U.S. patent application number 11/200717 was filed with the patent office on 2005-12-08 for composite poles with an integral mandrel and methods for making the same.
Invention is credited to Boynoff, Michael, Cherkas, Paul.
Application Number | 20050271845 11/200717 |
Document ID | / |
Family ID | 33417142 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050271845 |
Kind Code |
A1 |
Boynoff, Michael ; et
al. |
December 8, 2005 |
Composite poles with an integral mandrel and methods for making the
same
Abstract
The invention is a composite pole with an integral mandrel
therein and methods of making the same. A preferred embodiment is a
fiberglass reinforced resin composite pole such as a utility pole
or a lighting pole. The integral mandrel is preferably an expanded
plastic foam such as expanded polystyrene. The integral mandrel is
contoured to be in the desired inside configuration of the
composite pole and fiber reinforced composite naterial is applied
to the mandrel. The pole is used with the mandrel remaining
therein, thus strengthening the pole. Passages may be placed into
the mandrel for routing conduits and pipes as desired
Inventors: |
Boynoff, Michael;
(Mendocino, CA) ; Cherkas, Paul; (San Jose,
CA) |
Correspondence
Address: |
Foothill Law Group, LLP
Suite 130
3333 Bowers Ave.
Santa Clara
CA
95054
US
|
Family ID: |
33417142 |
Appl. No.: |
11/200717 |
Filed: |
August 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11200717 |
Aug 11, 2005 |
|
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10436359 |
May 12, 2003 |
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Current U.S.
Class: |
428/36.9 ;
428/36.1 |
Current CPC
Class: |
B29C 44/1285 20130101;
Y10T 428/1362 20150115; Y10T 428/1372 20150115; B29L 2031/766
20130101; Y10T 428/1376 20150115; E04H 12/02 20130101; Y10T 428/139
20150115; B29C 70/086 20130101; Y10T 428/1393 20150115; B32B 37/00
20130101; B29C 70/32 20130101 |
Class at
Publication: |
428/036.9 ;
428/036.1 |
International
Class: |
B32B 001/08 |
Claims
What is claimed is:
1. A composite pole comprising an outer shell of a composite
material and an integral mandrel therein, wherein the outer shell
is formed about the integral mandrel, wherein the integral mandrel
defines at least one longitudinal passage.
2. The composite pole of claim I wherein the composite material
comprises a matrix component and a reinforcing component.
3. The composite pole of claim 2 wherein the reinforcing component
comprises a material chosen from the group consisting of
fiberglass, aramid fibers, and carbon fibers.
4. The composite pole of claim 2 wherein the matrix component
comprises a resinous material chosen from the group consisting of
material chosen from the group consisting of epoxies, polyesters,
acrylics, phenolic resins, and urea-formaldehyde resins.
5. The composite pole of claim 1 wherein the integral mandrel
comprises an expanded or extruded insulating foam.
6. The composite pole of claim 5 wherein the expanded or extruded
insulating foam comprises polystyrene foam.
7. The composite pole of claim 1 wherein the integral mandrel
comprises a material chosen from the group consisting of expanded
polystyrene, extruded polystyrene, and rigid polyisocyanate.
8. The composite pole of claim 1 wherein the integral mandrel
comprises a plurality of longitudinal sections.
9. The composite pole of claim 1 wherein the horizontal cross
section of the integral mandrel is chosen from the group consisting
of circles, ellipses, and polygons.
10. The composite pole of claim 1 wherein the vertical cross
section of the integral mandrel is tapered.
11. The composite pole of claim 1 wherein the vertical cross
section of the integral mandrel is a right cylinder.
12. The composite pole of claim 1 wherein the moment of inertia of
the composite pole is greater than the moment of inertia of a
hollow pole comprising said outer shell.
13. The composite pole of claim 2 wherein the integral mandrel
comprises a protective coating for protecting said mandrel from
attack by the matrix component.
14. The composite pole of claim 1 wherein the pole is made by a
filament-winding process, a pultrusion process or a pullwinding
process.
15. The composite pole of claim 1 with an antenna wire routed
through the at least one longitudinal passage.
16. The composite pole of claim 1 with a power wire routed through
the at least one longitudinal passage.
17. The composite pole of claim 1 wherein the at least one
longitudinal passage comprises a plurality of longitudinal passages
and wherein the plurality of longitudinal passages contain a
plurality of conduits, one conduit to a passage, where there are at
least two conduits chosen from the group consisting of electrical
wires, communication wires, and fluid flows.
