Modular fiber reinforced plastic poles
The invention relates to poles made from reinforced polymers (Fiber Reinforced Plastics - FRP),
the production process of poles and the use of poles as a modular product.
Reinforced polymers belong to the class of composites, and consist of polymers and reinforcing
glass fibers or other materials (aramid, carbon, etc.) in various forms (yarns, matts, felts, fabrics,
meshes).
The poles are widely used for overhead power distribution lines, for the support f transmission
lines in telecommunications and for various public and private uses (lighting, road signs, camera
support, flag poles, etc.).
The first applications of overhead utility lines, lighting, telecommunications, etc., were made using
wooden poles, because it was easier and cheaper to be produced from tree felling. They also had
the advantage of insulation. For this reason, they were the dominant technology and even today
they still hold the largest share of installed poles in many countries around the world.
Wooden poles, however, have considerable disadvantages due to the nature of wood (natural
product), such as being attacked by insects, microorganisms and the weather conditions.
Therefore, they require impregnation with dangerous pesticides, the use of which is subject to
restrictions (e.g. creosote - DIRECTIVES 98/8/EC, 201 1/71/EU). Wooden poles can also spread
the fire, and when used in power distribution significant current leakages to the ground occur and
reduce the network efficiency. Finally it is a non-industrial product with seasonal production which
is not always predictable, with negative consequences on the availability (need to keep large
stocks) and the price.
For these reasons, alternative pole technologies and materials have been developed such as iron,
reinforced concrete and reinforced polymer (FRP).
- Iron provides higher strength than wood. Iron poles have stable availability and are hollow,
facilitating the passage (lowering) of the cables. However they rust and thus require
protection. Furthermore iron is a good conductor of electricity and its use requires additional
components (e.g. insulators) and special working conditions and precautions in order to avoid
accidents.
- Reinforced concrete provides sufficient strength and a certain degree of insulation, but the
heavy weight of these poles is a problem for their transport and installation. Also the rigid
behavior of the centrifugal concrete poles in car crushes is dangerous (causing serious traffic
accidents). Furthermore, concrete cracks over time and the steel reinforcement is exposed
and rusts.
- Poles made of FRP combine significant advantages such as low weight, concave shape,
resistance against micro-organisms and environmental conditions and reliable availability.
However, their use is limited because of their higher cost, compared to other solutions.
Also in all the above cases (wood, iron, concrete, FRP) the currently existing poles are
manufactured, sold, delivered, transported and installed in their full dimension. This means that the
user doesn't have the potential to purchase and have these poles delivered as individual parts
(modular product) in smaller packaging, and to assemble those on-site (at the installation area),
which would facilitate both their transport - by using a smaller transport mean - and their
installation, making them cheaper.
The present invention relates to poles made of FRP, which consist of individual parts of suitable
shape so that :
a . every single individual part can be produced in industrialized, automatic or semi-automatic,
economical production methods of FRP and
b. the poles can be easily assembled, in a standardized manner by unqualified personnel by using
simple and light tools, according to the manual.
The result of the above design is that the poles of the Invention :
a . firstly, have stable and repeatable (industrial) quality, short production cycle and easy
availability, combined with low production costs, directly competitive against the poles from
other materials, and even lower life cycle cost,
b. and secondly, can be provided to customers (utility companies, contractors or other users)
either as a finished product, i.e. assembled as a single item, or as a modular product, i.e. their
separate individual parts before their assembly, along with the necessary tools and complete
manual for their installation and assembly on site.
Specifically:
The poles of the invention consist of two or more (depending on the total height and the desired
strength) concave (hollow) parts (tubes) of constant cross-section (cylindrical, polygonal, oval, etc.)
which are connected by respective annular joints (connectors) with circumferential grooves on each
side.
The concave parts of constant cross sections (tubes) are shaped to serve the operational needs of
customers in an optimal way (e.g. cross section with grooves for the easy installation of the cable
support fittings, cross section with stiffening ribs, cross section with a channel for cables crossing
etc.). They also have appropriate wall thickness to meet customer requirements in terms of the
mechanical strength and rigidity of the poles.
