NZ620976B2 - An anchor with a roll-bar - Google Patents
An anchor with a roll-bar Download PDFInfo
- Publication number
- NZ620976B2 NZ620976B2 NZ620976A NZ62097612A NZ620976B2 NZ 620976 B2 NZ620976 B2 NZ 620976B2 NZ 620976 A NZ620976 A NZ 620976A NZ 62097612 A NZ62097612 A NZ 62097612A NZ 620976 B2 NZ620976 B2 NZ 620976B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- fluke
- anchor
- shank
- roll
- length
- Prior art date
Links
- 241000935974 Paralichthys dentatus Species 0.000 claims abstract description 136
- 108060002965 flK Proteins 0.000 claims abstract description 136
- 239000011888 foil Substances 0.000 claims abstract description 16
- 210000001699 lower leg Anatomy 0.000 claims description 102
- 210000003414 Extremities Anatomy 0.000 claims description 9
- 229910000742 Microalloyed steel Inorganic materials 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 239000000956 alloy Substances 0.000 claims description 2
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 claims description 2
- 229910001039 duplex stainless steel Inorganic materials 0.000 claims description 2
- 230000000149 penetrating Effects 0.000 claims description 2
- 210000000474 Heel Anatomy 0.000 description 9
- 238000005452 bending Methods 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 239000002689 soil Substances 0.000 description 6
- 238000004873 anchoring Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006011 modification reaction Methods 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 229910001335 Galvanized steel Inorganic materials 0.000 description 1
- 230000001668 ameliorated Effects 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000003247 decreasing Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000008397 galvanized steel Substances 0.000 description 1
- 238000001513 hot isostatic pressing Methods 0.000 description 1
- 230000002452 interceptive Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002829 reduced Effects 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 230000002441 reversible Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 230000003068 static Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/24—Anchors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/24—Anchors
- B63B21/30—Anchors rigid when in use
- B63B21/32—Anchors rigid when in use with one fluke
Abstract
anchor 1 having a roll-bar 43 positioned substantially above the upper surface of the fluke 3, the roll-bar 43 forming a semi-circular or elliptical wheel spanning the maximum width of the fluke 3. The cross section of at least a substantial part of the length of the roll-bar 43 is substantially in the form of a foil or wing. in the form of a foil or wing.
Description
Title
An Anchor With a Roll-bar
Field of the Invention
The invention relates to An Anchor With a Roll-bar
Background of Invention
The art of marine anchors has progressed to the point where one-sided designs are accepted
as superior configurations in the interest of a balance of performance and strength. Anchors
of this configuration termed asymmetrical anchors typically have a single fluke with one side
of the fluke intended to meet the soil of the seabed. Such anchors have proven to be more
efficient than symmetrical designs by way of both setting into the seabed more reliably, and
generating a higher resistance for holding on a weight-for-weight basis, whilst being better
suited for a construction that is strong and durable. It is also the case that the largest portion
of demand is for drag embedment anchors, which are the usual choice for temporary
anchoring as opposed to permanent mooring. Because of their nature, asymmetrical drag
embedment anchors must necessarily orient themselves, after being dropped onto the seabed,
into the correct attitude for which they are designed to set into the seabed in response to a
pull on the anchor rode by the anchoring vessel. If this self-orientation does not occur, the
anchor may in some circumstances rest on its back or its side and never present its fluke to
the seabed. In such cases the anchor fails in its purpose. This self-orientation must be
reliable, work across a large range of seabeds, and must also work if the anchor is pulled out
of the seabed by way of a reversal or veer of the direction of pull on the anchor rode. Should
this occur the anchor is expected to re-set itself without manual intervention. The two main
methods of ensuring this self-orientation hitherto have principally been the attachment of a
roll-bar to the rear of the fluke or the adding of weight ballast to the tip of the anchor. Other
attempts have been made by shifting the position of the shank on the fluke and adding
complex protrusions such as fins above the working surface of the rear of the fluke. Such
constructions have inherent failings or disadvantages.
