DK176364B1 - Marine drag anchors, is constrained by the inclusion of structural adaptation which enables the self penetration through the surface of the mooring bed - Google Patents

Abstract

The drag anchor has values of angles a and b which exceed the danforth It progressively buries it self in the sea bed surface when dragged. The drag anchor is constrained by the inclusion of structural adaptation which enables the self penetration through the surface of the mooring bed. DETAILED DESCRIPION - The marine anchor is driven vertically into a mooring bed(10) by an elongate follower (13). The follower has a bottom clevis part (103) which has been adapted to hold the anchor (1) via the anchor shank (2). When the anchor is embedded to a preferred depth, the anchor is moved into position by pulling the on the anchor cable (4/4a) which causes the shear pin to fracture and the anchor to rotate until arrest by a stop on the follower.

Description

1 DK 176364 B1

The present invention relates to an anchoring device comprising a ship anchor and anchor embedment means comprising an elongate follower member releasably attached to the anchor and adapted to push the anchor into a mooring base, and a method of laying an anchor.

A ship anchor for embedding in a mooring base is generally attached to a 10 anchor rope for connection to an object to be secured by mooring in a watershed above the mooring base. The anchor has a load supply point for attaching the anchor rope thereto via an anchor rope fastener (for example, a shackle) and an anchor tab member and has a symmetry plane containing a first direction in which the surface of the anchor tab element is viewed from the load supply point when the anchor is in use. , has a maximum projected area and another (forward) direction (F) in which said surface has a minimum projected area. Similarly, in these directions maximum and substantially minimal resistance to movement of the anchor occurs in a mooring ground layer. The anchor tab tends to move forward in the ground along the forward direction (F) with minimal resistance.

A towing bearing anchor is a ship anchor as described above, where the loading point of the anchor rope attachment means is located on the anchor such that tension horizontally in the rope with the anchor lying on the surface of a mooring support causes the anchor to tilt into penetrating engagement therewith and thereby down into the mooring base with a significant displacement component acting in the forward direction with minimally projected area of the anchor tab element surface. This causes the anchor to follow a curved burial path when embedded in the mooring bed. Thus, the location 30 of the load supply point allows the anchor rope fastener to act as the anchor embedding member.

f 2 DK 176364 B1

A direct embedding anchor, see, for example, EP-A-0 161 190, is a ship anchor as described above having a load supply point for the anchor rope fastener located so that pulls in the attached anchor rope 5 cause the anchor to seek to move in the direction of maximum projected area of the anchor tab element when buried in the mooring base. This causes the embedded anchor to follow a path which rises to and breaks out through the surface of the mooring bed, thus preventing the anchor rope and the anchor rope attachment means from acting as the anchor means for the anchor.

Therefore, an alternate embedding means comprising a pushing element known as a follower is used to engage with and push the anchor deep into the mooring base substantially in the forward direction with minimal projected area of the anchor tab member.

Each aforementioned anchor will hereinafter be referred to as, respectively, a ship's anchor, a towed anchor or a direct bearing anchor of the type described above.

These anchors have disadvantages: the drag bearing anchor requires a sometimes unacceptable horizontal displacement component to reach a desired embedment depth below the surface of a mooring, and the direct bearing anchor suffers from a progressive decreasing bearing depth when overloaded, which eventually results in to break out of the mooring ground. Furthermore, the direct embedding anchor requires it to be pushed down into the seabed by a long follower that is prone to damage and is difficult to handle when applied to the deck of an anchor-handling vessel.

30 3 DK 176364 B1

The object of the invention

The objects of the present invention include, among other things, reducing these disadvantages. The present invention generally provides an anchoring device comprising a ship anchor following a burial trajectory when being towed by an anchor rope via an anchor rope fastener after it is embedded in an initial buried position beneath the seabed surface, and a embedding means for establishing the initial buried position.

According to a first aspect of the present invention, a ship anchor as described herein and in an operating design for use below the surface of a mooring base is a tow anchor, characterized in that a straight line containing the load supply point and the geometric center of gravity of the anchor tab element surface is viewed from the load point. , forms a forward opening angle 15 (β) with the forward direction (F) in the range of 68 ° to 85 ° for use in soft cohesive soil and in the range of 50 ° to 65 ° for use in non-cohesive soil, whereby a traction force, applied to the anchor of the anchor rope at the load application point of the anchor rope attachment, when the geometric center of gravity of the anchor flap is buried at least twice the square root of the maximum projected area below the surface of the mooring bed, the anchor causes it to move in the ground a significant displacement component in the a nnd forward direction.

