POLE AND METHOD FOR ITS MANUFACTURE

POTEAU ET SON PROCEDE DE FABRICATION

English 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.

French Abstract

Cette invention se rapporte à un poteau (1), par exemple du type mât porte-drapeau, qui est constitué par un matériau fait essentiellement d'un premier composant, par exemple du verre, et d'un second composant, par exemple un polymère. Ces deux composants entrent dans le matériau comme fibres composites préfabriquées formée par deux composants, sous la forme d'une bande (2) de mèches discontinues. Le polymère est un polymère thermoplastique, par exemple du propylène, et ce poteau est fabriqué à partir de ces fibres composites sous contrainte thermique, ce qui ramollit le polymère et amalgame ainsi les fibres composites, pour que celles-ci, après refroidissement, adoptent une forme fixe. On peut fabrique ainsi par exemple un mât porte-drapeau qui est moins coûteux que les mâts porte-drapeau traditionnels par exemple en polymère renforcé par des fibres de verre et qui en même temps possèdent des propriétés aussi bonnes.

Claims

8
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

9
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.

Description

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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.

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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.

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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.

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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

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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

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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.

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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.
35

Representative Drawing