The shank of the anchor forms a lever which is subjected to forces applied from the rode
attachment point and is therefore vulnerable to deformation or bending at or around the base
if the fluke of the anchor is held firmly. This lever is necessary for temporary drag
embedment anchors because the fluke must be able be aligned correctly by the rode’s pull
alone. High forces in normal usage will subject the shank to linear pulls. The highest forces
are likely to be when the anchor is being retrieved, and is very well set and buried, or is
fouled (stuck) on some obstacle. In this case the vessel may exert extremely high forces in an
upward direction on the shank. A problem with existing anchors is that the shank is formed
from a variant of either a flat plate with substantially even thickness or a simple I-beam. The
former lacks strength on a weight-for-weight basis and the latter restricts burying
performance of the anchor. This is clearly disadvantageous.
Also the anchor fluke is vulnerable to bending or deformation in two principle locations:
firstly where the shank is mounted and forces from the rode are thereby transmitted, and
secondly at the tip which is the first to encounter the seabed and may be subjected to hard
rock or other underwater obstacles. This also is disadvantageous.
Another problem relates to performance as measured by setting effectiveness and ultimate
holding capacity. The anchor shank and fluke may be constrained by geometry enforced by
plate construction methods that result in a sub-optimal fluke surface area or higher mass than
desirable. In turn this means a less efficient anchor on a weight-for-weight basis. This is
disadvantageous to anchoring performance.
Existing anchors that self-right without the use of a roll-bar may make use of fins, modified
skids, or other protrusions raised above the fluke surface. These protrusions collect soil from
the seabed substrate in which the anchor is used, which may be compacted by the pressure of
normal anchoring activity. This can alter the anchor’s weight balance to the point it does not
self-right as designed if the anchor is later pulled free from the seabed. Without self-righting
the anchor cannot be relied upon to re-set. This is clearly disadvantageous.
Other anchors that self-right without the use of a roll-bar may make use of protrusions again
extending from the rear or side of the fluke which are intended to interact dynamically with
the seabed as the anchor is dragged, providing a rolling moment by way of deflecting soil.
These designs do not self-right when the anchor is static but depend upon the proper
combination of drag speed and ideal seabed conditions, which is clearly disadvantageous as
such a combination may not be counted upon.
Additionally existing anchors that self-right without the use of a roll-bar make use of either a
large amount of dead weight as ballast or place the shank impractically far forward on the
fluke. The former makes the anchor less efficient on a weight-for-weight basis, and the latter
causes both bow-roller compatibility problems and leaves the majority of the fluke
unreinforced and subject to damage. These constructions are both disadvantageous.
Existing anchors that self-right by way of a roll-bar have hitherto made use of solid round
bar or hollow tube. Solid bar is either too thin to reliably keep the rear of the anchor when
upside-down from sinking into a soft seabed, or unnecessarily heavy if made of larger bar
diameter. Alternatively a hollow tube may fill with mud entering by way of the openings
which cannot be sealed if the anchor is to be hot dip galvanized. Neither method provides
any further benefit once the roll-bar has performed its function of orienting the anchor to the
correct attitude for setting. This is disadvantageous.
Furthermore anchors may sink some distance into the seabed when the rear edge of the fluke
digs into the seabed. This reduces the ability of the anchor to roll into the correct attitude for
effective use. Again this is disadvantageous.
Prior References:
All references, including any patents or patent applications cited in this specification are
hereby incorporated by reference. No admission is made that any reference constitutes prior
art. The discussion of the references states what their authors assert, and the applicants
reserve the right to challenge the accuracy and pertinency of the cited documents. It will be
clearly understood that, although a number of prior art publications may be referred to
herein; this reference does not constitute an admission that any of these documents form part
of the common general knowledge in the art, in New Zealand or in any other country.
Definitions:
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed
with either an exclusive or an inclusive meaning. For the purpose of this specification, and
unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning – i.e. that it will
be taken to mean an inclusion of not only the listed components it directly references, but
also other non-specified components or elements. This rationale will also be used when the
term ‘comprised’ or 'comprising' is used in relation to one or more steps in a method or
process.
Object of the Invention
It is an object of the invention to provide an anchor that ameliorates some of the
disadvantages and limitations of the known art or which will at least provide the public with
a useful choice.
