Note: Descriptions are shown in the official language in which they were submitted.
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System for Strengthening Poles
Background of the Invention
For wooden utility poles the most common mode of failure is the degradation of
the timber at ground level. For example, course grained wood in soft ground is
particularly susceptible to weakening over the course of time. Deterioration
is
promoted by the environmental conditions of the pole. Typically, the region
approximately 200 mm above and below the ground level decays, eventually to
the point where the pole is structurally unsound. The rest of the timber pole
typically suffers far less damage and can still be structurally sound when the
ground level is already significantly damaged.
The service life of deteriorated wooden poles can be extended by strengthening
the poles at ground level. By strengthening existing deteriorated poles, the
replacement of poles can be delayed. Extending the service life of poles as
opposed to simply replacing them is preferable as it is cheaper and minimises
interruptions to the utility supply.
One conventional solution to the problem of ground level deterioration of
wooden
utility poles is to wrap a support around the base of poles. This type of
solution
only provides little lateral support. Further, the wrap obstructs access to
the pole
for inspection, and also tends to create unfavourable local conditions that
encourage further deterioration. Another conventional solution to the problem
is
to fasten a supporting pin to the pole. A good connection can be achieved by
drilling and reaming a large hole through the pole, then bolting the pin to
the pole.
This solution however weakens the pole. Misalignment is also common in
existing
solutions, leading to poles not being sufficiently supported.
To counteract the adverse effects of ground level deterioration, a solution is
required that can safely reinforce damaged poles.
Another problem encountered when strengthening poles is that the pole supports
are exposed to tampering or theft. Therefore, a solution which improves the
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security of the pole strengthening system is required.
The present invention seeks to alleviate at least some of the above problems.
Statement of Invention
The present invention relates to a system for supporting a pole. According to
one
aspect of the present invention, the system comprises a support element for
supporting the pole; and fastening means for securing the support element to
the
pole; wherein the fastening means comprises a pair of mutually engaging
fastening parts, preferably including a bolt part and a corresponding nut part
adapted to engage with the bolt part; and wherein the support element
comprises
an aperture adapted to receive a first one of the pair of fastening parts, and
wherein at least one of the aperture and the first fastening part is shaped to
prevent rotation of the first fastening part when located in the aperture.
By preventing rotation of the first fastening part (which may be the bolt part
or the
nut part), installation can be simplified and subsequent tampering made more
difficult. Other types of fastening means and fastening parts may be used
instead
of a nut and bolt.
Preferably, the aperture is shaped to prevent rotation of the first fastening
part
when located in the aperture.
The first fastening part may comprise a shaped portion having a shape
corresponding to the shape of the aperture so as to prevent rotation of the
first
fastening part when the shaped portion is located in the aperture.
Preferably, the first fastening part is the bolt part.
The bolt part may comprise a head and a shaped portion shaped to prevent
rotation of the bolt part, the shaped portion being proximal or adjacent to
the
head.
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The bolt part may be arranged, when fully inserted through the aperture, so
that
the head abuts a surface of the support element around the aperture and the
shaped part of the bolt engages the aperture having a corresponding shape to
thereby prevent rotation of the bolt. Thus, when fully inserted the bolt will
preferably be held in place by the aperture.
The aperture and/or a portion of the first fastening part may have a non-
circular
shape, preferably a rectangular or square shape. Other non-circular shapes
(e.g.
hexagonal) could be used. Alternatively the shape could be substantially
circular
(or another shape) but with formations (e.g. complementary
notches/protrusions)
serving to prevent rotation (and thus lock the first fastening part into
place).
The second fastening part may be arranged for engagement with a fastening tool
to enable rotation of the second fastening part. The fastening tool is
preferably a
non-standard fastening tool as described in more detail below.
The second fastening part may comprise a head having one or more apertures
for engaging complementary formations on the fastening tool.
The system may further comprise one or more nails for insertion through the
one
or more apertures in the head of the second fastening part. This can allow the
nails to be driven into the pole to secure the second fastening part against
the
pole and thereby prevent subsequent rotation or slippage of the second
fastening
part.
The nails may be headless nails, also referred to herein as security nails.
This
can make tampering with the nails and the second fastening part more
difficult.
The second fastening part is preferably the nut part.
For added security, the nut part may be arranged to be recessed at least
partially,
optionally mostly or substantially fully, into the pole.
The support element may comprise at least one (preferably elongate) support
surface arranged to be placed against a surface of the pole to provide support
to
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the pole. The support surface is preferably curved, preferably with a
curvature
corresponding to that of the pole surface.
The aperture may be located in (extend through) the support surface.
The support element may comprise a plurality of apertures for use with a
plurality
of respective fastening means. This can improve the strength and durability of
the
system.
The system may comprise a plurality of support elements for fastening to the
pole.
According to another aspect of the present invention there is provided a
support
element for supporting a pole, preferably for use in a system as described
above,
the support element comprising: at least one (preferably curved) support
surface
adapted to be placed in contact with the surface of the pole to thereby
support the
pole; and at least one aperture adapted to receive a bolt for securing the
support
element to the pole, the aperture being shaped to prevent rotation of the bolt
when the bolt is inserted through the aperture.