18. A composite pole comprising an outer shell of a composite
material and at least one integral mandrel therein, wherein the
outer shell is formed about the at least one integral mandrel,
wherein the at least one integral mandrel defines at least one
longitudinal passage.
19. The composite pole of claim 18 wherein the integral mandrel
comprises a plurality of longitudinal sections, wherein the at
least one longitudinal passage is in alignment relationship among
the plurality of longitudinal sections.
20. The composite pole of claim 18 wherein the at least one
integral mandrel comprises expanded polystyrene foam.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention pertains to composite poles, such as utility
poles, light poles and antennas having an integral foam core and
methods of making and using them.
[0003] 2. Description of the Prior Art
[0004] There is a substantial prior art with respect to composite
poles such as utility power transmission poles, light poles, and
the like, and methods of making them. Composite poles refers to the
fact that the poles are formed from a combination of different
materials each of which maintains their identities in the
combination to produce a superior result than could be achieved
from the individual materials. The composite for making poles is
generally fiber-reinforced plastic (FRP), typically fiberglass
fibers in a resin matrix, producing what is generally called a
fiberglass pole. The reinforcing fibers are not limited to
fiberglass, however, and can include the likes of asbestos, jute,
sisal, aramid fibers, carbon fibers, and synthetic fibers, though
fiberglass has typically been associated with large poles. Resin
refers to any polymer that is the matrix for a composite, such as
epoxies, polyesters, acrylics and other polymers. The major
requirement is that the reinforcing material forms a strong bond to
the resin.
[0005] The process for making fiberglass poles involves forming a
hollow tube while the resin is in a plastic state and then curing
the resin. Curing refers to the process of converting the resin
from a plastic state to a hardened state by application of heat,
catalyst, ultra-violet light or reactants (curing agents) which
convert the resin into a hardened structure, generally three
dimensional cross linked structure, which is insoluble and will
decompose before it melts.
[0006] There are two principal classes of processes known in the
prior art for making composite, principally fiberglass poles. These
are known as filament winding and pultrusion. A third alternative
is a hybrid of filament winding and pultrusion.
[0007] Filament winding refers to a process for making an FRP in
which a continuous filament or tape is treated with resin and wound
onto a mandrel (a metal form whose outer shape is the same size as
the desired inner surface of a pole under construction) in a
predetermined pattern. The process is performed by drawing the
filament from a spool or creel (a creel is a spool and supporting
structure) through a bath of resin, then winding it onto the
mandrel under controlled tension and in a predetermined pattern.
The mandrel may be stationary, in which case the creel structure
rotates above the mandrel, or it may be rotated on a lathe about
one or more axes. After a sufficient number of layers have been
wound the resin is cured and the hardened hollow pole is removed
from the mandrel.
[0008] U.S. Pat. No. 4,089,727 to Hardy-The McLain, which is hereby
incorporated herein in its entirety by reference, disclosed an
apparatus and method for preparing a member by wrapping a mandrel
with discrete layers of fiber by applying filaments in expanded
helices while selectively varying the lead angle of helically
disposed fibers along the length of the member. This is
accomplished with a unique apparatus that controls the relative
axial and rotational movement between a winding head, which
dispensed the filament, and the mandrel. This invention is
particularly useful in applying filament to a tapered mandrel to
make a tapered pole.
[0009] Since one of the major problems with composite poles is the
cost, it is particularly desirable to minimize the amount of
fiberglass component. It is common to make tapered poles with a
base having a larger diameter than the tip. When a tapered pole is
made by applying windings from base to tip to provide layers of
fiber reinforced resin on a tapered mandrel, the resulting pole
tends to have a thicker wall at the basis. This is the opposite of
what would be desired based on the strength requirement for a pole
and results in loss of some of the economies of tapered poles U.S.
Pat. No. 5,492,579 to Hosford, which is hereby incorporated herein
in its entirety by reference, disclosed a computer modeled pole in
which the layers do not extend the entire length of the pole, thus
allowing a pole with longitudinal zones, having thicker walls at
the base, thin walls at the tip and intermediate wall thickness
between the base and the tip, and approximate minimum weight for a
pole of a given strength. Filament winding is a preferred method of
making circular cross section poles.