Summary of Invention
In a first aspect the invention resides in an anchor including a shank, the shank in transverse
cross section along at least part of the length of the shank having a forward facing edge, a
rearward facing edge and a pair of side faces between the forward facing edge and the
rearward facing edge, the parts of the shank adjacent the forward facing edge being
substantially “v” shaped in cross section and at least part of the side faces between the
substantially “v” shaped part and the rearward facing edges being concave on each side face.
Preferably the “v” shape and the concave parts extend substantially the full length of the
shank.
Preferably the “v” shaped part extends inwardly of the shank substantially one third of the
width of the shank.
Preferably the concave parts of the side faces are positioned so that the shank between the
substantially “v” shaped part and the rearward facing edge is substantially in the form of an
“I” section along at least a substantial part of the length of the shank.
Preferably the concave areas are curved in transverse cross section.
Preferably the edge of the shank formed by the point of the substantially “v” shape is
substantially sharp or is radiused.
In a second aspect the invention resides in an anchor including a fluke having a forward end
and a rearward edge in normal use, the rearward edge having a continuous flange extending
therefrom over at least a substantial part of the rearward edge.
Preferably the fluke includes side edges between the rearward edge and the forward end, the
flange extending onto the side edges.
Preferably the fluke has the upper surface thereof forming a generally concave triangular
spoon shape, with the point of the triangle facing forward and the section of the fluke
adjacent the point of the triangle having an average thickness of which is greater than the
average thickness of fluke adjacent the rearward end of the fluke.
Preferably skids are provided on both sides of the back side edges of the rearward edge of
the fluke at an angle between a range of 70 and 110 degrees to the surface of the fluke at the
location where the skids meet the rearward edge of the fluke.
Preferably the rear of the rearward edge of the fluke is curved or bent upward.
Preferably the anchor further includes a shank, the shank having a substantially forward
facing edge and a substantially rearward facing edge in normal use, the flange and the shank
each being curved along their length such that in use the shank and flange co-operate to
allow the anchor to rotate about the flange and at least parts of the rearward facing edge.
Preferably the angle between the flange and the fluke at their intersection is between
substantially 60° and substantially 120°.
Preferably each side of the back edges of said fluke possess a quasi-elliptical or circular
convex profile, and the centre of said back edge is located at a point extended behind the
sides of the fluke, and a flange is attached to the back of said fluke, said flange extending
substantially around the width of the fluke, and a shank, wherein the upper edge of said
shank forms a compound curve extending away from a line between the base of the shank
and the rode attachment point, along which said flange and said shank edge the anchor may
roll if positioned on a flat surface in an upside-down or sideways attitude, said surface
always only in contact with one point on said flange and one point of said shank edge such
that the relative position of the anchor’s centre of mass will cause the anchor to rotate until
its tip is also in contact with said surface.
Preferably the flange consists substantially of a surface formed by numerous profiles of
angles selected from a range of angles, said profiles being coplanar to the seabed or curving
away from the seabed in use and forming an average angle of incidence with the seabed in a
range of 0 to 30 degrees when the anchor is in such a position that the seabed is in contact
with the given profile and the upper edge of the shank.
Preferably the fluke has forward and rearward ends in normal use and being substantially
triangular in shape, the fluke having upper and lower surfaces, the upper surface being
substantially concave in transverse cross section and the shank extending from the upper
surface, the fluke having a downwardly extending bulb on the lower surface positioned at or
towards the forward end to provide ballast to the anchor forming a geometry that allows the
centre of mass of the anchor to be lowered in normal use of the anchor, as far as possible.
Preferably said fluke has a downwardly extending part and said bulb is formed by
concavities placed on both sides of the downwardly extending part, which concavities extend
substantially along the length of said downwardly extending part.
Preferably the anchor has a shank.
Preferably the fluke has a tip ballast contained within a volume formed on each side of the
fluke by a line extending from the tip of the fluke to the outer most extremity of one side of
the fluke, the underside front edge of the fluke being at a selected angle to maximise both
setting performance and strength.
Preferably the angle is between substantially 15 and substantially 40 degrees from the line of
the top centre of the fluke’s front section, and said line of the top centre of the fluke’s front
section.