The aperture may be shaped to allow the bolt to pass through the aperture and
to
engage a correspondingly shaped portion of the bolt such that rotation of the
bolt
is prevented.
The aperture may be non-circular, preferably rectangular or square.
The support element may further comprise a pair of apertures positioned so as
to
receive a pair of bolts which are angled relative to one another in a plane
perpendicular to the (radial) axis of the pole.
The apertures may be arranged to give an angle between the bolts, when
installed, of between 70 and 110 , preferably between 80 and 100 , more
preferably substantially 90 . This can improve the strength and rigidity of
the
system.
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The support element may have at least one ridge or rib lengthwise.
The support element may comprise two curved flanges arranged for placement
against the surface of the pole, the curved flanges separated by a ridge
extending
5 along the longitudinal length of the support element.
One or both of the flanges may be tapered to assist in insertion into the
ground.
According to another aspect of the present invention there is provided a bolt
for
use in securing a support element to a pole, preferably for use in the system
described above, the bolt comprising a head and a shaft, the shaft including a
shaped section, the shaped section shaped so as to prevent rotation of the
bolt
when the bolt is located in a correspondingly shaped aperture of the support
element. Preferably, the rest of the bolt shaft (the part of the bolt shaft
not
including the shaped section) has a circular cross section.
The bolt head may be arranged to substantially prevent manipulation by a
fastening/unfastening tool.
The bolt head preferably lacks formations suitable for engagement by a tool
and/or may have a flat or dome-shaped, preferably substantially smooth,
surface.
The shaft may have a length of between 95% and 98% of the pole diameter,
preferably substantially 97% of the pole diameter.
According to another aspect of the present invention there is provided a nut
for
use in securing a support element to a pole, preferably for use in the system
described above, wherein the nut has a head and a body with a threaded bore;
wherein the body is adapted to be recessed into the pole with the head
protruding
from the pole, and wherein the bore comprises a shoulder which is adapted to
guide a bolt into the bore. This can assist with alignment of nut and bolt and
so
simplify installation.
The shoulder may be one of: chamfered; or rounded.
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The nut head may have a form arranged to fit a non-standard tightening tool.
Use
of a non-standard tightening tool may improve security by preventing
tampering.
The term "non-standard tightening tool" preferably refers to a tool specially
adapted for use with the present system, for example by way of a tool part
designed for engagement with the nut head by way of a specially adapted shape
and/or specially adapted engagement formations corresponding to a shape
and/or engagement formations of the nut head.
The nut head may comprise formations adapted to engage with complementary
formations on a tightening tool, the formations comprising at least one of:
one or
more grooves; one or more recesses; one or more apertures; or one or more
protrusions.
The diameter of the nut body may be between 130% and 180% of the bore
diameter, preferably between 140% and 170%, more preferably between 150%
and 160%, or around 155%.
The diameter of the nut head may be between 180% and 380% of the bore
diameter, preferably between 220% and 340%, more preferably between 260%
and 300%, or around 280%.
The diameter of the nut head is preferably at least 120% of the nut body
diameter, or at least 130%, or at least 150%.
The nut head may have one or more apertures adapted to receive one or more
nails which can be inserted through the apertures into the pole.
One or more of the apertures for receiving nails may also be arranged to
engage
with corresponding formations on a tightening tool. This can simplify the
design of
the nut head.
According to another aspect of the present invention there is provided a
method
for reinforcing a pole, the method comprising: placing an elongate support
element adjacent to said pole; boring at least one bore hole through said
pole; for
each bore hole, boring a recess adapted to receive a respective nut; inserting
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through the support element and through each said at least one bore hole a
respective bolt; inserting in each at least one recess a respective nut; and
fastening each bolt to a respective nut. Recessing the nuts in this way can
prevent tampering. The nuts are preferably partially or mostly recessed,
preferably with only a nut head extending out of (and lying against a surface
of)
the pole as described elsewhere herein. The nut head is preferably
substantially
flat, and may for example be in the form of a disc, which may allow it to lie
flush
against the pole surface.
The two bore holes may be angled to one-another in the radial plane of the
pole
and adapted to receive a bolt each.
At least a portion of said bore hole and said recess may be bored in a single
step,
preferably using a single tool and/or a single drill bit.
In a further aspect of the invention, there is provided a boring or drilling
tool
having a drill bit, and/or a drill bit, preferably for use in or with a method
or system
as described above, comprising a first section (preferably a tip of the drill
bit,
preferably for drilling a bore through a pole to receive a bolt) and a second
section (preferably for drilling a recess for a nut) wherein the first section
has a
first diameter, preferably corresponding substantially to the diameter of the
bolt,
and the second section has a second diameter larger than the first diameter,
the
second diameter preferably corresponding to the diameter of the body of the
nut
(or other part of the nut which is to be recessed into the pole).
The first diameter may be between 12mm and 20mm, preferably between 14mm
and 18mm, for example around 16mm. The second diameter may be between
21mm and 29mm, preferably between 23mm and 27mm, for example around
25mm.
The second diameter may be between 130% and 180% of the first diameter,
preferably between 140% and 170%, more preferably between 150% and 160%,
or around 155%.