[0010] The second class of processes for making composite poles is
pultrusion. Pultrusion refers to a continuous process for
manufacturing composites with a constant cross-sectional shape. The
process consists of pulling a fiber reinforcing material through a
resin impregnation bath and into a shaping die where the resin is
subsequently cured. The fiber reinforcing Heating to both gel and
cure the resin is sometimes accomplished entirely within the die
length, which can be on the order of 76 cm (30 inches) long. In
other variations of the process, preheating of the resin-wet
reinforcement is accomplished by dielectric energy prior to entry
into the die, or heating may be continued in an oven after
emergence from the die. U.S. Pat. No. 4,803,819, to Kelsey, which
is hereby incorporated herein by reference, discloses use of
pultrusion to make hollow composite utility poles having
diametrical reinforcing struts which add strength to the hollow
pole. Pultrusion may pull strands, rovings (a collection of
parallel strands which are not twisted together), spun roving (a
collection of teisted or braided strands), or mats (randomly
oriented chopped filaments or swirled filaments with a binder cut
to the contour of a mold). Pultrusion may produce a tube which is
unsupported and merely sawed into lengths after hardening.
Alternatively the form may be shaped around a mandrel. Pultrusion
is a preferred way of making non-circular cross section poles.
[0011] Pulwell Industries (Zhongshan Pulwell Composites Co; Ltd)
has a variation known as pullwinding which combines the pultrusion
and filament winding methods, by pulling a longitudinal composite
layer onto a mandrel followed by applying helically wound layers by
filament winding. This approach supplies a tube with high crush
strength as well as the stiffness of pultruded poles
[0012] It is known in the prior art, that the use of a core
material sandwiched between composite layers can reduce the cost
and add strength to a laminated structure. In U.S. Pat. No.
4,682,747 to King, an insulted cross arm for supporting wires on a
utility pole is disclosed, comprising an outer shell of polyester
resin and a inner core of polyurethane form. Also in U.S. Pat. No.
5,513,477 to Farber discloses a composite, tapered poles made in
segments which are assembled to make a hollow, tapered pole when
assembled. In one of Farber's preferred embodiments the segments
are made of an outer skin and an inner skin of fiber reinforced
resin with a foam block "core" bonded between them in the annual
space between the outer skin and the inner skis The word "core" in
this context refers to the central layer of a laminate to which the
outer layers of the laminate are attached.
[0013] While composite poles have many valuable uses, there is a
need for improvement in several areas.
[0014] There is a need for less expensive composite poles. There is
a need for less expensive composite poles by reducing the wall
thickness of the poles. There is a need for improved and simplified
methods of construction of composite poles.
[0015] There is a need for composite poles with greater strength
that is not simply accomplished by thicker walls.
[0016] Composite poles made by existing processes of filament
winding and pultrusion are by their very nature hollow poles
(allowing for internal struts as described above in Farber). The
original use was as a substitute for wooden utility distribution
poles. In this application, the function of the original wooden
pole can be mimicked without routing conduit or other vessels
through the pole. However, in other applications the interior of
the pole is very important For example, light poles, power poles
(e.g. poles for connecting to underground wires), and antennas, all
have internal wires which could be provided for in the pole. Also,
other mixed use poles could be used to route power lines, data
lines, optical lines, and process lines such as lube oil or
coolant. There is a need for composite poles having internal
provision for routing wires, conduit, process lines and the
like.
SUMMARY OF THE INVENTION
[0017] One preferred embodiment of the invention is a process for
making a composite pole including the steps of shaping an integral
mandrel into the form desired for the pole's interior and then
applying a plurality of layers of reinforced composite material to
the integral mandrel to form a pole including the composite
material and the integral mandrel. The reinforced composite
material includes a matrix component and a reinforcing component.
The matrix components are resinous materials such as epoxies,
polyesters, acrylics, phenolics, or urea-formaldehyde resins that
cure to form a bond with the reinforcing material. The reinforcing
component is a fibrous material such as fiberglass, aramid fibers,
carbon fibers, or any of the other fibers that can be used for
making fiber-reinforced plastics. In some cases a very desirable
pole can be made from a combination of fibers, such as combination
of fiberglass and aramid or carbon fibers. In general, the
requirement is that the choice of matrix and reinforcing components
be such that the matrix forms a strong bond with the reinforcing
component.
[0018] The integral mandrel is preferably fabricated from an
expanded insulating foam, preferably expanded polystyrene foam.