In a third aspect the invention resides in an anchor having a roll-bar positioned substantially
above the upper surface of the fluke, the roll-bar forming a semi-circular or elliptical wheel
spanning the maximum width of the fluke and wherein along at least a substantial part of its
length the roll-bar is in cross section substantially in the form of a foil.
Preferably the upper section of said roll-bar takes the form of a foil or wing with the chord of
said foil or wing being angled within 40 degrees of parallel to the average surface of the
fluke.
Preferably the foil has the surface thereof having the greater radius of curvature facing the
fluke.
Preferably the lower surface of the fluke has a rebate extending from the rearward end to a
position between the forward end and the rearward end.
Preferably the rebate extends substantially one third of the length of the fluke.
Preferably the rebate extends over substantially the full width of the fluke.
Preferably various attachment points are formed by holes penetrating the shank from side-to-
side and said holes are surrounded by a section of shank the thickness of which is equal to
the maximum width of the shank profile at that point in the shank’s length.
Preferably the base of the shank or a section near it is generally thicker than the rode-
attachment end, and said thickness varies between the two ends forming an approximately
linear taper.
Preferably a hole is located in the fluke behind the tandem anchor attachment point on the
shank so positioned that the centre of said hole is near or on an imaginary line from the rode
attachment point extending through the tandem anchor attachment point.
Preferably the profile of the base of the shank is higher than the rode-attachment end, and
said height varies between the two ends forming an approximately linear taper.
Preferably at least the shank is produced with a HSLA (high strength low alloy) or
microalloyed steel or a duplex stainless steel.
Preferably the fluke has a forward end, a rearward end, a lower surface, an upper surface,
and a pair of side edges, a rib substantially longitudinal of the fluke on the lower surface of
the fluke, and the fluke being substantially concave between the rib and the side edges along
at least a substantial part of the length of the rib, the rib extending from the forward end of
the fluke towards the rearward end of the fluke for at least one half of the length of the fluke.
Preferably the fluke has a section of deepened profile extending from the forward end of the
fluke to a position substantially two-thirds of the length of said fluke, or alternately to such a
length that it extends just past the rear extremity of the base of the shank attached above to
the upper surface of said fluke.
Brief Description
The invention will now be described, by way of example only, by reference to the
accompanying drawings:
Figure 1 is a perspective view of an anchor in accordance with a first preferred embodiment
of the invention,
Figure 2 is a side elevation of the anchor of figure 1,
Figure 3 is an enlargement of the part circled in figure 1,
Figure 4 is a cross section on A-A in figure 2,
Figure 5 is a cross section on B-B in figure 2,
Figure 6 is a rear perspective view of an anchor in accordance with a second preferred
embodiment of the invention,
Figure 7 is a side elevation of the anchor of figure 6,
Figures 8a and 8b are alternative cross sections on C-C in figure 7, and
Figures 9 and 10 show the embodiment of the invention shown in figures 6 to 8 in a rolling
motion.
Description of the Preferred Embodiment(s):
The following description will describe the invention in relation to preferred embodiments of
the invention, namely an anchor. The invention is in no way limited to these preferred
embodiments as they are purely to exemplify the invention only and that possible variations
and modifications would be readily apparent without departing from the scope of the
invention.
Figure 1 shows an anchor 1 designed for maximal efficiency and holding capacity, and
optimal strength.
The anchor 1 includes a shank 2 attached to or combined with a single fluke 3. The fluke 3
has an upper surface 4 and a lower surface 5 as well as a forward end 6 and a rearward end or
heel 7. Side edges 8 and 9 extend between the forward end 6 and the rearward end 7. The
forward end 6 is somewhat pointed and the rearward end 7 wider so that the fluke 3 is
substantially triangular in shape.
The fluke 3 may be “folded” along it longitudinal centre line 10 as can be seen in figure 5.
The angle of the “fold” may be varied to suit conditions and needs but I have found that an
included angle of about 145° is satisfactory.
The upper surface 4 is also desirably concave particularly in the area 11 towards the
rearward end 7. Thus the upper surface 4 is somewhat of a concave and triangular spoon
shaped configuration.
