Note: Descriptions are shown in the official language in which they were submitted.
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A COLLAR FOR A CONCRETE LIFTING ANCHOR
Field of the Invention
This invention relates to a collar for a concrete panel lifting anchor and,
more
particularly but not exclusively, to a concrete panel lifting anchor formed of
bent wire
having a collar to provide clutch abutment surfaces.
Background of the Invention
It is known to lift a concrete panel by way of an anchor embedded within the
concrete panel during casting of same. A typical anchor of this kind is formed
from metal
by cutting the anchor from a plate, and is cut so as to provide clutch
abutment shoulders to
limit rotation of a lifting clutch relative to the anchor. However, the
applicant has
identified that such typical anchors are relatively expensive to produce due
to the cutting
procedure, and that use of such typical anchors may be restrictive as the
anchor must be
located at or near a central plane of the panel. Lifting anchors fabricated by
cutting plate
material require a lot of energy to produce, and often have irregularities.
Disadvantages
also result from the anchors being cut from plate, as the anchors are
typically planar and
for correct orientation for lifting require legs of the anchor to extend
across a large portion
of the thickness of the concrete panel. Moreover, the applicant has identified
that a
significant amount of waste material is produced as a by-product in the
manufacture of
existing lifting anchors.
Examples of the invention seek to solve, or at least ameliorate, one or more
disadvantages of previous lifting anchors.
Summary of the Invention
In accordance with one aspect of the present invention, there is provided a
collar
for an anchor for use in lifting a concrete component, said anchor comprising
a head
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portion engagable with a clutch of a lifting system, and a body portion for
embedment with
the concrete component, the collar including an attachment portion for
attaching the collar
to the head portion of the anchor, and an abutment portion adapted to provide
a clutch
abutment surface for limiting rotation of the clutch relative to the anchor.
Preferably, when the collar is fitted to the lifting anchor the abutment
portion forms
the clutch abutment surface as a shoulder adjacent the lifting anchor. More
preferably, the
clutch abutment surface is formed as a shoulder adjacent the head portion for
limiting
rotation of the clutch about an eye of the head portion. More preferably
still, the abutment
portion provides a shoulder adjacent each side of the head portion for
limiting rotation of
the clutch about the eye in both directions of rotation. The collar may
include a gap
between the shoulders which coincides with the eye of the head portion to
allow passage of
the clutch through the eye.
Preferably, the abutment portion is formed by an edge of the collar.
In a preferred form, the collar fits around the head portion, and is held to
the head
portion by way of a press fit.
Preferably, the collar is generally C-shaped.
In a preferred form, the collar includes at least one shear bar attached to
the collar.
More preferably, the shear bar engages in a groove of the collar. Preferably,
the shear bar
is welded to the collar. In one example, the shear bar is formed in a
generally wave-like
shape, with oscillations in a direction generally perpendicular to a central
axis of the
anchor when the collar is fitted to the anchor. More preferably, the collar
includes a
second shear bar, wherein a major axis of the second shear bar is generally
parallel to a
major axis of the first shear bar and is substantially a mirror image of the
first shear bar
when viewed from an end of the anchor.
In accordance with another aspect of the present invention, there is provided
an
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anchor for use in lifting a concrete component, said anchor comprising a
single length of
wire bent to form a head portion engagable with a clutch of a lifting system,
and a body
portion for embedment with the concrete component, wherein the anchor has a
collar to
provide clutch abutment surfaces for limiting rotation of the clutch relative
to the anchor,
the collar being a collar as described above.
Brief Description of the Drawings
The invention is described, by way of non-limiting example only, with
reference to
the accompanying drawings in which:
Figure 1 is a perspective view of a lifting anchor having a collar in
accordance with
an example of the present invention;
Figure 2 is a perspective view of the anchor of Figure 1, shown with an
associated
chair;
Figure 3 is a perspective view of the anchor, shown with the chair fitted
thereto;
Figure 4 is a side view of the anchor, with the chair fitted thereto;
Figure 5 is a top view of the anchor, with the chair fitted thereto;
Figure 6 is a perspective view of the chair shown in isolation, in a
deconstructed
condition; and
Figure 7 is a perspective view of an edge of a concrete component with the
anchor
embedded therein.