Each annular joint connects two successive concave cross sections (tubes) and is shaped so that
the one side fits to the upper section and the other side fits to the lower section. The upper side of
the joint has a circumferential groove into which the upper section is inserted snugly and ends.
Similarly the lower side of the joint has a circumferential groove into which the lower section is
inserted snugly and ends. The above design of the joints allows the easy and precise assembly of
the poles with simple means.
Adhesive is applied for the welding of the joints with the concave sections, which may be combined
with mechahical restraint (e.g. screws, pins, cotter pins, rivets etc.), which is either permanent or
temporary (until the adhesive is polymerized) and removable.
The application of the adhesive can be performed by simply spreading into each groove of the joint
before placing the respective tube (concave part) in it. It can also be performed by injecting through
a special applicator, either in the groove of the joint before placing the respective concave part (as
mentioned above), or after the placement of the respective concave part (tube) in the groove of the
joint through an appropriately shaped hole, Which leads the adhesive into the gap, in order to
achieve the welding.
The poles of the invention also have a cap, which fits on the last upper section and is placed on top
of the poles ensuring water tightness. The cap has a circumferential groove at its lower side into
which the last upper section of the pole is inserted snugly and ends.
Furthermore, the poles of the invention may include additional components (rings, inserts, etc.) and
configurations (holes, channels, etc.) according to the user's needs. We indicatively mention,
without limitations, the opening of transverse through-holes to the poles, in which internal
(reinforcing and guiding) tubes are applied and adhered. These holes are used for passing
components, screws and cables (for example, near the top of the pole) or/and for mounting
removable steps at regular intervals, allowing technicians to climb and stand in order to perform
tasks.
The production method of the poles of the invention has two production steps of the
aforementioned individual parts, and an assembly step. The first two steps, which are independent
of each other and can be executed in parallel, require specialized industrial equipment, personnel
and facilities. In contrast, the assembly step is designed so that it doesn't require specialized
personnel or facilities.
Specifically:
The constant cross section concave parts (tubes) of the poles of the invention can be produced by
various reinforced polymer production methods (resin transfer molding, contact molding, filament
winding, etc.), but are preferably produced by the pultrusion method, which is an industrial,
automated, large capacity and competitive method and gives products of reproducible quality and
dimensional accuracy.
The annular joints and the cap can also be produced by various reinforced polymer production
methods (casting, resin transfer molding, etc.), but are preferably produced by the compression
molding method, which also has the same - as abovementioned - characteristics, i.e. industrial,
automated, large capacity, competitive, reproducible and accurate in terms of the dimensions of the
produced products.
These individual parts of the poles (concave sections, joints and cap), which are produced as
abovementioned (by the pultrusion and compression molding methods respectively) are then
assembled dn a single pole, by using an adhesive and conventional (temporary or permanent)
mechanical restraint means (screws, pins, etc.).
The use of the poles of the invention as a modular product is feasible, because the step of the
poles assembly provided by their production method is not demanding in terms of expertise,
equipment, facilities, utilities, etc., and can therefore be performed by the end user of the poles,
with manuals and materials which are delivered together with the poles, even at the site of the final
installation of the poles.
Specifically:
The poles of the invention are delivered either fully assembled and ready for installation, i.e. as the
existing common poles are delivered, or as a modular product, i.e. divided in its individual parts.
In the second abovementioned case (modular product), the necessary tools, materials and
manuals of the on-site assembly are also supplied to the user, along with the parts of the poles to
be assembled.
Additionally, the design of the poles of the invention allows their packaging to be used as a modular
product in such a way so that the volume required during their transport is submultiple of the
volume of the assembled pole. This is done by placing the pieces of smaller cross section (with the
corresponding joints) in the pieces of the next larger cross section etc..
In this way the transport of the poles is facilitated and the corresponding cost is reduced,
particularly in cases where the poles must be installed in inaccessible locations and in cases where
the poles have to be transported over long distances (e.g. exports).
The poles of the invention are suitable for each and every use (power distribution,
telecommunications, lighting, etc.).