Along at least part of the length and substantially the full length of the shank 2, the shank 2
in transverse cross section (A-A) is shaped such that the shank 2 has a forward facing edge
, a rearward facing edge 16 and a pair of side faces 17 and 18 between the forward facing
edge 15 and the rearward facing edge 16. The parts 19 of the shank adjacent the forward
facing edge being substantially “v” shaped in cross section and at least part of the side faces
17 and 18 between the substantially “v” shaped part 19 and the rearward facing edges being
concave on each side face 17 and 18. The concave side faces 17 and 18 do not have any
substantial change of curvature along their length as can be seen in Fig. 5.
In a preferred construction the upper or outer two-thirds of the shank 2 forms an I-beam
shape with concave walls 17 and 18, and with a V section 19 forming the lower or inside
one-third. The upper cross-bar part 20 of the I-beam shape has flat exterior side wall parts
21 of a selected height whilst the lower cross-bar of same may be laterally terminated in a
point or radius 22 with no flat sidewalls.
The I-beam profile of the upper or outer two thirds of the shank 2 thus provides for greater
efficiency of strength on a mass-for-mass basis when compared to a flat plate or an otherwise
un-profiled bar, particularly when the anchor 1 is subject to normal linear pulls. The
construction also permits a wider profile for the same mass which provides for greater lateral
strength giving better resistance to sideways bending forces. The upper cross-bar of the I-
beam profile is subject to compression while the lower is subject to tension during the
aforementioned linear pulls; therefore the larger upper arm and smaller lower arm described
above is the optimal arrangement.
The V profile given to the lower or inner edge 15 of the shank 2 minimizes resistance created
by the shank 2 when burying into the seabed. The concave walls 17 and 18 of the I-beam
profile further provide for smooth flow of soil or sand along the sides of the shank with
minimal resistance, thereby giving enhanced performance with regard to setting or burial of
the anchor in the seabed.
The shank 2 is optimized to best resist loading, for example during retrieval of the anchor,
while also performing normally at other times. Accordingly the profile height of the anchor
shank varies with a decreased height at the rode attachment point 25 and an increased height
toward or at the shank base 26. The lower arm 23 of the “I” beam forming the shank reduces
in arm height along its length towards its extremity to nil or close thereto. This allows the
material of the “I” beam to be reduced but retains sufficient strength in the shank as the
lower part of the shank is in tension while the upper part of the shank is in compression
during any expected linear high loading.
The I-beam profile gives maximum strength in the areas required.
The shank 2 is further refined with a varied thickness, being generally thinner at the rode-
attachment point 25 and thicker at or toward the shank base 26, forming a linear or
substantially linear taper in the maximum thickness or width of the shank section along the
majority of the shank’s length. This taper may proportionately scale the width of the entire
shank profile, or the inner extremities of the I-beam profile concavities may remain a
substantially constant distant apart while the outer extremities vary their thickness instead.
The bending moment of a beam is proportionate to the square of the beam’s thickness, so
this lateral taper further optimizes strength by providing greater thickness and therefore
strength at the sections nearest the shank base which are at greatest risk of bending.
The arcuate shape of the shank 2 generally takes the form of a crank, which allows the bulk
of the shank to be offset from the fluke so permitting the setting process to be well underway
before the shank must introduce a level of adverse resistance as it collides with the seabed.
This crank is also so-designed to permit the secure storage of the anchor on the bow roller of
a vessel: the crank should reverse the inner edge 15 of the shank 2 such that said edge
running from the rode attachment point 25 curves through an extremity at the shank crank
then runs toward the tip of the fluke 6, creating a forward edge to the base of the shank in an
angle that is obtuse relative to a line from said tip to the forward edge of the bottom of the
base of the shank. This creates a large-scale notch in which a bow roller may rest, so
minimizing vertical movement of the anchor in rough seas.
The shank 2 provides several attachment points, or at least a rode attachment point 25.
These attachment points require reinforcement in order to transfer force loadings into the
shank evenly with minimal focussing of stress. The attachment points may therefore be
surrounded by a section 28 wherein the width of the shank is held at the maximum width of
the shank’s profile at that point in its tapered length. The depth of these sections may be
roughly equal in width to the width of the respective hole or slot 25, 29. Each such section
thus forms an eye merged with the body of the shank appropriate for attachment of shackles,
swivels, or other fittings.