Alternative preferred mandrel materials include extruded
polystyrene and rigid polyisocyanate. Depending on the type of foam
or plastic and the type of composite, the foam or plastic may be
coated or otherwise treated to impart protection from the composite
while the composite is being applied to the at least one integral
mandrel prior to the matrix reaching a cured condition. The
integral mandrel is said to be integral because it is not separated
from the composite to form a hollow tube as in the prior art poles,
but it serves as a mandrel during fabrication and remains an
integral part of the finished pole. Since an integral mandrel
becomes part of the finished pole, its utility is much greater than
merely being a form for the inside surface of the composite as in
prior art mandrels. In particular an integral mandrel can
advantageously be provided with longitudinal passages or chases
through which wires, conduits, or pipes can be conveniently placed
while being thermally and electrically isolated by the insulating
foam. Expanded foams such as polystyrene can be precisely contoured
by hot wire shaping in lengths of up to ten or fifteen feet and
diameters up to at east three feet. For longer poles the integral
mandrel is made in longitudinal sections shaped to align with each
other. The sections are then butted end to end to form the integral
mandrel. In most cases, the integral mandrel will have a central
passage that can be placed onto a rod to assemble the sections and
to hold the integral mandrel while the composite is being
applied.
[0019] Any of the prior art methods for applying a composite to a
mandrel, such as filament winding, pultrusion and pullwinding can
be used with an integral mandrel. The conditions for operation must
be consistent with the properties of the properties of the integral
mandrel material. For example in the case of expanded polystyrene,
the maximum use temperature is about 160.degree. F. and the choice
of matrix and/or pretreatment of the integral mandrel must be
compatible with applying and curing the composite below this
temperature. Pretreatment of the integral mandrel can include such
steps as applying an external polyethylene envelope, sealing a
polystyrene integral mandrel with plastic cement or applying a
sealer such as a Portland cement--polymer mixture of the type that
is often used to seal polystyrene foam in construction
applications. Another optional approach is to use composite layers
having different matrix components. For instance applying a first
layer which is compatible with and protective of the mandrel and
subsequent layers which have other desired properties.
[0020] Another aspect of the invention is a composite pole
comprising an integral mandrel therein. A preferred embodiment of a
composite pole comprises a fiberglass containing composite and a
polystyrene integral mandrel having at least one chase through the
interior of the integral mandrel. Poles can be any shape commonly
used for poles, such as right cylinders of circular or polygonal
horizontal cross section, or tapered cylinders.
[0021] Another aspect is a method for routing a plurality of
components through a pole comprising the steps of fabricating at
least one integral mandrel having a passage for each of the
plurality of components, applying a plurality of layers of
reinforced composite material to the at last one integral mandrel,
and routing the plurality of components through the plurality of
passages.
[0022] The use of an integral mandrel in making a pole simplifies
the pole manufacture because it is not necessary to extract the
reinforced composite tube from the mandrel. Also, for a given pole
strength, less wall thickness is required, and fewer layers of
reinforced composite need to be applied.
[0023] The integral mandrel strengthens the pole, thus reducing the
wall thickness of the composite required to achieve a particular
strength.
[0024] The integral mandrel can be adapted to provide insulated
passages for wires, conduits and process pipes through the
pole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] These and other features, aspects ard advantages of the
present invention will become better understood with regard to the
following description, appended claims and accompanying drawings,
where:
[0026] FIG. 1 shows a top view of a circular cylindrical pole.
[0027] FIG. 2 shows a top view of a square cross section pole.
[0028] FIG. 3 shows a top view of an octagonal cross section
pole.
[0029] FIG. 4 is a vertical cutaway view of a pole in a first
configuration where the pole is supported by an above ground
collar.
[0030] FIG. 5 is a vertical cutaway view of a pole in a second
configuration where the pole extends into the ground for
support.
[0031] FIG. 6 is a front view of a tapered pole.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The invention pertains to improved composite poles and
methods for making them. Composite poles are well known in the art
and are frequently used to support electrical and/or telephonic
distribution wires (distribution poles) and light poles. Composite
distribution poles have advantages over wooden poles because they
can be much lighter than their wooden counterparts and do not need
to be treated with dangerous preservatives. As previously
discussed, prior art composite poles have been hollow poles, often
formed on a steel mandrel having the desired shape of the interior
surface of the hollow pole. The hollow pole is extracted from the
mandrel after the composite cures. The instant invention relies on
forming the composite around an integral mandrel that will stay
with the pole and provide useful benefits not previously known in
the prior art.