Preferably, the significant shear component in the second forward direction exceeds 35% of the actual shear.

Further preferably, the significant shear component in the second forward direction exceeds 50% of the actual shear.

Preferably, the angle of the geometric center of gravity does not exceed 80 ° for use in soft cohesive soil and does not exceed 60 ° for use in non-cohesive soil.

, DK 176364 B1

Preferably, the tow anchor is further characterized in that a plane perpendicular to the plane of symmetry of the anchor, which contains a forward end of the anchor tab member and the load point, forms a forward opening angle (a) with the forward direction (F) not less than 95. ° for use in soft cohesive soil and not less than 85 ° for use in non cohesive soil.

Preferably, said point angle is not less than 100 ° for use in soft cohesive soil and is not less than 90 ° for use in non cohesive soil.

10

Preferably, the tow anchor according to the first aspect of the present invention comprises an anchor tab with a plate-like shank member rigidly attached thereto, which is parallel to said plane of symmetry.

Preferably, the plate-like shank member includes an elongated slit for slidable movement therein of an anchor rope fastener, a front end of the slot serving as a loading point for the anchor rope allowing deeper burrowing of the anchor by towing, and with a back end. is disposed towards a trailing edge of the anchor tab, which serves as a replacement load supply point for the anchor rope fastener which allows easy backward salvage of the anchor in a direction substantially opposite to said forward direction.

Preferably, a sliding stop means is provided immediately behind the front end of the slot to hold the fastener at said load supply point.

Preferably, the slide stop means includes a release member which cooperates with the anchor rope fastener, whereby rotational displacement of the fastener releases the slide stop means to allow the fastener to slide into the slot toward the rear of the anchor tab.

. DK 176364 B1 o

Preferably, the anchor rope attachment means comprises an elongated shackle.

Further preferably, the anchor rope attachment means comprises an elongate element having a point of attachment at one end which serves to connect to an anchor rope and with a tow bar at another end which carries a bolt member which serves to engage slidably and pivotally in the slot. in the shaft member.

Preferably, the shank member includes a curved surface centered on the load supply point and the elongate member includes a stop which can be slidably engaged on the curved surface, whereby the bolt member is held at the load supply point in the slot until rotation of the elongated member the load supply point brings the direction of movement of the stop parallel to the slot, whereby the bolt member can freely slide into the slot.

15

Preferably, the anchor includes a releasable pivot stop means which stops rotation of the elongate member at a predetermined position relative to the shaft member when the bolt member is at said load supply point.

Preferably, the elongate member is of such length that when the member is stopped from rotating the releasable pivot stop member, a plane perpendicular to said plane of symmetry, forming a forward end of the anchor tab member and the attachment point of the elongate member, forms a forward angle with the other direction not exceeding 95 ° and further preferably not exceeding 75 °.

According to another aspect of the present invention, a ship anchor and embedding means comprise one of a towing bearing anchor as described above and towed anchor, and an elongate follower member removably attached thereto and adapted to push the anchor substantially in the other forward position. direction with minimum projected area of the surface of the anchor tab member as viewed from the load point of the anchor rope fastener, until the geometric center of gravity of the anchor tab is at least twice the square root of the maximum projected area below the surface of a mooring underlay, the anchor rope after releasing the tracking element from the embedded anchor causes the anchor to seek to move in the ground in the mooring substrate with a significant displacement component in said second direction.

According to a third aspect of the present invention, a ship anchor and embedding means comprise one of a towing bearing anchor and a direct bearing anchor and a towing anchor as described above and an elongate follower member removably attached thereto and adapted to push the anchor substantially into said second direction down into a mooring ground, characterized in that at least one of the anchor and elongate follower is arranged to provide a reaction pivot around which the anchor can pivot.

15

Preferably, the ship anchor is arranged to pivot around said pivot point when a traction force is applied to the anchor by means of a fixed anchor rope.

Preferably, the embedding means for directly embedding a ship anchor comprises an elongate follower member adapted to provide removable attachment to a ship anchor and a reaction pivot around which the anchor may pivot as it is pushed down into a mooring base of the follower member.

According to a fourth aspect of the present invention, a ship anchor and embedding means comprise a ship anchor as described above and an elongate follower member removably attached thereto and adapted to push the anchor substantially in the other direction and further adapted to bend. recoverable without suffering damage when subjected to transverse forces, for example, due to the passage of a curved surface, such as a stern roll on an anchor handling vessel.