The shank is preferably formed by either casting, forging, or hot isostatic pressing using a
metal that exceeds a yield strength of 400 MPa.
The rearward edge or heel 7 has a straight or convexly curved edge 30. The heel 7 is thinner
in section to the average thickness of the rest of the fluke 3, as both weight and strength is
more desirable toward the tip or forward end 6. To either side of the heel 7, flanges 32 form
substantially flat surfaces extending from each side edge 8 and 9 which drop below the plane
of the fluke 3 at that point, forming skids which keep the back of the fluke 3 raised by
deflecting the seabed material downward when the anchor is dragged. This allows the
forward end 6 to bury whilst holding the heel 7 up, consequently rotating the anchor into the
desired upright attitude.
The fluke 3 includes a rib longitudinal of the fluke 3 on the lower surface of the fluke 3, and
in the preferred form of the invention the fluke 3 is substantially concave between the rib and
the side edges along at least a substantial part of the length of the rib.
To this end the fluke 3 in the embodiment shown in figure 2 may possess a centrally thicker
area and a central rib 35, which is formed by a profile (B:B) featuring a deepened central
section 36 joined to thinner sections 37 by curved profiles which form concave surfaces 38
on either side of the rib 35. This shape moves mass away from the fluke edges 8 and 9
toward the centre for optimal ballast placement and thus performance. Thus the matter of
anchor fluke vulnerability to bending or deformation in the two principle locations discussed
above are ameliorated by this optimization of mass placement which further serves to
concentrate strength in the fluke away from the outer edges and toward the central axis and
the tip where it is most necessary.
The rib 35 preferably runs a length of about two-thirds of the length of the fluke 3, in any
event terminating before or at the forward edge of the heel 7, so keeping weight toward the
forward end or tip 6 of the fluke 3 where weight is desired and away from the heel 7. In any
event, the rib 35 should extend a little past the canter of the shank base 26, and may taper out
at 36 gradually into the heel 7 past the rear extremity of the shank base 26, providing the
benefit of its reinforcement to the area of the fluke 3 to which the shank 2 is attached or
combined.
The anchor 1 further includes a roll-bar 40 positioned substantially above the upper surface 4
of the fluke 3. In the preferred form of the invention the roll-bar 40 is in cross section
substantially in the form of a foil and the foil has the surface thereof having the greater
radius of curvature facing the fluke 3.
Thus fluke 3 may have attached to its heel 7 the roll-bar 40 on which the anchor 1 will roll in
order to self-right. Hitherto round hollow tube has been used to form this roll-bar, giving a
circular transverse profile. In the present invention, this roll-bar 40 shown in Fig 3 forms a
foil or wing 41 with the chord 42 between the leading edge and trailing edge of said foil or
wing substantially parallel with the central axis of the fluke 3.
In use this foil shape will deflect soil in the desired direction when the anchor 1 is dragged.
By the principle of lift this will firstly assist in keeping the rear 7 of the fluke 3 from sinking
in soft seabeds when the anchor is upside-down and has not yet self-righted and secondly
will encourage the anchor to bury more deeply when upright and setting.
The foil shape is only required in the parts 43 of the roll-bar likely to contact the sea bed in
use, usually the top section with reference to the anchor in the orientation shown in fig 2, and
may merge into an elliptical shape 44 in order to minimize resistance to mud flow around the
roll-bar in the sections closer to the fluke. This construction minimizes the fouling effect of
the roll-bar whereby mud or sand is undesirably retained at the back of the fluke and does
not flow through or around, thereby interfering with the rest of the fluke’s behaviour.
The use of a solid roll-bar, as opposed to hollow tube, also avoids problems present in the
prior art when the anchor is manufactured of hot dip galvanized steel: such hollow tube must
be left open to allow for the HDG process, and during use this permits the entry of water and
mud to the inside of the roll-bar where it may remain and eventually cause corrosion damage
to the interior.
In further preferred embodiment shown in fig 7, the anchor is made to self-right and attain
the correct attitude for setting by way of a flange 50 at the rearward end of the fluke 3 along
which the anchor will roll even when deployed on a soft seabed. The flange 50 works in
conjunction with the shank 2, which must have an outside curve 51 also designed to permit
the anchor to roll. Thus the rearward edge 7 of the fluke 3 may have a continuous flange 50
extending therefrom over at least a substantial part of the rearward edge 7. The flange 50
preferably extends onto the side edges 8 and 9 at least a short distance as shown in fig 7.