[0033] It should be understood that as applied herein the following
terminology will be used as defined below in a manner not
inconsistent with the way the terms are used in the art.
[0034] A composite material refers to a multiphase material formed
from a combination of materials which differ in composition or
form, remain bonded together, and retain their identities and
properties.
[0035] A fiber-reinforced composite (FRC) refers to a composite
structural material containing high-strength fibrous material
embedded in a resinous matrix which when the resin cures develop
mechanical properties greatly superior than the base resin. In the
current context the fiber is often fiberglass, hence the incorrect
usage that FRC refers too fiberglass reinforced composite.
[0036] A resin refers to any polymer that is used as a matrix in
composites to contain the reinforcement material.
[0037] Curing refers to the change in the properties of a plastic
or resin by chemical reaction, for example by condensation,
polymerization, or addition. Curing may occur in the presence of
elevated temperature, pressure, or catalysts.
[0038] Curing agents refers to substances or mixtures of substances
added to a polymer composition to promote or control the curing
reaction. An agent which does not enter into the reaction is known
as a catalytic hardener or catalyst. A reactive curing agent or
hardener is generally used in much greater amounts than a catalyst,
and actually enters into the reaction. Crosslinking agents are
distinguished from catalysts because they react with molecules and
are coupled directly into the cured system as a structural member
of the polymer.
[0039] Fiber refers to a single homogeneous strand of material
having a length of at least 5 mm, which can be spun into a yarn or
roving, or made into a fabric.
[0040] Filament refers to a long continuous fiber used in making a
FRC pole.
[0041] A mat is a fibrous material for reinforced plastic
consisting of randomly oriented chopped filaments or swirled
filaments with a binder cut to the contour of a mold. Mats are
available in blankets of various widths, lengths and weights.
[0042] A strand is a bundle of filaments in a single compact unit
without a twist.
[0043] A roving is a number of strands collected into a parallel
bundle.
[0044] A spool is a cylindrical piece about which a filament is
wound.
[0045] A creel is a spool and its supporting structure on which
continuous strands or rovings of reinforcing material are
wound.
[0046] A mandrel is a form around which pultruded or filament wound
poles are shaped.
[0047] An integral mandrel is a form around which a composite pole
is shaped and which remains an integral part of the finished
pole.
[0048] Tape refers to a unidirectional fiber or filament
impregnated with resin.
[0049] The filament winding process is one of the principal
processes for making a composite pole. It refers to an automated
process in which continuous filament (or tape) is treated with
resin and wound on a mandrel in a helical pattern. Reinforcements
commonly used are single stands or rovings of glass, asbestos,
carbon, aramid, jute, sisal, cotton and synthetic fibers, while the
resins include epoxies, polyesters, acrylics, phenolics,
urea-formaldehydes and others. To be effective, the reinforcing
material must form a strong adhesive bond with the resin. The
process is performed by drawing the reinforcement from a spool or
creel through a bath of resin, then winding it on the mandrel under
controlled tension and in a predetermined pattern. The mandrel may
be stationary, in which event the creel structure rotates above the
mandrel, or it may be rotated on a lathe about one or more axes. By
varying the relative amounts of resin and reinforcement, and the
pattern of winding, the strength of filament wound structures may
be controlled to resist stresses in specific directions. After
sufficient layers have been wound, the structure is cured. Filament
winding is discussed in U.S. Pat. Nos. 4,089,727 and 5,492,579.
[0050] Pultrusion is a second principal process for making
composite poles. It refers to a continuous process for
manufacturing composites with a constant cross-sectional shape. The
process consists of pulling a fiber reinforcing material through a
resin impregnation bath and into a shaping die where the resin is
subsequently cured. In most cases, the composite is gelled and
cured by heating within the die, which can be on the order of 76 cm
(30 inches) long. In other variations of the process, curing
continues beyond the die while the pole is formed around a mandrel.
The pultrusion process yields continuous lengths of material with
high unidirectional strengths. Pultrusion is discussed in U.S. Pat.
No. 4,803,819.
[0051] Pullwinding is a hybrid of pultrusion and filament winding
processes. In pullwinding filaments are pulled onto mandrel while
other filaments are wound onto the mandrel in a helical pattern.
This combination produces a pole with high strength both axially
and radially.
[0052] One aspect of the invention is a process for making a
composite pole comprising shaping an integral mandrel to a desired
internal configuration and then applying layers of composite
material to the integral mandrel.
