Note: Descriptions are shown in the official language in which they were submitted.
CA 02599029 2007-08-27
"TIE-DOWN BRACKET"
FIELD OF THE INVENTION
[00011 The present invention relates to a bracket for use as a connector
between a
flexible tie-down strap and an anchor screw pile, applied, for example, in the
context
of a pipeline tie-down assembly.
BACKGROUND OF THE INVENTION
[0002] Despite being buried beneath the ground, pipelines, such as those used
to
convey oil or gas, sometimes undergo longitudinal and/or upward movement. Such
movement can arise from elongation or contraction due to temperature changes,
both
inside and outside the pipeline. It also can arise due to buoyancy effects
when
traversing water-saturated soil, such as muskeg.
[0003] It is common practice to tie down or restrain upward movement of the
pipeline, to counteract the movement. This is usually accomplished using what
is
referred to as a pipeline tie-down assembly or system.
[0004] There are two main categories of pipeline tie-down systems. One uses
weights to hold the pipeline down. The other uses anchors, usually screw
piles,
embedded in the ground and bracketing the pipeline, with the anchors connected
by a
restraining cross-piece extending over and across the pipeline.
[0005] The present invention relates to an anchor-type system which can be
used to
restrain buried pipelines, gas station storage tanks and the like.
[0006] One particular example of an anchor-type pipeline tie-down assembly is
disclosed in Canadian patent 2,191,145, issued to Johannesson et al. This
assembly
comprises:
a pair of embedded screw piles for bracketing the pipeline;
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CA 02599029 2007-08-27
= a flexible tie-down strap having loop ends;
= a pair of brackets, each mounted on the upper end of a screw pile, the
bracket
comprising a tube, which slides over the pile end and which can rotate or
pivot
theron, and a coaxial sleeve which is connected to the tube at one side
thereof;
= whereby one of each of the strap loop ends threads through one of the
sleeves
to connect the strap at its ends with the brackets;
= first means are provided on the upper end of each screw pile, for limiting
the
downward travel of the bracket at a pre-determined elevation; and
= second means are provided on each pile for disengagably locking the bracket
against upward movement when it is seated on the first means.
[0007] There are problems associated with a bracket such as that disclosed in
the
aforementioned prior art.
[0008] More specifically:
= The ends of the strap are doubled back and sewn to the central portion of
the
strap, to create the loops. Sewing is normally carried out at a facility `in
town'. As a consequence, the strap ends are threaded through the sleeves and
sewn at this facility. The strap and brackets are therefore necessarily
conveyed to `the field' as a unitary assembly;
= As a result, if the strap needs to be replaced, it can't be easily separated
in the
field from the brackets. Furthermore, one end of the strap, attached to its
heavy steel bracket, usually needs to be passed across the exposed pipeline in
the course of the assembly. There is a risk that the bracket may be
inadvertently dropped on the pipeline and may damage the impermeable
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plastic coating on the steel pipe of the pipeline. This is highly undesirable
from the point of view of the pipeline contractor;
= In addition, it is sometimes desirable to introduce a second pipeline beside
the
first and this may require replacing the strap with a longer one. And finally
the pipeline owner will usually maintain an inventory of tie-down parts. It is
desirable in that connection to have separate components.
[0009] For these reasons there is a need for a modified bracket that can
easily be
engaged and disengaged with the strap in the field.
SUMMARY OF THE INVENTION
[0010] In accordance with the invention a bracket is provided which can easily
be
connected or disconnected in the field with the loop end of a flexible tie-
down strap.
[0011 ] The bracket comprises:
= a tube for sliding over the upper end of an embedded screw pile, whereby the
tube is pivotally mounted on the pile; and
= a cleat, connected to the tube and positioned at one side thereof, said
cleat
having a pair of horns protruding horizontally and transversely from the tube
when the latter is upright, as it would be when positioned on the screw pile.
[0012] The bracket may incorporate one or more of the following preferred
features:
= each horn comprises a thicker inner root portion and a thinner outer
terminal
portion;
= the terminal portion of each horn is angled or bent inwardly toward the
tube;
= the cleat is positioned intermediate the ends of the tube; and
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CA 02599029 2007-08-27
= the horns are configured to conform with the engaged strap loop end so that
the side portions of the loop can seat and bear against the thick root portion
of
the cleat.
[0013] In a tie-down assembly embodiment of the invention, a pair of the
brackets are
pivotally mounted on the upper ends of a pair of embedded screw piles
bracketing a
member to be restrained, such as a pipeline. A flexible tie-down strap having
loop
ends extends across the member. The loop ends releasably engage the brackets.
Removable stop means limit the upward travel of the brackets along the screw
piles,
at pre-determined elevations.
[0014] This embodiment may incorporate one or more of the following preferred
features:
= the strap loop ends are each formed with a folded twist; and
= each loop end extends over the tube and is trapped beneath the cleat of its
associated bracket and bears against the surface of the bottom end of the
tube,
to thereby engage the cleat and lock against the tube.
DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 is a top view of a bracket in accordance with the invention ;
[0016] Figure 2 is a front side view of the bracket;
[0017] Figure 3 is a side view of the bracket;
[0018] Figure 4 is similar to Figure 1, with the addition of showing a strap
loop end,
having a folded twist configuration, engaging the cleat of the bracket;
[0019] Figure 5 is similar to Figure 2 with the addition of showing the strap
loop end
releasably engaging the bracket;
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[0020] Figure 6 is similar to Figure 3 with the addition of showing the strap
loop end
engaging the bracket with the end portion of the loop trapped beneath the
cleat and
bearing against the surface of the bottom end of the tube;
[0021 ] Figure 7 is a side end view showing a pipeline in a ditch with
embedded screw
piles bracketing the pipeline, the pipeline being restrained with a tie-down
assembly;
[0022] Figure 8 is a side view showing the upper end of a screw pile with a
bracket
mounted thereon and engaging a strap loop end and a lock nut limiting upward
movement of the bracket; and
[0023] Figure 9 is a front side view of the bracket mounted on the upper end
of the
screw pile and locked in place by a lock nut.
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DESCRIPTION OF A PREFERRED EMBODIMENT
[0024] Having reference to the Figures, a bracket 1, for use in the context of
a
pipeline tie-down assembly 7, is shown. The bracket I comprises a tube 2
having a
cleat 3 connected thereto. The bracket 1 functions as a connector between a
loop end
4 of a flexible tie-down strap 5 and an embedded screw pile 6.
[0025] As shown in Figure 7, the pipeline tie-down assembly 7 comprises a pair
of
embedded screw piles 6 bracketing a pipeline 8 and joined by the tie-down
strap 5.
The screw piles 6 function as anchors and the tie-down strap 5 functions to
restrain
the pipeline 8 against upward movement.
[0026] In greater detail, each screw pile 6 comprises a shaft 9 having one or
more
helices 10 attached to its lower end. The shaft 9 is usually comprised of
connectable
sections so that the length of the shaft may be varied to allow the helices 10
to be
embedded in a solid ground formation. The upper end 11 of the shaft 9
protrudes
above the bottom surface 12 of a ditch 13 at the time of constructing the tie-
down
assembly 7. As shown in Figure 8, a removable tubular stop 19 overlies the
shaft 9
and may be disengagably locked in place by nut and bolt 19a. The stop 19
carries a
shoulder 14 at its lower end, for limiting the upward movement of the bracket
1 at a
pre-determined elevation.
[0027] The bracket tube 2 is sized to slide over and fit the shaft's upper end
11. It is
free to rotate or pivot thereon.
[0028] The cleat 3 is connected to the tube 2 and is positioned at one side
thereof. It
comprises a pair of horns 15 which protrude generally horizontally and
transversely
from the tube 2, when the latter is positioned over the screw pile 6.
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[0029] Each horn 15 is somewhat arcuately shaped. It comprises an inner root
portion 16 and an outer terminal portion 17. As shown, the root portion 16 is
thicker
than the terminal portion 17. The terminal portion 17 is angled or bent
inwardly
toward the tube 2. Each root portion 16 provides a surface 18 against which
the loop
end 4 may bear when the loop end 4 and cleat 3 are engaged. The thicker root
portion
16 is intended to resist the pull of the strap 5. The thinner terminal
portions 17
function to contain the loop end 4 and resist having it slip off the cleat 3.
[0030] The cleat 3 is connected to the tube 2 at a point intermediate its
ends. As a
result, the lower end of the tube 2 forms an underlying surface 20 against
which the
central portion 21 of the loop end 4 may bear when the strap 5 engages the
bracket 1.
[0031 ] The strap loop ends 4 are each formed with what is known as a folded
twist
22.
[0032] In assembly, each loop end 4 is extended over its associated bracket
tube 2 and
is then doubled back so that its central portion 21 seats against the tube
underlying
surface 20 and is trapped beneath the cleat 3. The side members 22 of the loop
end 4
seat against the seating surfaces 18 of the horn root portions 16 as the loop
end 4 is
drawn tight.
[0033] From the foregoing it will be appreciated that the loop ends 4 of the
strap 4
can be readily engaged or disengaged in the field with brackets 1 mounted on
the piles
6.
[0034] The cleat horns 15 are shown in this preferred embodiment as generally
arcuate so that, even though short and compact in length, they still function
to retain
the engaged loop ends 4 in place. However it is contemplated that they could
be
straight, although longer, or could be provided with protruberances or other
means to
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assist in retaining the loop end in place. While a stop shoulder 14 has been
shown as
the means for limiting upward travel of the bracket 1 on the shaft upper end
11, other
means, such as threaded engagement between the shaft 9 and bracket 1, could
also be
used. Other variants for the various components of the assembly will be
apparent to
one of ordinary skill in the art.
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