The shank 2 is curved along its length such that in use the shank 2 and flange 50 co-operate
to allow the anchor 1 to rotate about the flange 50 and at least parts of the outside curve 51 of
the shank 2. By suitably proportioning the length and depth of the flange 50 and the shape of
the shank 2 either the shank 2 or the flange 50 can be in contact with the seabed during the
full or almost full rotation of the anchor in use.
Typically in this construction the angle between the flange and the fluke at their intersection
is between substantially 60° and substantially 120°.
In use then the anchor 1 may then roll on a flat surface when finding itself in an upside-down
or sideways attitude as shown in figure 9. As the combined geometry is such that the seabed
surface 52 is always only in contact with one point on the flange 50 and one point on the
shank edge 51 with the anchor’s centre of mass 53 always offset from the plane defined by
these two points, the anchor 1 will rotate until its forward end 6 is also in contact with the
surface 52 and the anchor 1 thus ready to be set (Fig 10).
The anchor 1, when dropped onto the seabed 52 in an upside-down or sideways attitude, will
therefore be able to self-right itself without the use of either a roll-bar or other undesirable
protrusions above the rear of the fluke, an unnecessarily large amount of ballast in the tip of
the fluke, or a shank mounted impractically close to the forward end 6 of the fluke 2.
A moderate amount of ballast added to the fluke adjacent the forward end 6 may be added if
necessary in order to provide sufficient counter-weight to shift the centre of mass far enough
toward the forward end 6. The ballast can be added in the form of a bulb 55 at the bottom of
the fluke 2, as shown in figure 8a or a deepened section or an added insert substantially as
shown in figure 8b. Other cross sectional shapes could be used but it is desirable that the
shape is such that the added ballast will easily pass through a mud or similar seabed. The
bulb 55 as seen in figures 7 and 8a may have concavities 56 on each side thereof.
The bulb ballast is constrained within an imaginary pyramidal geometry formed on each side
of the fluke by a line extending from the tip of the fluke to the outer most extremity of the
side of the fluke, the underside front edge of the fluke being at an angle chosen to be suitable
for both setting performance of the anchor and strength and preferably measures 15 and 40
degrees from the line of the top centre of the fluke’s front section, and said line of the top
centre of the fluke’s front section. If part of the body of the fluke such as the bulb breaks this
constraint, when in the anchor’s proper setting attitude the tip may be lifted clear of the
seabed and thereby performance would be adversely affected or nullified completely.
Ballast formed by the shaping of bulb 55 moves the ballast downward and away from the
anchor’s centre of mass when compared to a typical “V” form anchor. Although the shift in
position is relatively small shifting the entire weight of the anchor even a small distance can
lead to a substantially improved performance. This improves the leverage the effect of the
ballast in use.
In the preferred form of the invention the flange 50 is positioned to be approximately parallel
to the seabed surface 52 when in contact with it, or curved a little up and away to produce a
convex surface. This shape provides the optimal resistance to sinking upon the anchor 1 first
contacting the surface 52.
This is achieved by identifying the contact point on the shank 2 and the contact point on the
back edge of the fluke 2 for any given attitude where the anchor is lying upside-down or
sideways. These contact point pairs may then be joined by imaginary lines which when
extended past the back edge of the fluke 2 form the profile lines for the optimal flange 50
surface. The flange 50 may then be extended around the width of the rearward edge 7 of the
fluke 2 until it meets the parts of the flange 50 on the side edges 8 and 9 of the fluke 2 which
form in use skids 54 on the sides of the fluke 2 and is merged into skids 54 to form a single
surface.
The fluke may feature a hole 60 positioned directly behind the shank in order to allow the
passage of the rode for a tandem anchor which may be attached to the appropriate point 61
on the shank 2. Hole 60 is substantially in line with an imaginary line 62 drawn from the
rode attachment point 25 and the tandem anchor attachment point 61, and also approximately
at the centre of effort of the fluke 2. This arrangement permits forces from the primary and
tandem rodes together with the reaction force from the anchor’s holding effect to be as
collinear as possible when a tandem anchor is in use, keeping the forces on the anchor in the
correct balance for optimal performance.