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Detailed Description
With reference to Figure 1, there is shown an anchor 10 for use in lifting a
concrete
component 12 (Fig, 7). The anchor 10 shown is in the form of an edge lift
anchor,
however it will be appreciated by those skilled in the art that alternative
examples of the
present invention may be in the form of other types of anchors such as, for
example, a face
lift anchor.
The anchor 10 comprises a single length of wire 14 bent to form a head portion
16
engagable with a clutch of a lifting system, and a body portion 18 for
embedment with the
concrete component 12. The wire 14 is bent such that opposed legs 20, 22 of
the body
portion 18 extend in a plane substantially perpendicular to a plane of the
head portion 16.
By virtue of the wire 14 being bent in this way, the anchor 10 is able to be
arranged such
that the opposed legs 20, 22 lie in a plane substantially parallel to a
central plane of the
concrete component 12, while the head portion 16 is oriented substantially
perpendicularly
to the central plane of the concrete component 12. Advantageously, this
enables the
anchor 10 to be located lower in the concrete component 12 to facilitate edge
lifting of the
concrete component 12, while facilitating a broad spread of the opposed legs
20, 22 within
the concrete component 12.
As the legs 20, 22 are spread outwardly from a central axis 24, the load
applied to
the anchor 10 is distributed through a larger region of the concrete component
12 than is
possible with a typical concrete anchor having parallel legs. Accordingly,
this reduces the
likelihood of the concrete component 12 failing during lifting, as a large
region of the
concrete component 12 must fail for the anchor 10 to be torn out during
lifting. Each of
the legs 20, 22 may be formed with a wave-like configuration by incorporating
a series of
ripples to provide additional anchorage of the anchor 10 within the concrete
component 12.
Advantageously, the ripples inhibit withdrawal of the legs 20, 22 from the
concrete, by
applying compression to the concrete during lifting. As such, the opposed legs
20, 22 are
able to provide the same function as ancillary tension bars which have been
used in
existing lifting anchors.
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To achieve the perpendicular configuration, the head portion 16 in the example
shown is twisted through an angle of 270 degrees relative to the body portion
18 about the
central axis 24 of the anchor 10. In alternative anchors, to achieve a
perpendicular
configuration the head portion may be twisted through an angle of 90 degrees
(or, more
generally, an angle of 90 + 180x, where x is a non-negative integer) relative
to the body
portion 18 about the central axis 24 of the anchor 10. The central axis 24 is
in the plane of
the head portion 16. In this way, the plane of the head portion 16 is
perpendicular to the
plane of the body portion 18.
It will be understood that, in alternative examples, the body portion 18 may
be
rotated about the central axis 24 relative to the head portion 16 such that
the plane of the
body portion 18 is out of the plane of the head portion 16 by an angle other
than 90
degrees. In particular alternatives, this angle may be approximately 60, 45,
30 or 15
degrees, as may be appropriate depending on the shape and/or orientation of
the concrete
component 12.
The anchor 10 may be used for lifting concrete panels with varying edge
profile
angles by, prior to embedment of the anchor 10 within the concrete panel,
bending the
head portion 16 out of the plane of the legs 20, 22 by a corresponding angle.
This bending
may be effected on site to suit the particular application. For example, where
the edge
profile of the concrete panel is angled at 15 degrees, the head portion 16 of
the anchor is
correspondingly bent upwards at an angle of 15 degrees relative to the plane
of the legs 20,
22. Similarly, where the edge profile of the concrete panel is angled at 45
degrees, the
head portion 16 of the anchor 10 is bent upwards to a corresponding angle of
45 degrees
relative to the plane of the legs 20, 22. It will be understood that the angle
to which the
head portion is bent relative to the plane of the legs 20, 22 may vary between
0 and 90
degrees, however the most common angles of edge profiles are 9 degrees, 15
degrees, 22.5
degrees, 30 degrees and 45 degrees.