[0053] The process can be advantageously applied to producing
so-called fiberglass poles, though it is not limited to fiberglass
and may be applied to other fibers such as but not limited to
aramid or carbon fibers. A preferred material for an integral
mandrel is an expanded insulating foam, more preferably expanded
polystyrene foam. Alternative mandrel materials com extruded
polystyrene and rigid polyisocyanate. Expanded polystyrene can be
precisely contoured using hot wire shaping, technology which is in
wide use today and is well known to those skilled in the art.
Pieces can be readily handled in the range of diameters up to about
three feet and lengths up to about 10 to 15 feet. Longer poles can
be made by using an integral mandrel in separate longitudinal
sections of 10 to 15 feet butted together.
[0054] An integral mandrel is shaped on its outer surface to
conform to the shape desired for the composite portion of the pole
that will be formed around it. The integral mandrel is also,
preferably, shaped on the interior to provide longitudinal
passages. In most applications, the integral mandrel has at least
one longitudinal passage in the center that will be used to hold it
on a rod when the composite is applied.
[0055] Other longitudinal passages are formed into integral mandrel
to conform to the use intended for the pole. Insulating foam has
many desirable properties as a material for an integral mandrel,
such as thermal and electrical insulating properties. Polystyrene
foams are also available with high antistatic properties such as
expanded polystyrene made from DYLITE.TM. X44-SF antistatic
expandable polystyrene (ARCO Chemical). Antistatic foam would be
advantageously applied to routing DC power lines through a pole
between a wind turbine and an inverter to prevent line losses.
[0056] Expanded polystyrene is also available in forms that provide
magnetic shielding. This form of integral mandrel would be
desirable for isolating data transmission lines.
[0057] The insulating and isolating properties of a foam integral
mandrel allow mixed use poles having a plurality of passages filled
with various conduits routing electrical wires, signal lines, fiber
optic lines, and process flows such as grease, oil, or coolant. The
many applications and uses will be apparent to those skilled in the
art.
[0058] The presence of an integral mandrel in the finished pole
also provides additional strength compared to a conventional hollow
pole, therefore the requisite thickness of the composite, i.e. the
number of layers of reinforced composite put on the mandrel, is
reduced due to the presence of the integral mandrel in the pole.
This effect is illustrated in Example 1, with respect to the
increase in moment of inertia of a hollow pole and a pole with an
integral mandrel. It important to note that the maximum improvement
in moment of inertia is achieved with poles made according to the
instant invention, because the moments of the components (the
hollow tube and the integral mandrel) are additive. Moments of
bodies are additive only when they are bound together so that they
react as a single unit.
[0059] Layers of composite material are applied to the integral
mandrel by the same types of processes that are used for forming
conventional hollow poles on conventional mandrels. One preferred
method is filament winding where filaments treated with resin are
wound about the mandrel as filaments, strands, rovings, or tapes to
form layers. Many ways of winding are possible within the scope of
the invention, preferred methods and patterns include those
described in U.S. Pat. Nos. 4,089,727 and 5,492,579, where the
later applies particularly to tapered poles.
[0060] It is important to note that the choice of composite
materials and operating conditions particularly for curing the
resin must be compatible with the properties of the integral
mandrel. For a polystyrene foam integral mandrel the mandrel should
not be heated above about 140 to 160.degree. C., also polystyrene
will dissolve in many organic solvents. The temperature limitation
favors epoxy resins and urea formaldehyde resins that cure at low
temperature. Curing agents and catalysts are preferred to heat for
curing the resinous matrix.
[0061] A preferred option is to treat the formed foam prior to
applying the composite. Preferred treatments include applying a
film coating, such as a polyethylene coating prior to applying the
composite. Another treatment is to apply a protective coating such
as are commonly used to protect polystyrene foam in construction
applications, such as a polymer--Portland cement mixture. Another
alternative is to dip the foam mandrel in plastic cement.
[0062] The conduits and pipes may be inserted in the longitudinal
passages either before or after application of the composite. They
are preferably inserted prior to application of the composite.
[0063] Pultrusion can also be used to apply the composite to the
integral mandrel. In this case filaments, strands, or rovings
impregnated with resin are pulled axially on to the integral
mandrel with or without a forming die. Pultrusion can also be used
by pulling a mat onto the mandrel. The same considerations apply
here as with filament winding with respect to operating conditions
and materials. In this application of pultrusion, it is preferred
not to cure the resinous matrix by heating the extrusion die, but
rather to cure on the mandrel due to chemical and/or catalytic
reaction.