Advantages
An anchor is provided in which at least in the preferred form has the advantages that the
anchor can resist forces particularly when retrieving the anchor in a satisfactory manner.
Also bending forces on the fluke are resisted to a substantial degree.
The anchor shank and fluke are both configured to achieve optimal performance and
increased efficiency. The shank and fluke are both optimized for effective setting and the
fluke surface area is able to be maximized without significant detriment to strength.
The anchor may roll to the correct attitude for use in a satisfactory manner in use even on
soft seabeds.
The smooth curvature of the concave faces in the shank allow enhanced soil flow during
setting of the anchor in use and improved stress distribution for lateral loading.
Variations
It will of course be realised that while the foregoing has been given by way of illustrative
example of this invention, all such and other modifications and variations thereto as would
be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit
of this invention as is hereinbefore described.
Claims (13)
1. An anchor having a roll-bar positioned substantially above the upper surface of the fluke, the roll-bar forming a semi-circular or elliptical wheel spanning the maximum width of the fluke and wherein along at least a substantial part of its length the roll-bar is in cross section substantially in the form of a foil or wing.
2. An anchor as claimed in claim 1 wherein the upper section of said roll-bar takes the form of a foil or wing with the chord of said foil or wing being angled within 40 degrees of parallel to the average surface of the fluke.
3. An anchor as claimed in either one of claims 1 and 2 wherein the foil has the surface thereof having the greater radius of curvature facing the fluke.
4. An anchor as claimed in any one of claims 1 to 3 wherein the lower surface of the fluke has a rebate extending from the rearward end to a position between the forward end and the rearward end.
5. An anchor as claimed in claim 4 wherein the rebate extends substantially one third of the length of the fluke.
6. An anchor as claimed in either one of claims 4 to 5 wherein the rebate extends over substantially the full width of the fluke.
7. An anchor as claimed in any one of claims 1 to 6 wherein the anchor has a shank and the base of the shank or a section near it is generally thicker than the rode-attachment end, and said thickness varies between the two ends forming an approximately linear taper.
8. An anchor as claimed in any one of claims 1 to 7 wherein the profile of the base of the shank is higher than the rode-attachment end, and said height varies between the two ends forming an approximately linear taper.
9. An anchor as claimed in any one of claims 1 to 8 wherein various attachment points are formed by holes penetrating the shank from side-to-side and said holes are surrounded by a section of shank the thickness of which is equal to the maximum width of the shank profile at that point in the shank’s length.
10. An anchor as claimed in any one of the claims 1 to 9 wherein a hole is located in the fluke behind the tandem anchor attachment point on the shank so positioned that the centre of said hole is near or on an imaginary line from the rode attachment point extending through the tandem anchor attachment point.
11. An anchor as claimed in any one of claims 7 to 10 wherein at least the shank is produced with a HSLA (high strength low alloy) or microalloyed steel or a duplex stainless steel.
12. An anchor as claimed in any one of claims 1 to 11 wherein the fluke has a forward end, a rearward end, a lower surface, an upper surface, and a pair of side edges, a rib substantially longitudinal of the fluke on the lower surface of the fluke, and the fluke being substantially concave between the rib and the side edges along at least a substantial part of the length of the rib, the rib extending from the forward end of the fluke towards the rearward end of the fluke for at least one half of the length of the fluke.
13. An anchor as claimed in claim 12 wherein the fluke has a section of deepened profile extending from the forward end of the fluke to a position substantially two-thirds of the length of said fluke, or alternately to such a length that it extends just past the rear extremity of the base of the shank attached above to the upper surface of said fluke.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161535370P | 2011-09-16 | 2011-09-16 | |
US61535370 | 2011-09-16 | ||
NZ602454A NZ602454B2 (en) | 2011-09-16 | 2012-09-17 | An Anchor |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ620976A NZ620976A (en) | 2016-10-28 |
NZ620976B2 true NZ620976B2 (en) | 2017-01-31 |
Family
ID=
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