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The anchor 10 includes a collar 26 adapted to fit around the head portion 16,
as
shown in Figure 1. The collar 26 forms abutment shoulders 28 at upper and
lower
locations of the head portion 16 for cooperation with a body of the clutch to
limit clutch
rotation relative to the anchor 10.
More specifically, the collar 26 includes an attachment portion 58 for
attaching the
collar 26 to the lifting anchor 10, and an abutment portion 60 adapted to
provide a clutch
abutment surface for limiting rotation of a clutch relative to the lifting
anchor 10. The
attachment portion 58 is arranged for attaching the collar 26 to the head
portion 16 of the
lifting anchor 10. When the collar 26 is fitted to the anchor 10, the clutch
abutment surface
is formed as an abutment shoulder 28 standing proud of each opposed surface or
side of
the head portion 16 for limiting rotation of the clutch about an eye 62 of the
head portion
16, in both directions of rotation. The collar 26 may include a gap 64 between
the
shoulders 28 which coincides with the eye 62 of the head portion 16 to allow
passage of
the clutch through the eye 62.
The collar 26 is generally C-shaped, including a pair of clasps for coupling
to those
parts of the head portion defining the opposed surfaces or sides of the head
portion 16,
with a connecting strip 66 between the clasps. Each clasp terminates in a tab
68 which
secures the collar 26 to the head portion 16 by way of a hard press fit. The
abutment
portion 60 is formed by an edge of the collar 26, at each of the clasps.
The collar 26 includes a pair of shear bars 30, 32 attached to the collar 26.
The
shear bars 30, 32 extend generally perpendicularly to the central axis 24 and
transverse to
the plane of the body portion 18. These shear bars 30, 32 assist in preventing
shear failure
of the concrete component 12 during lifting, and provide improved anchorage of
the
anchor 10 within the concrete component 12. Each of the shear bars 30, 32 is
formed in a
generally wave-like shape, with lateral oscillations 34 in a direction
generally
perpendicular to the central axis 24 of the anchor 10. A second one of the
shear bars 30 is
located adjacent a first one of the shear bars 32, and is reversed such that
the second shear
bar 30 is substantially a mirror image of the first shear bar 32 when viewed
from an end of
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the anchor 10. The shear bars 30, 32 may be positively held in place relative
to the head
portion 16 by engagement of the shear bars 30, 32 within grooves 36 formed in
the collar
26. The grooves 36 formed on opposite sides of the collar 26 may be formed in
a
correspondingly offset configuration so as to positively locate the shear bars
30, 32 in the
arrangement shown. Alternatively, the shear bars 30, 32 may be fixed relative
to the head
portion 16 by spot welding of the shear bars 30, 32 to the collar 26.
The applicant has determined that the collar 26 is particularly suited for use
in
providing a concrete component lifting anchor formed of bent rod or wire with
clutch
abutment surfaces for limiting rotation of a clutch relative to the lifting
anchor. This is
because there is not the same ability in providing anchors formed of bent wire
with
shoulders as there is with anchors cut from plate. However, it is possible for
collars
formed in accordance with other examples of the present invention to be used
with anchors
formed from plate, and such collars may provide various advantages over cut
abutment
shoulders. In particular, using a collar according to an example of the
present invention
provides the ability to interchange collars to change the size/shape of
abutment shoulders,
and provides a convenient way to attach shear bars to the anchor.
The collar 26 is preferably formed of metal, in particular from folded steel.
In
other examples, the collar may be formed from plastic.
Returning to the actual anchor itself, the length of wire or rod 14 from which
the
anchor 10 is formed from a one-piece elongate element shaped into the desired
shape.
More particularly, the anchor 10 is formed from a length of metal rod which is
bent to
form the anchor 10. The length of metal rod may be drawn from a coil.
Advantageously,
by virtue of the anchor 10 being formed from metal bar, material wastage is
minimised,
and the anchor 10 is manufactured in a particularly cost-effective manner.