With the invention the existing cumulative advantages of the poles from FRP are enhanced and
expanded compared e.g. with wooden :
- availability, non-seasonal production
- excellent mechanical strength and elastic, predictable mechanical behavior
- long lifetime without requiring maintenance
- resistance against moisture, environmental attacks and the visible spectrum and UV radiation
- wide temperature operating range
- exemption from the need for impregnation with pesticides to protect against organisms
- repeatability of properties, dimensional stability and alignment
- ability to integrate inserted nuts and mounting parts of the pole equipment
- low weight, easy transportation and installation
- electrical insulation
- better behavior in car crushes, more safety and less damage to the vehicle and the network
- poles that do not sustain combustion (flame retardant)
- fine appearance (more aesthetics options)
- recycling
while the most important advantage of a competitive cost is also added compared to the alternative
options, since the poles of the invention have :
1. low production cost due to the industrial production methods used, and
2. even lower life cycle cost (total cost of use), which is the sum of the production cost plus the
costs of keeping a stock, transporting, handling, installation, inspection, maintenance, etc.) due
to their light and modular structure which allows easier transport, since the bulkier individual
parts can be placed one within the other requiring a much smaller space, and faster installation
with less means, especially when it must be done in inaccessible places.
These enable the successful industrial application of the invention.
The full development and detailed description of the characteristics and the operation of the
invention, the production method and the use as a modular product is made by designs (figures),
which show poles of the invention consisting of three cylindrical tube parts, with the corresponding
joints and cap.
However the use of poles of other cross sections is not excluded (e.g. polygonal, oval, with
functional recesses and channels, with stiffening ribs, etc.), representative designs (figures) of
which have also been added.
The selection of a smaller or a larger number of pole parts also is not excluded, depending on its
height, use and strength required.
The design of poles consisting of successive parts of constant cross-section of different shape (e.g.
cylindrical parts at the base for the even distribution of mechanical stresses and polygonal part(s)
at the top for the easier mounting of the arms and the support parts of the cables) also is not
excluded by appropriately adjusting the shape of the respective joints, in order to fit to the different
(upper and lower) sections.
Figure 1 shows (in perspective view and in side view) an example of a pole of the invention, which
consists of three successive cylindrical parts, which are connected with joints. The upper cylinder
has a cap.
In figure 2, the abovementioned pole is analyzed in its individual parts, which are illustrated in side
view and sectional view (B-B).
Figures 3, 4 and 5 show in greater detail (in perspective view, top view, side view and sectional
view) three individual parts of the pole with constant cylindrical section. The size of the cross
section of the lower part (5) is larger, of the middle part (4) intermediate and of the upper part (3)
smaller. All the parts with constant cross section may be produced by the pultrusion method.
Figures 6 and 7 show in greater detail (similarly) the joints that connect the successive cylindrical
sections in pairs. This means that the lower joint (6), which is larger one, connects the lower
cylindrical part of the pole with the intermediate, and the Upper joint (7), hich is smaller one,
connects the intermediate cylindrical part of the pole with the upper.
Each joint is designed so as to "receive" at appropriately shaped circumferential grooves
(recesses) the two cylindrical sections (upper and lower) which it connects, in order firstly to
achieve the strong adhesion between the joint and the sections with adhesive, and secondly the
assembling of the section to be performed accurately (the sections "end" in the grboves (recesses)
of the joint, without the need for measuring, leveling, etc.). All the joints can be produced by the
compression molding method. The design of the joints ensures that the successive sections
overlap at a small part of their length, so that the connection is resistant against bending.
Figure 8 shows in greater detail (similarly) the cap, which fits with the upper cylindrical part and is
placed on top of the pole of the invention. Regarding the connection of the cap to the cylindrical
part, the welding, its assembly and production (compression molding), exactly the same apply as
mentioned above for the joints. The design of the cap ensures tightness, regardless of good or bad
application of the adhesive. The top of the cap is slightly curved; however caps with flat, conical or
of any other shape surface are not excluded, depending on the requirements of the use.
Figure 9 shows (in perspective view and sectional view) a pole of the invention, which has two
transverse through holes at a short distance from its top for passing components, screws and
cables and at a lower height five transverse through holes (in vertical direction comparing to the
previous) for placing removable steps (stiles). Fitted, strong, inner tubes are welded at all the holes,
which : a. strengthen the pole and prevent its shattering in case threaded fittings, through-bolts,
etc., must be tightened, b. direct the passing of rods, cables, ropes etc., and c. prevent the
communication of the holes with the inside of the pole, the entry of water, insects, etc..