The depth of the recess preferably corresponds to the size of the nut which is
to
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be recessed, for example, between 48mm and 64mm, preferably between 52mm
and 60mm, or around 56mm. The depth may be between 300% and 400% of the
first diameter, preferably between 325% and 375% of the first diameter, for
example around 350% of the first diameter. The depth may be between 175%
and 275% of the second diameter, preferably between 200% and 250% of the
second diameter, for example around 225% of the second diameter.
The dimensions (e.g. diameters and lengths) of the sections of the drill bit
preferably correspond to the dimensions of the bolt/bore hole and nut/recess
as
described elsewhere herein.
The transition from first to second section may be gradual (e.g. sloped) or
may
comprise one or more step changes. The length of the first section may be
arranged to allow a complete bore hole to be drilled through the pole, for
example
at least 248mm, so that the total length of the drill bit is greater than the
diameter
of the pole (thereby allowing a nut recess and bore hole to be drilled in one
action), or may be shorter; in which case the drill bit may be arranged to
drill a
recess for a nut (using the second, wider section) and at the same time create
a
guide hole (using the first, narrower section) for subsequent boring of the
main
bore hole in a second step, using a different tool/drill bit. This can make it
easer
to ensure a good alignment between nut recess and main bore hole.
The tool / drill bit may be used in a method as set out above. In a further
aspect
of the invention, there is provided a method of preparing a pole (and/or
boring
one or more nut recesses and bore holes) using a drill bit as set out above.
The system and its elements set out above and described in more detail below
are preferably adapted for use with poles having a substantially circular
cross
section. However, the system may alternatively be used with poles having non-
circular (e.g. square) cross section. In that case, the support element need
not be
curved or have curved flanges as described. Instead the support element
(and/or
the described flanges) may instead be substantially flat, or may have any
other
suitable shape or configuration (e.g. U-shaped), preferably selected to enable
the
support element to be placed against, and provide support to, the surface of
the
pole.
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The invention extends to methods and/or apparatus substantially as herein
described with reference to the accompanying drawings.
Any apparatus feature as described herein may also be provided as a method
feature, and vice versa. As used herein, means plus function features may be
expressed alternatively in terms of their corresponding structure
Any feature in one aspect of the invention may be applied to other aspects of
the
invention, in any appropriate combination. In particular, method aspects may
be
applied to apparatus aspects, and vice versa. Furthermore, any, some and/or
all
features in one aspect can be applied to any, some and/or all features in any
other aspect, in any appropriate combination.
It should also be appreciated that particular combinations of the various
features
described and defined in any aspects of the invention can be implemented
and/or
supplied and/or used independently.
These and other aspects of the present invention will become apparent from the
following exemplary embodiments that are described with reference to the
following figures in which:
Figure 1 shows an overview of a pole strengthening system;
Figure 2 shows a cross section of a pole having been strengthened by the
pole strengthening system of Figure 1;
Figure 3 shows the preparation of the pole of Figure 1 for strengthening;
Figures 4 show schematic views of the support element used in the pole
strengthening system of Figure 1;
Figures 5 show schematic views of the nut and bolt used in the pole
strengthening system of Figure 1;
Figures 6 show schematic views of the nut, tightening tool, washer, and
security nails used in the pole strengthening system of Figure 1;
Figure 7 shows use of the tightening tool;
Figures 8 shows an example of a device adapted to install the pole
strengthening system of Figure 1; and
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Figure 9 shows an example process diagram of the installation of the pole
strengthening system of Figure 1.
Detailed Description of the Invention
5 Figure 1
shows a system for strengthening wooden poles 100 where a support
element 102 is securely fastened to a pole 100 using a system of bolts 104.
The
system may restore the pole to its former strength and enable the pole to
withstand loading even when there is a total decay of wood at or below ground
level.
The pole strengthening system (PSS) provides stability and extends the life of
a
pole without requiring any sound wood at ground level in order to be safe and
effective. The system may potentially support a pole for as long as 20 years,
or
longer. Further, the system has sufficient strength to restore a pole without
enclosing the deteriorated region. This advantageously permits natural
drainage,
and can also enable inspection, for example in order to monitor future pole
deterioration. At the same time, the present system is designed to discourage
or
prevent tampering.
The system described herein is adapted to strengthen a wide variety of poles
including substation poles, switch poles, small diameter poles, and other
poles
used in telephony networks, electrical networks, or other contexts. These
poles
may be wooden, or made from other materials. Replacing these poles can require
de-energising of the network, which not only requires considerably more safety
precautions, but can also lead to service outages. When repairing a pole using
the method described herein, generally the pole can be reinstated without the
need to have the conductors de-energised. The working height of the
reinstatement equipment ensures that work can be safely performed whilst still
maintaining the necessary safety distances from exposed conductors. This
allows
the overall costs associated with the reinstatement of poles to be minimised.
Although specific sizes and materials are described in relation to the
drawings, it
is clear that a range of different dimensions and materials are possible,
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corresponding to the situation in which the system is to be implemented.
Therefore, the user can select the most appropriate dimensions and materials
for
the particular application (for example, in the case of a standard telegraph
pole,
the dimensions and materials may be adapted based on the relevant pole
loadings). The dimensions given below and in the figures relate to an example
of
a wooden pole of standard size (for example a utility pole such as a wooden
telegraph pole) unless otherwise indicated.