In particular, the head portion 16 is formed by bending the metal rod around a
forming piece (nor shown), the forming piece being a pin having a size
corresponding to
the size of a clutch portion to pass through the head portion 16. By virtue of
this forming
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process, any variation in the dimensions (particularly the diameter) of the
metal bar will
not alter the size of the aperture in the head portion 16. Accordingly, it is
possible to
provide a superior tolerance for an effective, rigid coupling between the
clutch and the
anchor, thus avoiding a sloppy coupling between the anchor and the clutch. In
other
words, variation in the rod does not affect quality of engagement between the
anchor and
the clutch.
Also, by virtue of the anchor 10 being formed from round cross-section metal
rod,
there is a single point of contact between the clutch portion and the anchor
10, avoiding the
problems associated with skewed prior art anchors cut from metal plate which
tend to
transfer undesirable forces to the concrete component 12.
With reference to Figure 2, the anchor 10 forms part of an anchor assembly 38
which includes a chair 40. The chair 40 comprises an upper, part 44 and a
lower part 46
which are fitted together, with the upper part 44 having clips 48 for holding
the anchor 10
in place relative to the chair 40, as shown in Figures 3 to 5. Figure 6 shows
a detailed view
of the upper part 44 and the lower part 46 in isolation. As the body portion
18 is in a plane
perpendicular to the plane of the head portion 16, when in situ the opposed
legs 20, 22 do
not extend below the head portion 16, thus allowing the anchor 10 to be
mounted in a
relatively low position within the concrete component 12, while ensuring the
opposed legs
20, 22 are embedded inside the concrete component 12. More particularly, the
chair 40 is
arranged for supporting the anchor 10 within the concrete component 12, with
the plane of
the body portion 18 coplanar or oriented substantially parallel to a central
plane of the
concrete component 12.
By virtue of the plane of the body portion 18 being coplanar with or
substantially
parallel to a central plane of the concrete component 12, it is possible for
the body portion
18 to be located at or within a neutral axis of the concrete component 12 so
as to avoid
having the anchor embedded in regions of the concrete component 12 which are
under
high compression and/or tension during lifting. This may assist in avoiding
failure of the
concrete component 12 during lifting, and may enable lifting of concrete
panels at a stage
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more premature (relative to the time of casting) than is required for lifting
using existing
concrete anchors.
Furthermore, the feature of the plane of the body portion 18 being coplanar
with or
substantially parallel to the central plane of the concrete component 12
enables the anchor
to be used with concrete panels much thinner than is required for lifting.
using existing
concrete anchors which extend transversely across a substantial portion of the
thickness of
the panel.
Figure 7 shows an edge of a concrete component 12 in which the anchor 10 is
embedded. A void 56 is formed around the head portion 16, and facilitates
engagement of
a clutch with the anchor 10 for lifting of the concrete component 12. Although
in this
drawing the anchor 10 is shown as being mounted in a central part of the
concrete
component 12, it will be appreciated by those skilled in the art that the
anchor 10 may be
mounted within the concrete component 12 in a lower location such that the
plane of the
body portion 18 is below the central plane of the concrete component 12.
While various embodiments of the present invention have been described above,
it
should be understood that they have been presented by way of example only, and
not by
way of limitation. It will be apparent to a person skilled in the relevant art
that various
changes in form and detail can be made therein without departing from the
scope of the
invention. Thus, the present invention should not be limited by any of the
above described
exemplary embodiments.
In particular, although the example anchor depicted in the drawings has an
angle
between the plane of the legs and the plane of the head portion of
approximately 90
degrees, it will be understood that in alternative examples the angle between
the plane of
the legs and the plane of the head portion may take other values, for example
60, 45, 30 or
15 degrees. This angle may be dictated by the shape and/or orientation of the
concrete
component.
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The reference in this specification to any prior publication (or information
derived
from it), or to any matter which is known, is not, and should not be taken as
an
acknowledgment or admission or any form of suggestion that that prior
publication (or
information derived from it) or known matter forms part of the common general
knowledge in the field of endeavour to which this specification relates.
Throughout this specification and the claims which follow, unless the context
requires otherwise, the word "comprise", and variations such as "comprises"
and
"comprising", will be understood to imply the inclusion of a stated integer or
step or group
of integers or steps but not the exclusion of any other integer or step or
group of integers or
steps.