Figure 10 shows the assembly process of the pole of the invention in successive steps. All the
steps of the assembly can take place either at the factory (before the delivery of the pole as a
finished product) or on-site at the installation location (after the delivery of the pole as a modular
product).
At the first step of the assembly (A) the joints and the cap are welded to the corresponding lower
cylindrical sections, by applying an adhesive (K). The application of the adhesive can be made in
all possible ways (spreading, infusion, injection, etc.), depending on the viscosity of the adhesive
and the specific design of the joints and the sections. Similarly the type of adhesive application
equipment vary (spatula, pressing machine with static mixer, etc.). The welding can also be
combined with mechanical restrain, either permanent or temporary, until the completion of the
polymerization (hardening) of the adhesive.
The first step of the assembly (A) preferably takes place at the factory (before delivery) even when
the pole is delivered as a modular product. This is partly because, after the first step, the individual
parts of the pole may still be placed inside one another (in order to be transported easily and
inexpensively), and also because by performing the first step at the factory the labor that must be
done on-site and the corresponding installation time of the pole are reduced.
At the second step of the assembly (B) the joints are welded to the corresponding upper cylindrical
sections, by applying an adhesive (K). In this way the individual assemblies resulted from the first
step are joined to form the final pole (C). Regarding the application of the adhesive and mechanical
restraint exactly the same are applied as mentioned for the first step. When the pole is delivered as
a modular product, the second step is always performed on-site.
Figure 11 is a schematic representation of of adhesive application by injection in the gaps between
the joints and the cylindrical sections, by using the pressing device. In this case, the assembly
process consists o : a. the mounting Of the cylindrical parts at their place, which may be combined
with a permanent or temporary mechanical fixing (e.g. with pins), and b. the application of the
adhesive by the applicator through holes that lead the material to fill the gaps in order to achieve
the welding. If the adhesive has two components, the mixing occurs in a static mixer of the
applicator, to avoid mistakes.
Figures 12, 13 and 14 show the individual parts of another version of the pole of the invention of
octagonal cross-section. The pole of this version consists of successive sections of constant
octagonal cross-section, the corresponding joints that fit to the octagons and the cap similarly.
More specifically, Figure 12 shows (in perspective view, top view, side view and sectional view) a
part with an octagonal shaped constant cross-section, Figure 13 shows (similarly) an octagonal
shaped joint and Figure 14 shows (similarly) the corresponding cap.
Also Figure 15 shows the corresponding assembly steps of the octagonal pole which are not
substantially different from those of the corresponding cylindrical described above.
Figure 6 shows (in perspective view) a pole of the invention with an oval cross section. The joints
are designed to fit to the oval cross-sections, to ensure the required overlap and to connect
strongly. The image 16a shows two successive oval cross sections connected to a joint and image
16b shows an oval cross-section.
Figure 7 shows (in perspective view) a pole of the invention with a composite cross section, which
is cylindrical, but also forms an internal channel which facilitates the passing and protection of the
cables. Regarding the joints exactly the same are applied as mentioned above, with the addition
that also allow the contact/continuity of the internal channel throughout the height of the pole (see
image 17d). Also, image 17a shows two successive sections with a channel connected to the joint
and image 17c shows the same components (two cross sections and a joint) before the assembly.
Finally, image 1 b shows a cross section with a channel separately and image 17e shows a joint
separately.
Figure 18 shows (in perspective view) a pole of the invention with a composite cross section, which
is cylindrical, but also forms grooves for fixing channels, fittings, branch boxes, cables, etc..
Regarding the joints exactly the same are applied as mentioned above. Images 8a and 18e show
two successive sections with grooves, connected with a joint. Image 18b shows a cross-section
separately and images 18c and 18d show each joint separately.
Figure 19 shows (in perspective view) a pole of the invention which consists of successive sections
of constant cross-section of different shape. Specifically, the bottom section is cylindrical, while the
upper section is octagonal. Images 19a and 19b show two successive sections (cylindrical at the
bottom and octagonal at the top) connected to the joint, and image 19c shows the same
components (two cross sections and a joint) before the assembly. The joint (image 19d, separately)
that connects the two different sections, is designed so as to fit to both sections, having a circular
groove at its bottom side and an octagonal groove at its top.