It should also be noted that, though principally described in the context of
wooden
poles, the present approach may also be used with poles made from other
materials (for example metal street lamp poles may be reinforced using this
system with dimensions altered as necessary).
Figure 1 shows a pole 100 which is in need of strengthening. Poles 100
generally
extend into the ground, and rot 101 (in the case of wooden poles) or other
damage is common around ground level. The system might also be used, for
example, to deal with impact damage or a leaning pole. The pole strengthening
system described herein strengthens the section of the pole 100 around ground
level. The pole strengthening system comprises a support element 102 and at
least one bolt 104 with a corresponding nut 106. In one embodiment, the
support
element 102 is three metres long, formed from either 6mm or 8mm steel plate.
This size ensures adequate penetration into the ground and sufficient strength
to
provide support. The length of the support element 102 depends on the type of
ground it is driven into and the amount of loading it is expected to support.
Further details relating to the support element 102 are described below in
relation
to Figure 4.
In use, the support element 102 is driven into the ground adjacent to the pole
100
to a sufficient depth as to be able to support the loading from the pole
without
slippage. In one example, this is between 1.4 to 1.7m. The support element 102
is then attached to the pole 100 at a number of points by bolts 104 and nuts
106.
This solution can sufficiently strengthen poles, whilst permitting natural
drainage
and subsequent inspection. Installation is relatively straightforward and
economical.
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In the example of Figure 1, a single support element 102 is used. However,
more
than one support element may be used depending on loading and other
requirements. Multiple support elements 102 can be used, but there may be a
trade-off between stability provided and obstruction to natural drainage and
inspection. In one example where the pole 100 has approximately 30% decay at
ground level, adding a support element 102 as described herein restores the
pole
to 1.5 times its original strength (i.e. a supported, decayed pole can
withstand 1.5
times the load of a non-supported, non-decayed pole).
Figure 2 shows a cross-sectional view of the pole 100 of Figure 1 after being
strengthened. In this view, the cross-section through one bolt 104 is shown
for
clarity. Two or more bolts 104, at different pole cross-sections, different
orientations, or different lateral positions, can be used, for example four
bolts as
illustrated in Figure 1. The bolts 104 are placed through pre-bored holes in
the
pole 100 and are secured in place by nuts 106. The nuts 106 are sized so as to
recess into the pole 100 to a distance where the diameter of the bore hole
changes (see below and Figure 3). The nut 106 is sized so as to receive the
bolt
104 and has internal threading corresponding to the thread of the bolt 104.
The
bolt 104 is screwed in, preferably by rotating the nut 106 using tightening
tool 600
as described in more detail below. Advantageously, the bolts 102 are tightened
to
a torque of between 100 Nm and 150 Nm, preferably 130 Newton metres. This
torque ensures that the load is adequately transferred to the support element
102
without the bolt 104, nut 106 or support element 102 damaging the pole 100.
One
advantage of the recessed nut 106 construction is that the finished pole 100
has
no substantial protrusions.
Security nails 108 may be inserted through holes in the nut 106 and driven
into
the pole 100, thus securing the nut 106 and providing additional protection
against tampering. A locking washer such as a star washer may be placed
between the head of the bolt 104 and the pole 100 so as to prevent unscrewing
of
the bolt. The bolt head is shaped so that in cannot be gripped to be
unscrewed,
for example, by having a bevelled or smoothly rounded head. The bolt head is
preferably smooth without recesses or other formations for engagement with
screwdrivers, spanners, or other fastening tools, so as to prevent unfastening
once installed. A plain washer may be placed between the head of the nut 106
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and the pole 100 to distribute the pressure exerted by the nut 106 over a
wider
area of the pole 100.
Figure 3 shows the preparation of a pole 100 which is to be strengthened using
the above described apparatus and method. A through hole for the bolt 300 is
drilled with a drill 304. The bolt bore hole 300 has substantially the same
diameter
308 as the bolt 104 (in this example 16mm). Preferably, the bore hole 300 is
slightly larger than the bolt 104 to ensure that the bolt 104 can be inserted
easily.
The bore hole 300 extends through the pole 100, ideally (but not necessarily)
along the radial axis of the pole 100, passing through the centre of the pole
100.
The nut recess 302 at the opposing side of the pole 100 to that of the support
element 102 is bored at a larger diameter 310 than the bolt bore hole 300.
Advantageously, the nut recess 302 and bolt bore hole 300 are drilled at the
same time using a dedicated tool 304 which has tip 314 having a first diameter
corresponding to the diameter of the bore hole 300. This tip advantageously
has
a length the same as or longer than the length of the bore hole 300. The tool
304
then has a second section 316 with a diameter corresponding to the diameter of
the recess 302. This second section 316 advantageously has a length the same
as or longer than the depth of the recess 302. In an alternative embodiment,
the
bore hole 300 and the recess 302 are drilled separately.