7 DK 176364 B1

According to a fifth aspect of the present invention, an embedding means for directly embedding a ship anchor comprises an elongate follower member adapted for removable attachment to a ship anchor, and further adapted to bend recoverably without suffering damage when subjected to transverse forces, for example due to the passage of a curved surface, such as a stern roller on an anchor handling vessel.

Preferably, the follower member includes a lower end segment attached to a submerged and salvage rope and includes a plurality of body segments supported by the lower end segment.

Preferably, said body segments substantially surround the immersion and salvage rope.

Preferably, said segments fit together by means of a convex projection on a segment which is adjacent to a corresponding concave depression in an adjacent segment.

Preferably, the said immersion and salvage rope forms an axis which passes through the body segments.

Preferably, at least a portion of the rope within the body segments comprises at least one of a panty and a chain.

Preferably, at least part of the rope within the body segments is formed of elastic extensible material such as polyester rope.

When said rope within the body segments is extended under tension when the follower hangs vertically, the rope is preferably prevented from relaxing a rope stop member operating between an upper body segment and the rope, thereby holding the body segments in an axial compression condition which provides the elongated member having a degree of transverse stiffness to withstand bending when the follower is at least partially supported by contact with the seabed surface.

Preferably, the rope stop member on the upper body segment is releasable, whereby the rope, when the follower is pulled up and bent over the curved surface, is released within the follower to allow relative axial movement between the rope and the upper body segment to avoid excessive stretching of the rope due to of bending the follower.

Preferably, the rope stop means is releasable by movement of an actuator which contacts the curved surface.

Preferably, the rope stop means includes a tooth element located on one of the rope and the upper body element which engages a recess in a recess element located on the other of the rope and the upper body segment.

According to a sixth aspect of the present invention, a towing anchor embedding means comprises an anchor rope attached thereto via an elongate rigid member to the anchor rope attachment means, said elongated member having a first attachment point at one end serving to secure the anchor rope. anchor rope attachment, and a second attachment point at another end for attachment to the anchor rope attachment loading point of the anchor and a releasable pivot stop means to hold the elongate member relative to the anchor such that a plane perpendicular to the plane of symmetry containing a forward end of the anchor rope the anchor joint member and the first attachment point, form a forward opening angle with the second direction not exceeding 75 ° to promote penetration into the surface of a mooring base when the anchor is being dragged over, but released by ground load on the anchor flap when the anchor flap becomes is buried in the ground in the mooring ground.

30 DK 176364 B1

Preferably, the elongated rigid member has a tensioning bracket at the second attachment point which carries a bolt member which serves to engage slidably and pivotally in the slot of the towbar shaft member.

5

The drawing

Embodiments of the present invention will now be described by way of illustration with reference to the accompanying drawings, in which:

FIG. 1 shows a vertical side view of a known tow bearing anchor,

FIG. 2 is a front elevational view of the anchor of FIG. 1, FIG. 3 is a top view of the anchor of FIG. 1

FIG. 4 shows the arrangement of the anchor of FIG. 1 in a mooring bed,

FIG. 5 shows a vertical side view of a known direct embedding anchor, 20

FIG. 6 is a front elevational view of the anchor of FIG. 5,

FIG. 7 is a top view of the anchor of FIG. 5, FIG. 8 shows the arrangement of the anchor of FIG. 5 in a mooring bed,

FIG. 9 is a side elevational view of the drag bearing anchor of FIG. 1 and a follower element according to the present invention arranged in a mooring base, 30

FIG. 10 shows a larger scale detail of the anchor and follower of FIG. 9, 10 DK 176364 B1

FIG. 11 is a side elevational view of a tug anchor in accordance with the present invention; FIG. 12 is a front elevational view of the anchor of FIG. 11

FIG. 13 is a top view of the anchor of FIG. 11

FIG. 14 shows the pointer stop detail in FIG. 11 with the shackle stopped, 10

FIG. 15 shows the detail of FIG. 14 with the shackle stop released,

FIG. 16 shows the detail of FIG. 15 with the shank in a position to move past the release stop, 15

FIG. 17 shows a section A-A through the shackle stopper of FIG. 15,

FIG. 18 shows the anchor of FIG. 11 and a follower element of the present invention passing over an aft roller of an anchor handling vessel;

FIG. 19 is a sectional side elevational view of a segment of the tracking element of FIG. 18, FIG. 20 shows a partial section of a fit between adjacent segments in FIG.