All of the figures and images 20-21 and 22-26 describe all the steps of the assembly, packaging for
transportation and installation of a modular pole of three stages of the invention, from the
production of its individual pieces until the completion of its installation on-site. Figures 20-21 relate
to the steps that take place in the factory, while figures 22-26 relate to the steps that take place at
the installation location of the pole (on-site).
Figure 20 shows the individual parts of the pole, i.e. the cylindrical parts that have been produced
by the pultrusion method and the joints and the cap that have been produced by the compression
molding method, and the first assembly step of these pieces is described in pairs (see explanation
of figure 10 - step A, as mentioned above), which takes place at the factory. Images 20a and 20b
show the pieces (three sections, two joints and cap) separately from one another. Images 20c and
20d show the pieces glued in pairs (lower cylinder + lower joint, intermediate cylinder + upper joint,
upper cylinder + cap) as obtained after the step A of the assembly at the factory. Images 20e and
20f show the same abovementioned pairs but in reverse order (with no other change), that can be
placed one inside the other.
Figure 2 1 shows the placing of partially assembled pieces (pairs) telescopically one inside the
other. In this way the packaging is done in the factory before shipment, so as to reduce the length
and the volume occupied by the modular pole, to facilitate its transportation and to be possible
even by a smaller vehicle. Images 2 1a, 2 1c and 2 1e show (in side and perspective view) the pairs
as they are inserted into each other and images 2 1b, 2 1d and 21f (similarly) show the pairs
completely packaged in the smallest possible dimension.
Figure 22 shows (in side and perspective view) the first step of installation of the modular pole,
after its transportation on-site. The lower cylindrical section, which has the first joint already welded
at its top, is placed, leveled and anchored to the hole where the pole will be placed.
Figure 23 shows (in side and perspective view) the application of the adhesive (K) to the joint of the
first compacted part of the pole, which will be used for the welding of the next cylindrical section.
Figure 24 shows (in side and perspective view) the placing of the second cylindrical part of the pole
at the corresponding socket of the first joint, wherein the adhesive (K) has already been applied.
Because the compression molding and pultrusion production methods by which the joint and the
cylindrical part have been produced, respectively, are very precise regarding the dimensions and
the tolerances between the joint and the cylindrical part are very small, the placing of the second
part is simple, accurate and does not require new measurements and leveling.
Figure 25 shows (in side and perspective view) the application of the adhesive (K) at the joint of the
second, already placed, part of the pole, which will be used for the welding of the last, upper,
cylindrical part that also bears the cap.
In figure 26 (in side and perspective view) the installation of the pole is completed by placing the
third and last cylindrical part at the corresponding Socket of the second joint, wherein the adhesive
(K) has already been applied. Regarding the dimensional accuracy, the tolerances and the leveling
exactly the same are applied as abovementioned (for the figure 24).
If the adhesive is applied by injection by an applicator into appropriate for this purpose sockets
(holes) of the parts and the joints, then all the steps of the assembly/installation can be preceded
(figures 22, 24 and 26), the intermediate steps of the application of the adhesive are skipped
(Figures 23 and 25), and the application of the adhesive is done at the end of all the joints
(according to figure 11).
Figure 27 is a schematic representation of the production method of the poles of the invention as a
flow chart, which includes the production of the individual pole parts by the compression molding
(C) and pultrusion (P) methods, which can take place in parallel and independently from one
another, and then the assembly of the individual parts of the pole with adhesive (K) or/and
mechanical means, which may be done either at the factory or later by the user (in case the poles
are used as a modular product).
Example 1
In figure 28, an example of a pole of the invention ready to be produced industrially is shown with
all its dimensions.
The determination of the individual dimensions f the pieces that form the pole of the example was
made by using a finite element software package, taking into account firstly the mechanical
stresses and strains that the pole must resist and secondly the resistances of the reinforced
polymers from which the pieces are manufactured and the direction of these resistances
(compression molding isotropic material for the joints and the cap and pultrusion orthotropic
material for the cylindrical parts).