In one example, the nut recess 302 has a diameter 310 of 25mm and a depth 306
of 56mm to receive the nut. These dimensions ensure, for a wooden pole, that
the bolt 104 can be tightened sufficiently and that the minimum amount of
material is bored out. Here also the diameter 310 and depth 306 may be
slightly
larger than the nut dimensions to ensure that the nut 106 fits properly. The
construction thus advantageously consists of a bore hole 300 extending along a
radial line through the centre of the pole 100. The bore has a step-change in
diameter at a depth 306 corresponding to the length of the nut 106. The
diameter
of the bore hole 300 increases from substantially the diameter 308 of the bolt
104
to the outer diameter 310 of the nut 106. It should be noted that for
different
poles, these dimensions may be different. In the case of a hollow metal pole,
there may be no recess 302, rather a hole bored through the shell of the pole
with
a diameter of the outer diameter of the nut 512, but smaller than the diameter
of
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the head of the nut 501 (Figure 5).
This construction affords the advantages of requiring a small amount of pole
material bored out, as the only recess is sized to fit the nut only, hence not
compromising the strength of the pole 100 unduly. There are also no exposed
nuts, which reduces the chance of damage or tampering. This also improves the
aesthetic properties of the pole 100 as a whole. The use of dedicated tool 304
also means that the nut 106 and bolt 104 automatically align and fit flush to
the
pole 100, as is described in more detail below.
Preferably, two bolts 104 (at slightly offset pole heights) are ideally
positioned so
that they are substantially orthogonal to each other. This ensures that the
bolts
104 provide substantial support whichever direction the load on the pole 100
is
orientated. In situations where orthogonal positioning of the bolts 104 is not
practicable, the bolts 104 are positioned as close to orthogonal as is
practicable.
This load is then transferred to the support element 102. To ensure that the
bolts
104 are substantially orthogonal, the support element 102 ideally covers an
angle
of at least 90 of the pole 100.
Figure 4 shows the support element 102 used in the pole strengthening system
described above and Figure 1. Figure 4 shows the profile of the support
element
102; it is substantially formed of two curved flanges 410, with a particular
radius
of curvature arranged to match that of the pole which the support element is
designed to fit around. Joining the two flanges 410, there is a rib 400 which
has a
rectangular cross-section. This is to improve the strength of the support
element
102. In the- above example, the radius of curvature of the flanges is 152mm
and
the rib is 80mm wide. The support element 102 is uniform in width all the way
along its length, in the above example; the support element is 194mm wide.
This
affords a simple manufacturing process as, for example, many pins 102 can be
stamped from a single sheet of metal with minimal wastage. The rib 400 tapers
from a radial extent of 110mm at the top to 17mm at the bottom as is
illustrated
by the side view of Figure 4(a). This aids insertion into the ground. In a
preferred
example, the rib 400 is manufactured separately and is welded to the pin 102
to
simplify the manufacturing process.
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In another example illustrated in Figure 4(d), the support element 102-1
tapers
402 towards the end which enters the ground to further aid the insertion into
the
ground. In one embodiment, the taper 402 only affects the size of the two
flanges
in a symmetrical fashion, and not the width of the rib 400. In this example,
the rib
5 extends
radially 60mm from the support element 102 and 80mm laterally at the
top of the support element 102. The rectangular rib 400 reduces in size also;
at
the base of the support element 102, the rib 400 extends radially 24mm from
the
support member, and has the same lateral dimension (as shown in Figure 4(d)).
This taper 402 does not affect the radius of curvature of the support element
102.
10 It is
designed so that the curved flanges of the support element 102 are in contact
with the pole 100 along the entire length of the support element 102.
Alternative
support element designs with more or fewer than one rib 406, different rib
cross-
section geometry 404 (e.g. as a curved or arched rib), and/or different
dimensions
may also be used.
As mentioned above, the support element 102 is attached to the pole 100 by the
use of an individually tailored nut part 106 and optionally washers on the far
side.
In this example the upper bolts are installed substantially 1.2m out of the
ground.
The support element 102 includes apertures 408 for receiving the bolts 104.
The
apertures 408 are preferably located as offset pairs. Specifically, the
apertures
104 of each pair are offset to one-another along the axis of the pole 100, so
that
respective bolts can pass through the centre of the pole 100 without
interfering
with each other. In the above example, this offset is 100mm, and the uppermost
pair of apertures 408 (on opposing flanges 410) are spaced 150mm and 250mm
from the top of the support element 102 respectively. Apertures 408 of each
pair
are positioned on opposite flanges 400, so that the bolts 104 are
substantially
orthogonal to one-another. Pairs of bolts 104 are ideally positioned with one
pair
being located near ground level and the other near the top of the support
element
102. In the above example, the pairs of apertures 408 on the same flange 408
are spaced 600mm from each other.
The apertures 408 are shaped so that they rotationally restrain a bolt 104.
This is
achieved by the apertures 408 being non-circular, for example square, and the
bolt 104 having a section 516 (see Figure 5) immediately next to the bolt head
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502 with a corresponding shape. This provides the advantage of the bolt 104
being held stationary when the nut 106 is screwed on, as will be described in
more detail below.
The bolt apertures 408 are shown to be square, but could be oval, hexagonal or
any other non-circular shape which the bolt 104 could fit in, hold the bolt
stationary and still bind the support element 102 to the pole 100.