18,

FIG. 21 is a top view of the segment of FIG. 18, 30 FIG. 22 shows the anchor of FIG. 11 and a follower element according to the present invention arranged in a mooring base, 11 DK 176364 B1

FIG. 23 shows the rotation of the anchor of FIG. 11 in response to the tracking element of FIG. 22, FIG. 24 shows tightening of the anchor rope for the turned anchor and salvage of the follower element of FIG. 23

FIG. 25 is a top view of the upper end (control) segment of the tracking element of FIG. 23 with a disengaged chain lock mechanism, 10

FIG. 26 shows the control segment of FIG. 25 with the chain locking mechanism engaged,

FIG. 27 is a sectional side elevational view of the control segment shown in FIG. 25, 15

FIG. 28 is a sectional side elevational view of the control segment shown in FIG. 26,

FIG. 29 is an oblique view of an orientation link shown in FIG. 18 in an oriented position forced by pulling over an aft roller on an anchor-20 handling vessel,

FIG. 30 shows, on a larger scale, a lower end segment of the follower element and the anchor of FIG. 22, 25 FIG. 31 shows a partial section B-B through a pivot connection between the lower end segment of the follower element and the anchor of FIG. 25

FIG. 32 shows a partial section C-C of a lubricant passage in the anchor of FIG. 25, 12 DK 176364 B1

FIG. 33 is a partial section D-D of a lubricant passage and outlet openings located on the front edges of the shaft and anchor tab of the anchor of FIG. 25, FIG. 34 shows the anchor of FIG. 11 modified to act initially in the same manner as the anchor of FIG. 1 and subsequently in the same manner as the anchor of FIG. 11th

10 Description of Embodiment Examples

A known tug bearing anchor 1 (Figs. 1, 2, 3) for tug embedding in a mooring substrate comprises a shaft 2 which is connected at one end to a triangular plate-like or leaf-like anchor tab 3 and at the other end to an anchor rope 4. by means of a shackle 5 pivotally secured in a hole 6 in the shaft 2. The anchor tab 3 has a planar shape and the anchor 1 is symmetrical about a plane of symmetry XX containing the center of the hole 6 in the shaft 2 and in the center line 7 of the shaft. anchor tab 3. Center line 7 is parallel to a forward direction F of anchor tab 3, pointing along anchor tab 3 away from the connection between shaft 2 and anchor tab 3.

20

A straight line in the plane of symmetry XX containing the center of the shaft hole 6 and an anterior point of the anchor tab 3 forms a forward pointing angle α with a forward direction F. A straight line in the plane of symmetry XX containing the center of the shaft hole 6 and the geometric center of gravity C for the upper surface of 25 anchor tab 3, a forward-opening geometric center of gravity β forms with the forward direction F of anchor tab 3.

Such a tow embedding anchor is partially disclosed in UK Patent No. 2,674,969 to R.S. Danforth, where the boundaries of α and β are set as 50 ° to 30 ° 80 ° and 25 ° to 55 ° respectively. In UK Patent No. 553,235, Danforth describes the importance of the angles α and β and states that α values exceeding 75 ° give rise to a lack of reliable engagement of an anchor with the surface of a mooring substrate and that β values as high as 65 ° can be used when an anchor is intended to be used only on soft mud bottoms. These Danforth boundaries show that the tow-embedding anchor geometry has so far been limited by the primary requirement of penetrating the seabed surface.

The towing bearing anchor 1 is laid out on the surface 8 (Fig. 4) of the mooring base and is pulled horizontally by the anchor rope 4. At a point angle α less than 75 °, the anchor tab 3 first enters the surface 8 and then the geometric center of gravity of the anchor tab 10 follows a curved path. 9 in the ground 10 in the mooring substrate, which eventually becomes horizontal at a limiting depth d below the surface 8. The considerable horizontal displacement DD (drag distance) involved in obtaining the desired penetration depth is often unacceptable when the space provided is available on the mooring floor is limited.

A known direct embedding anchor 11 (Figs. 5, 6, 7) for direct embedding in a mooring base comprises a triangular plate shank 2 which is connected at one end to a substantially rectangular plate anchor tab 3 and at the other end to an anchor rope. 4 by means of a shackle 5 pivotally secured in a hole 6 in the shaft 2. The anchor flap 3 has a planar shape and the anchor 11 is symmetrical about a symmetry plane XX containing the shackle hole 6 in the shaft 2 and a center line 7 in the anchor flap 3. A forward direction F is parallel to the center line 7 of the anchor tab 3. A straight line in the plane of symmetry XX containing the center of the socket hole 6 and the geometric center of gravity C of the upper surface of the anchor tab 3 form an angle of 90 ° with the center line. 7th

