus constructed round a rigid mandrel 3 of for example aluminium.
At its ends, the mandrel has journals 4 for rotatable suspension in a pedestal (not shown).
In fig. 2a, a web 5 is wound round the mandrel 3 until a layer 6 having mainly the diameter of the finished pole is formed.
The web 5 is of the above-mentioned type of composite fibres of glass and a thermoplastic polymer respectively, in the following, the polymer is assumed to be, as an example, polypropylene.
In fig. 2b, a film 7 of a thermoplastic polymer, such as acrylic, is wrapped round the formed composite fibre layer 6.
This film 7 is dyed in the wanted colour of the finished pole.
In fig. 2c, a flexible plate 8 is laid round the film 7.
During the further processing, the surface of the composite fibre layer 6 with the film 7 will be formed as an impression of the surface of the plate 8 facing the composite fibre layer. Normally, flagpoles of an even, smooth surface are wanted, the surface being dirt repelling and easy cleanable, and the plate 8 must then have a correspondingly even, smooth surface.
In fig. 2d, an air permeable mat 9 is laid round the already laid layers 6, 7, 8, 9. Since the mat is air permeable, it allows confined air being evacuated.
In fig. 2e, the layers 6, 7, 8, 9 are concluded with a vacuum tube 10 being put round them for compressing a11 the layers 6, 7, 8, 9 firmly round the mandrel when the tube is connected to a vacuum source (not shown). Thereby, it is effectively PCT/C.':97/~~431 ensured that the finished flagpole will assume the fixed form of the mandrel.
In fig. 2f, the mandrel 3 with the layers 6, 7, 8, 9, 10 is 5 placed in a furnace 11 at a temperature of e.g. 200~C. The mandrel stays in the furnace for about 5 minutes during which the two thermoplastic polymers, in this example polypropylene and acrylic respectively, soften and assume the shape of the mandrel, simultaneously the composite fibres of the web 5 are joined whereby a solid, coherent layer 5 is formed, said layer is furthermore joined with the acrylic film 7.
The mandrel 3 with the layers 6, 7, 8, 9, 10 is then taken out of the furnace and cooled to a temperature where both the polypropylene and the acrylic transform into the solid phase, and finally, the different layers 8, 9, 10 and the mandrel 3 are removed from the now solid and joined layers 6, 7 which form the in fig. 2g shown finished flagpole 1.
Fig. 3 a, b, c show a second method according to the invention of manufacturing a flagpole. In this method, the flagpole is constructed round a flexible mandrel 12 of for example thermostable silicone rubber. The mandrel 12 is via a tube 13 with a valve 14 connected to a compressed-air source (not shown). By opening the valve 14, the flexible mandrel 12 is put under pressure.
In fig. 3a, a web 14 is wound round the mandrel 12 until a layer 15 having mainly the diameter of the finished pole is formed. The web is of the same kind as the web 5 shown in fig.
2 a-g of composite fibres of glass and polymer, respectively.
In fig. 3b, the mandrel 12 with the composite fibres 15 is placed in a mould 16 of for example aluminium. The mould 16 consists, in this case, of two halves 16 a, b which in fig. 3b are closed round the composite fibre layer 15 and the mandrel PCT/~=;97/e431 12. The valve 14 is now opened so that the flexible mandrel 12 expands and thereby presses the composite fibre layer 15 to abut against the inside of the mould chamber which has a shape corresponding to the shape of the finished flagpole.
The mould 16 is, in advance, heated to for example 150~C. When the mould is closed and the flexible mandrel 12 put under pressure, the mould is heated further to a temperature of 200~C
and kept at this temperature for a sufficient period of time, for example 5 minutes, until the polymer softens and thereby assumes the shape of the mould chamber, at the same time as the composite fibres of the web 14 are joined.
At the end of the standing time in the furnace, the mould is cooled to about 150~C at which point the plastic polymer transforms into the solid phase. The mould is then opened and the mandrel removed when the pressure has been released.
In fig. 3b, the finished flagpole 17 is taken out of the open mould 16.
Fig. 4 a, b, c show a third method according to the invention of manufacturing a flagpole.
In this case, a plate is formed, as shown in fig. 4a, said plate consisting partly of web 19 which is of the same kind as the web 5 shown in fig. 2 a - g of composite fibres of glass and polypropylene respectively, and partly of an substratum in the form of a dyed acrylic-film 20 with an even, smooth surface.
The plate 18 may be formed under pressure at a temperature of for example 200~C and with a standing time of 5 minutes during which the polypropylene softens and the composite fibres of the web 19 are joined, simultaneously the acrylic-film 20 is joined with the composite fibres.