Alternatively or preferably additionally, the non-circular shaped section of
the bolt
516 (see Figure 5) may engage with the material of the pole which rotationally
restrains the bolt 104. This may not be preferable in situations where the
pole 100
is degraded as the bolt 104 may slip and cause damage to the pole 100.
Figure 5 shows the bolt 104 and nut 106 used in the pole strengthening system
described above. The bolt 104 may for example be a coach bolt. In one
embodiment up to eight bolts are used for a pole reinstatement. Four is a
preferable number of bolts 104. Bolts 104 are preferably between 12mm and
20mm, more preferably between 14mm and 18mm, even more preferably,
approximately 16mm in diameter, heavy galvanised, with a length to suit the
pole
diameter. In the example above where the radius of curvature of the flanges of
the support element 102 is 152mm, the length of a bolt 104 is 295mm. This is
so
that the bolt 104 passes through the centre of the pole 100 and can engage
with
the recessed nut 106. The length of the bolt 104 is preferably between 90% and
99% of the pole diameter, more preferably between 95% and 98%, even more
preferably 97%.
The bolt 104 has a head 502, a shaft 518 and a non-circular section 516
between
the shaft 518 and the head 502. The non-circular section 516 is adapted to
engage with the non-circular apertures 408 of the support element 102. This
section 516 may be square, hexagonal or any other non-circular shape but
should match the shape of the apertures. The shaft 518 comprises threaded and
non-threaded sections.
The bolts 104 are inserted through the support element 102 and pole 100, and
when tightened with the nut 106, they clamp the support element 102 to the
pole
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100, effectively binding the pole 100 and ensuring the integrity of the
reinforced
pole.
Unlike systems where both the nut and bolt can be rotated relative to each
other
by way of suitable tools (for example an operator may hold the bolt stationary
by
means of a tool during tightening whilst turning the nut with another tool or
vice
versa), in the present system only the nut can be rotated using an appropriate
tool. This makes the system less susceptible to tampering. The bolt 104 as
described above is held rotationally stationary by shaped apertures 408 (this
also
conveniently means that only one tool is required to tighten or loosen the
nut). To
further improve security, the bolt head can be shaped to prevent gripping
and/or
rotation by a tool. As an example, the bolt head may have a flat or dome-
shaped,
substantially smooth surface.
Furthermore, since the nut is recessed into the pole it is less accessible
(e.g. to
spanners, pliers or similar standard tools) and can preferably only be
manipulated
using a specially adapted tool, as described in more detail below.
The non-circular holes 408 in the support element 102, combined with the
correspondingly shaped section 516 of the bolt 104 stop the bolt 104 rotating
during tightening. Furthermore, the use of a lock washer 500 placed in between
the bolt head 502 and the support element 102 further ensures that the bolt
104
does not slip when tightening.
The nut 106 fits into the hole drilled and reamed into the exterior surface of
the
wooden pole 100. The size and shape of the nut 106 ensures that the support
element 102 remains in contact with the pole 100 at all times, even if
shrinkage of
the timber occurs. The nut has a head 501 at one end and a bore 504 that is
threaded 506 at the other end. The threaded end 506 of the nut is recessed
into
the pole 100. For example a typical length of the recessed part 508 of the nut
106
is between 35mm and 80mm, preferably between 50mm and 60mm, more
preferably approximately 56mm (for a pole diameter of approximately 300mm).
The threaded part of the nut 506, at the inner surface of the bore, can be for
example 35mm long. It can also extend until the end of the bore 504 at the nut
head 501. The threaded part of the nut 506 must be long enough to prevent the
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bolt 104 from tearing out at a sufficient degree of tightening. The bolt 104
can be
cut to length so that it does not protrude from the nut head 501. The
cylindrical
wall 510 of the recessed part of the nut 508 should preferably be thick enough
to
provide sufficient strength, while not be so thick as to weaken the wooden
pole
100 from excessive reaming for the nut recess 302. For example, an outer
diameter 512 of the recessed part 508 of 25mm for a M16 bolt is suitable. In
general, an outer diameter 512 of the recessed part 508 of about 130% to 180%
of the bolt diameter 514 is suitable, or preferably approximately 155%. These
features provide the ability to tighten the nut 106 to the bolt 104 with a
torque of
130Nm.
In a preferred embodiment the nut 106 has a wide enough head 501 to distribute
the load so that nut 106 does not sink in (even without the use of additional
washers). The wide head 501 also protects the hole 302 from dampness. In one
embodiment, the nut head 501 is 70mm in diameter and 3.5mm thick, but
different sized heads 501 may be used. For example a particularly weak pole
100
may require a large nut head 501 to ensure that the nut head 501 does not sink
into the pole 100. Unlike the recessed part of the nut 508, the head 501 sits
against the surface of the pole.
In a preferred embodiment, at the threaded end 506 of the nut the shoulder 514
is
shaped to assist insertion of the bolt 104 so that the bolt 104 self-centres
to the
centre of the nut 106. In the example illustrated here, the shoulder 514 is
chamfered to guide the bolt 104 into the thread 506. Alternatively, the
shoulder
514 can be rounded, tapered or angled. When the bolt 104 engages with the nut
106, the shoulder 514 centres the bolt to the lumen of the nut.
The nut can for example be fabricated from steel, and is preferably galvanised
to
European Standards (EN) after forming.