The pole of the example is 7m long and meets the requirements of the specifications relating to
poles of respective size suitable for installation in networks. It also meets the requirements of
relevant international standards (EN 50341 , EN 50423).
CLAIMS
Reinforced plastic (FRP) poles which consist of two or more successive concave parts (tubes)
of constant cross section, annular joints f the corresponding shape with circumferential
grooves at both their side's suitable for fitting the upper and the lower section that they
connect, and a cap of corresponding shape (similarly, with a circumferential groove at its lower
side) placed on top of the upper part (Figures 1 and 2).
2 . The poles of Claim 1, consisting of two or more successive cylindrical parts (Figures 3, 4
and 5), which are connected with annular joints (Figures 6 arid 7), and a cap (Figure 8) at
the top of the upper cylindrical part.
3. The poles of Claim 1, consisting of two or niore successive parts of constant polygonal
cross section (Figure 12), with the corresponding adjustment of the shape of the annular
joints (Figure 3) and the cap (Figure 14).
4 . The poles of Claim 1, consisting of two or more successive parts of constant oval cross
section (Figure 16), with a corresponding adjustment of the shape of the annular joints
and the cap.
5. The poles of Claim 1, consisting of two or more successive parts of constant cylindrical
cross-section (tubes), which includes an internal channel for passing the cables (Figure
17), with the corresponding adjustment of the shape of the annular joints and the cap.
6. The poles of Claim 1, consisting of two or more successive parts of constant cylindrical
cross section (tubes) which includes external grooves for fixing components, cables,
boxes etc. (Figure 18), with the corresponding adjustment of the shape of the annular
joints and the cap.
7. The poles of Claim 1, consisting of two or more successive parts of constant cross section
(tubes) of different shape (Figure 19), with the corresponding adjustment of the shape of
the annular joints and the cap.
8. The poles of Claim 1, with the addition of transverse through holes for passing of
components, screws and cables, the placing of removable steps (stiles) etc., at which
fitted, strong, inner tubes are welded (Figure 9).
9. The poles of Claim 1 with the addition of accessories (rings, inserted nuts and bolts, hooks
etc.) and configurations (channels, doors etc.) according to the user's needs.
The production method of reinforced plastic (FRP) poles by assembling individual parts, the
production of which is exclusively made by the pultrusion and compression molding methods
(versions SMC/BMC/Cold Press etc.) (Figure 27).
.The method of Claim 10, where the individual parts of the poles are firstly two or more
successive concave parts (tubes) of constant cross sections the production of which is
made by the pultrusion method, and secondly the annular joints and the cap the
production of which is made by the compression molding method (versions
SMC/BMC/Cold Press etc.) (Figure 27).
12 .The method of Claim 10, where the connection of the individual parts of the pole produced
by the pultrusion and compression molding methods is done by welding, by mechanical
means (screws, pins, etc.) permanently or temporarily until the hardening of the adhesive,
or by a combination of the above.
13.The method of Claim 10, here the application of the adhesive for the welding of the
individual parts of the pole produced by the pultrusion and compression molding methods
is made either before their assembly by spreading on their contact surfaces, or after the
assembly by injection by an applicator at a suitable for this purpose socket (Figure 11).
14. The use of reinforced plastic (FRP) poles as a modular product, which is delivered to the user
in the separate individual parts that constitute the poles before their assembly, along with the
necessary materials, tools and complete installation and assembly manuals on site (Figures
20-26).
15. The use of Claim 14, which is characterized by the fact that the poles are available in a
modular kit which includes two or more successive concave parts of constant cross section
(tubes), the respective joints, the cap, the connection accessories of the equipment, the
adhesive applicator, the components of mechanical restraint for assembly and the manuals
(Figures 0, 11 and 5).
1 . The use of Claim 14, which is characterized by the fact that the poles of the modular kit are
partially assembled so that the joints are already adhered to the previous (lower) part of
constant cross section, and the cap is already adhered to the top of the last upper part
(Figures 10-B, 15-B and 20c-20f).
17. The use of Claim 14, which is characterized by the fact that the poles of the modular kit are
packaged by placing one part into the other, telescopically, in order to require limited length
and space during storage and transportation, and the later to be possible by a smaller
transport mean (figure 2 1a-21f).