[0064] Pullwinding can be applied to an integral mandrel by pulling
axial layers and winding helical layers.
[0065] The process can be applied well to tapered poles, right
cylindrical poles, poles with circular or elliptical, or polygonal
horizontal cross section. A long pole is made by using a mandrel
having a plurality of sections. The passages are aligned from
section to section. The sections are threaded onto a rod through a
central longitudinal passage and held together at the ends so that
the sections butt end to end.
EXAMPLE 1
[0066] This example shows how the strength of a pole with an
integral mandrel is stronger than a hollow pole for a given wall
thickness, or in the alternative a pole need have less wall
thickness for a given strength.
[0067] The moment of inertia is a term used to describe the ability
of a cross section to resist bending.
[0068] For a hollow cylinder the moment of inertia, I, is given by
equation (1).
I=(1/2)(M)(b.sup.2+a.sup.2) (1)
[0069] Where: I is the moment of inertia, M is the mass of the
hollow cylinder, b is the outside radius of the cylinder, and a is
the inside radius of the cylinder.
[0070] The moment of inertia of a solid cylinder is given by
equation (2).
I=(1/2)(M)(a).sup.2 (2)
[0071] Were a is the radius of the cylinder.
[0072] For a hollow pole with an integral mandrel the overall
moment is the sum of the two parts.
[0073] The density of the fiberglass composite is 120 pounds per
cubic foot, and the density of the expanded fiberglass foam is 3
pounds per cubic foot. The comparison below shows the moment of
inertia for a hollow pole and for a pole with integral mandrel for
a 40-foot high pole with 36-inch diameter, and 0.3-inch wall
thickness.
[0074] I (hollow pole)=2482 pound-foot squared
[0075] I (pole and integral mandrel)=3373 pound-foot squared
[0076] Put another way, a wall thickness for the tube and mandrel
of only 0.19 inches has a moment equal to the 0.30-inch hollow
pole.
[0077] Another preferred embodiment is a composite pole having an
integral mandrel therein. The composite pole comprises an outer
composite portion made up of a resinous matrix and reinforcing
fibers. Preferred matrix materials include epoxies, polyesters,
acrylics, phenolics, and urea-formaldehydes. Preferred reinforcing
fibers include fiberglass, aramid fibers and carbon fibers. The
integral mandrel is preferably an expanded insulating foam, more
preferably expanded polystyrene foam. The integral mandrel
preferably contains longitudinal passages, which may be filled with
various wires, conduits, and pipes. The pipe cross section can be
circular, elliptical, or polygonal. The pole may be either tapered
or right cylindrical.
[0078] Turning to the figures, FIG. 1 shows a circular cross
section pole 100 with an integral mandrel 102, a composite outer
wall 104, and longitudinal passages (chases) 106, 107, and 108
which may carry fluids, electrical wires, optical fiber lines,
radio signal carriers, and the like.
[0079] FIG. 2 shows similarly a square cross section pole 110, with
an integral mandrel 112, a composite outer wall 114, and
longitudinal passages (chases) 116, 117, and 118 which may carry
fluids, electrical wires, optical fiber lines, radio signal
carriers, and the like.
[0080] FIG. 3 shows an octagonal cross section pole 120, with an
integral mandrel 122, a composite outer wall 124, and longitudinal
passages (chases) 126, 127, and 128 which may carry fluids,
electrical wires, optical fiber lines, radio signal carriers, and
the like.
[0081] FIG. 4 is a vertical cutaway, of a pole 130 supported by an
above ground collar 131. The cutaway view shows the outer composite
wall 134, and three conduits 136, 137, and 138 filling vertical
passages in the integral mandrel 132. The conduits exit at the
bottom of the pole below ground level 133.
[0082] FIG. 5 shows a similar pole 140 supported by a portion of
the pole concreted below ground level 143 from the concreted
section 141. The cutaway view shows the outer composite wall 144,
and three conduits 146, 147, and 148 filling vertical passages in
the integral mandrel 142
[0083] FIG. 6 shows a tapered pole 160, with a composite wall 164,
an integral mandrel consisting of two parts 162, and 163 and a
single conduit 166.
[0084] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions are possible. Therefore the spirit and
scope of the appended claims should not be limited to the preferred
versions herein.
* * * * *