Figures 6 and 7 shows the nut 106 and tightening tool 600, and security nails
108
and washer 700 used in the pole strengthening system (PSS) described above.
The nut head 501 is formed into an individual shape that fits a tightening
tool 600
with a complementary shape. In the example illustrated here, the nut head
shape
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501 comprises two through holes 602 arranged in specific locations on the head
501. The tightening tool 600 has a complimentary shape with two studs 604
arranged in locations corresponding to the holes 602 in the nut head 501.
Different configurations may of course be used. For example, three holes may
be
used, or the holes may be eccentrically placed. Other types of complementary
surface formations on the nut head and tightening tool may also be used to
allow
engagement between tool and nut.
Generally, a huge variety of modifications to the nut head 501 can be made to
individualise the nut 106. This gives the advantage that different operators
can be
supplied with individual nuts and corresponding tools so that only that
operator
can remove the pole support element 102. By using non-standard, individualised
nut and tool designs in this manner, the risk of tampering can be reduced
because the nut cannot easily be removed with standard tools. Furthermore, as
discussed above, the bolt head is also shaped so that it cannot easily be
gripped
with standard tools.
To improve security of the construction further, as well as to provide
additional
advantages, security nails 108 can be used. Security nails 108 may be
hammered into the pole 100 through holes in the nut 106 so that they are flush
with the nut 106 (as illustrated in Figure 2). In a preferred embodiment, the
nails
108 have no heads; they simply fill the holes in the nut 106 so that the nut
106
cannot be removed without tampering with the nails. The nails 108 may be
inserted into the tightening holes 602 of the nut 106 until flush with the
holes.
Here, the nails 108 prevent tampering with the nut 106, as the tightening tool
600
can no longer be fitted into nut 106. Alternatively the nails 108 may be
inserted
into separate, dedicated holes in the nuts 106. The nails 108 are optionally
threaded so that when they are tapped in, they screw themselves into the
wooden pole 100. The nails 108 also prevent the nut 106 from rotating and
hence
loosening.
The nails 108 provide a further advantage in that one can easily tell if the
tension
of the bolt 102 has changed by the position of the nail 108. At a later
inspection, if
the nail 108 is not flush with the nut 106, but is sunk in or appears skewed,
the
nut 106 may have loosened (for example due to warping of the pole) and needs
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re-tightening. When the support element 102 is to be dismounted from the pole
100, the security nails 108 can be hammered further into the pole 100 so that
the
rotation of the nut 106 is no longer obstructed. Further, the same holes in
the nut
106 can be accessed by the tightening tool 600 to loosen the nut 106. The
5 support element 102, bolts 104, and nuts 106 can then be re-used.
In some instances, a large plain washer 700, for example 100mm outer diameter,
may be placed between the head 501 of the nut 106 and the pole 100. This
washer 700 can help distribute the pressure exerted by the nut 106 over a
wider
10 area of the pole 100, and can therefore enable additional tightening of
the nut
106 and bolt 104, resulting in better connection of the pole 100 to the
support
element 102. In one example, the large washer 700 is formed from 4.0mm plate
and is galvanised to European Standard (EN) after forming. However in
embodiments using the security nails, the nut head 501 preferably has a large
15 enough diameter so that use of a washer 700 is not necessary, as the
washer
might otherwise obstruct insertion of security nails 108.
The features described above can make the pole strengthening system a safe,
cost effective, practical and secure method of restoring a decayed pole to
20 serviceable condition.
PSS Installation Process
Figure 8 shows one example of a device adapted to install the Pole
Strengthening System as described above. The device is adapted to be fitted
onto a mechanical excavator, tractor or other piece of machinery.
The installation device 800 attaches to a support member 102 by slotting a
securing bolt (not illustrated) through holes 804. Holes 804 are positioned
either
side of the ridge 400, which has a corresponding hole 808 through it. The
installation device 800 comprises a head part 806 which rests on the top of
support member 102 which provides support when driving the support member
102 into the ground.
Installation device 800 comprises a hydraulic breaker 802 which moves
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reciprocally up and down, acting to push the support member 102 into the
ground. This process is continued until the support member 102 is at the
correct
depth. The installation device 800 engages with the top of the support member
102 and extends down a point on the support member 102 above where the
flanges 410 start to taper. When the support member 102 has been driven into
the ground to a sufficient depth, the installation device 800 can be
disconnected
by removing the securing bolt. Ideally, this is a quick-release bolt. In one
embodiment, this comprises a bolt with a handle attached so that it can be
inserted and removed quickly.
Figure 9 shows an example process diagram of the installation of the pole
strengthening system.
S1 Mounting: the support element 102 is driven down the side of the pole 100
into the ground using a pile drive method. This is ideally achieved using
vibration
driving using the installation device described above. The support element may
for example be pushed into the ground at an angle, to ensure that the base of
the
support element pushes into the pole. Poles that have completely failed at
ground
level can be held in place. The ridge 400 in the support element 102
strengthens
the support element 102, aiding both the insertion process and the strength of
the
support element 102 post-installation. The support element 102 does not
require
fixation to the pole 100 with concrete, for example. The support element 102
is
then attached to the pole 100 using a system of bolts 104 and nuts 106 as
described above.