PCT/~'_'.97/~~431 The plate 18 is then cooled to 80~ - 120~C and curved, as shown in fig. 4a with the acrylic substratum at the outside, to a jacket 21 round a rigid mandrel 22 having the shape of the wanted cavity of the finished flagpole.
Finally, the two long sides 23 a,b of the wrapping 21 are joined by a weld 24 by means of a welding gun 25 after which the finished flagpole is pulled off the mandrel. The flagpole is now the colour of the acrylic-film and has its even, smooth surface.
It is to be noted that the joining of the long sides can also 1' be done by means of other joining methods, for example bonding or hot melting, just as the seam can be a lap weld instead of a butt joint.
In a11 the examples of the methods shown in the drawing and described above, it is assumed that webs of composite fibres is used in the manufacture. Within the scope of the invention, for example mats of composite fibres or composite fibres in the form of rovings can also be used depending on the circumstances.
When flagpoles are mentioned, it is further to be understood as an example, since the concept of the invention can also be applied to the manufacture of any kind of poles.

Claims

1. Method for manufacturing a hollow pole (1) of composite fibres each consisting of an inner core of glass and an outer coating of a thermoplastic polymer surrounding the core, characterized in that the method comprises that a large number of said composite fibres is preformed into a fibermaterial (2;5;14;19) in form of e.g. rovings, mats, webs or fabric, and that the pole is formed of said preformed fibrematerial around a mandrel (3;12;22) under thermal stress.

2. Method according to claim 1, characterized in that said preformed fibrematerial (5) is wound in a layer (6) round a mandrel (3) which has the shape of the cavity of the pole (1), that a film (7) of a thermoplastic polymer, such as acrylic or polypropylene of the wanted colour of the pole (1), is wound round the formed layer (6), that a flexible plate (8) which, at least on one of the sides, has a surface which corresponds with the finish of the pole, is laid up around the polymer film (7) with said side facing the film, that an air permeable mat(9)is laid up around the flexible plate (8), that a vacuum tube (10) which is connected to a vacuum source is wrapped around the mat (9), thereby compressing the remaining layers (6;7;8;9;) firmly around the mandrel (3), that the unit, formed in this way, is heated for a sufficient period of time in for example a furnace, that the heated unit is subsequently cooled, and that the mandrel (3), the vacuum tube (10), the mat (9) and the flexible plate (8) are removed.

3. Method according to claim 1, characterized in that said preformed fibrematerial (14) is wound in a layer (15) around an elastomeric mandrel (12) of for example silicone rubber, that the wrapped elastomeric mandrel (12) is placed in a cavity, corresponding to the wanted configuration of the pole (1), in a hot mould (16), that the elastomeric mandrel (12) is put under pressure by for example air, that the wrapped elastomeric mandrel (12) is kept in the hot mould (16) for a predetermined period, that the wrapped elastomeric mandrel (12) is cooled in the mould (16), that the mould (16) is opened and the mandrel (12) is removed when the pressure has been released in said mandrel (12).

4. Method according to claim 1, characterized in that a plate (18) is formed, under thermal stress, of said preformed fibrematerial (19), said plate having mainly the same thickness as the wanted wall thickness of the pole (1) and the same length as the finished pole (1), that the plate during cooling is folded round a mandrel (22) which has the shape of the cavity of the pole (1), so that the long sides of the plate are brought close together or to touch each other, that the long sides are joined by means of for example bonding or welding, and that the mandrel (1) is pulled out.