S2 Drilling: as illustrated in Figure 3, holes 300 of the appropriate diameter
308
for the bolts 104 are drilled through the pole 100 at the appropriate
positions for
attachment of the support element 102. At the hole outlet opposite the support
element a recess 302 is drilled to accommodate the nut 106. For this purpose,
a
special drill bit 304 is used which has a narrower tip 314 of the same
diameter
308 as the drill bit 304 for the bolt through hole 300; and is enlarged 316 at
a
distance from the tip to the same diameter 310 as the nut recess 302. For
example, the tip 314 of the bit 304 may be 16mm diameter (for an M16 bolt),
and
further away from the tip the bit is enlarged 316 to a diameter of 25mm. This
change is preferably a step-change, but may be a sloping change, or a series
of
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small step changes. The tip 314 of the drill bit may not extend all the way
through
the pole 100, rather it just creates a guide hole for subsequent drilling with
improved alignment.
The stepped drill bit 304 enables alignment of the recess 302 for the nut 106
with
the bore hole 300 of the bolt 104. Thanks to this alignment the nut head 501
is
flush with the pole 100, and the risk of the nut 106 and bolt 104 being
misaligned
is reduced. This can be beneficial in enabling sufficient tightening of the
nut 106
to the bolt 106. The drill bit 304 may optionally have another shoulder (not
illustrated) at some distance along the enlarged section 316 of the bit 304 to
ensure that the nut recess 302 is of the correct depth 306. In the example
discussed so far, this would be at 56mm along the enlarged section 316 of the
bit
304. The drilling and mounting stages may alternatively be performed in the
opposite order.
S3 Bolting: The nut 106 is inserted in the recess 302 opposite the support
element 102, if necessary by knocking it in. From the support element side of
the
pole the bolt 104 is then inserted. The nut 106 guides the bolt 104 into the
threaded section 506 by means of the chamfered or rounded shoulder 514. The
bolt 104 is usefully pre-cut to the correct length so that it does not
protrude out of
the nut 106. Bolts 104 are inserted at cross-angles above ground, ideally at
right-
angles to one another, or as close to right angles as practical. The distance
between pairs of bolts 104 is ideally as large as possible to reduce moment
loads
on the bolts 104. The bolts 104 are preferably heavily greased prior to
fitting, to
reduce the impact of water damage occurring.
S4 Tightening: The nut 106 is tightened to approximately 130Nm using a
tightening tool. The bolt 104 is held rotationally in place by the non-
circular
section 516 engaging with holes 408 in the support element 102 as described
above. Referring to Figures 6 and 7, the tightening tool 600 has a design
corresponding to the design of the nut head 501. Ideally, it is of a non-
standard
design to minimise the chance of tampering. In one example, this design
consists
of two protrusions 604 spaced from the centre of rotation of the tool. These
protrusions 604 then couple with correspondingly placed holes 602 in the nut
106. Alternatively, as described above, each operator or client can have their
own
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nut tool with corresponding nut shape for tightening.
S5 Securing: Security nails 108 can then be tapped through holes in the nut
106
to provide the advantages discussed above.
After installation as set out above, checks can be carried out as required to
ensure the integrity of the installation. Finally, the pole strengthening
system can
be dismounted when no longer needed (e.g. when the pole 100 is taken out of
service). These steps are summarised below:
S6 Inspection: In this step, the pole is checked to see if the support element
102
is pulled in tightly against the pole 100. This can be by checking to see if
security
nails 108 are still intact and in the correct placement.
S7 Dismounting: The bolts 104 can be removed by unscrewing the nuts 106 with
the specially adapted tightening tool 600 (after removing or tapping in the
security
nails 108 if used). The support elements 102 can then be extracted. Support
elements 102, bolts 104, and nuts 106 can be reused. This reusability can
provide environmental benefits.
Criteria for Assessment to determine suitability for strengthening
In some cases, a pole 100 may be strengthened using the described system
even if it is unserviceable for normal duties. There may even be little or no
sound
wood present at or below ground line. In an embodiment of the pole
strengthening system, requirements might include:
= Internal Rot: Preferably at least 60 mm of sound wood measured at 1
metre above ground line (a Matson borer can be used to ascertain the
amount of sound wood available).
= External Rot: External rot of treated sapwood should preferably not
penetrate more than 20 mm, provided there is at least 70 mm of sound
wood (probing the surface of the pole with a screwdriver, for example,
provides information as to the extent of any external rot).
The above requirements are given purely as examples of requirements that might
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apply in a particular context or embodiment. Other embodiments and other
application contexts may have different requirements, which may be more or
less
stringent.
It will be understood that the present invention has been described above
purely
by way of example, and modifications of detail can be made within the scope of
the invention.
For example, although the pole strengthening system has been described for
reinforcing poles at ground level, any portion of a pole may be reinforced
using
the system, in which case the support element may be of a different shape
(e.g.
instead of being tapered, the support element may have substantially the same
width along its length, and additional bolts may be used).
Each feature disclosed in the description, and (where appropriate) the claims
and
drawings may be provided independently or in any appropriate combination.
Reference numerals appearing in the claims are by way of illustration only and
shall have no limiting effect on the scope of the claims.