The direct embedding anchor 11 is driven vertically (Fig. 8) down into a mooring base 10 by means of a rigid elongated follower element 13, which is removably attached thereto. The follower element 13 comprises a pile 14 driven by a pile driving hammer 15 which is attached thereto and suspended in a rope 16. Recovery is completed when DK 176364 B1 center in the area C of the anchor tab 3 is at a desired depth d below the surface. 8 of the mooring base. The pile 14 is then disengaged from the anchor 11 by pulling up the rope 16, and an oblique traction applied via the anchor rope 4 causes the anchor 11 to rotate and at the same time displaced upwardly through a distance k, 5 until the working line of a force in the anchor rope 4 passes through the geometric center of gravity C of the anchor flap 3. The direct engagement anchor 11 is now oriented so as to provide maximum resistance to movement induced by tension in the anchor rope 4 at the actually obtained burial depth d minus k.

However, if the anchor rope 4 is loaded more than this maximum resistance, the direct embedding anchor will fail catastrophically by moving in the direction of the anchor rope 4 until it rises upward and erupts from the surface 8 of the seabed.

For this reason, a security installation factor of 2 is generally required for such anchors.

In a first embodiment of the present invention, a tow bar anchor 1 as described above with an angle β (Fig. 1) of a preferred high value is removably and pivotally secured by a pivot pin 17 (Fig. 9) on the shaft 2 to a cooperating drawbar 18 at a lower end 19 of a strong elongate follower 13 suspended in a recess and salvage rope 20 16. The center line 7 of the anchor tab 3 is initially arranged parallel to a longitudinal axis 20 of the follower 13, so that the anchor tab 3 presents minimum projected area in the axis 20 and the center of area C1 (Fig. 2) of the sum of the minimum projected areas of the anchor 1 and the shackle 5 is aligned with the axis 20. Pull in the anchor rope 4 parallel to axis 20 rotates the anchor 1 about 25 pivot 17 until it is stopped by the shaft 2 coming into contact with a stop 21 in the drawbar 18, upon which a desired orientation of the anchor 1 is established. A small securing pin 22 (Fig. 10) passing through the drawbar 18 and the shaft 2 serves to hold the anchor 1 of the drawbar 18 with the center line 7 of the anchor tab 3 parallel to the axis 20 prior to said rotation.

30 ° c DK 176364 B1

Embedding of the anchor 1 (Fig. 9) is accomplished simply by lowering the anchor 1, which is attached to the follower 13 down to the surface 8 of the mooring base 10 and continuing to lay the rope 16, keeping the anchor rope 4 slack. The anchor 1 is pressed down into the mooring base 10 by the weight of the heavy follower 13 until the geometric 5 center of gravity C of the anchor flap 3 is at a desired depth d below the mooring surface 8, which exceeds twice the square root of the maximum projected area of the anchor flap 3. This is achieved by appropriately selecting the mass of follower 13. The rope 16 is then left off and the anchor rope 4 is raised. As follower 13 is in place to provide a response element, 10 causes the hoisting tension in rope 4 to break securing pin 22 (Fig. 10) and anchor 1 to rotate in ground 10 in mooring support around pivot 17 until shaft 2 is stopped by stop 21 Thus, the geometric center of gravity C of the anchor tab 3 moves slightly deeper than the depth d below the surface 8, and the unfortunate loss of burying depth k shown in FIG. 4 is eliminated. The follower 13 is then disengaged from the anchor 1 by lifting the rope 16 and applying an oblique force to the anchor rope 4 causing it to cut into the ground to move the anchor 1 substantially in a forward direction. direction F along a downward sloping path 9, where further embedding of the anchor 1 allows for ever-increasing loads to be maintained in the anchor rope 4. Although the anchor 1 is directly embedded 20 without unwanted horizontal movement, it does not fail catastrophically when overloaded , by moving in the direction of the anchor rope 4 to pull out at the surface 8, but instead moving horizontally at constant load or diving deeper with increased load in a safe manner. Thus, an installation factor of 1.5 accepted for towing embedment anchors may be used in place of a safety factor of 2, usually required by direct embedment anchors known to fail catastrophically. This allows smaller anchors to be used in a given mooring system at a lower cost.

However, the tow embed anchor 1 (Fig. 9) has values of the angles α and β (Figs.

30 1), which lies within the aforementioned Danforth boundaries and thus retains the ability to penetrate into the surface of the seabed when it is dragged horizontally over it. As a result, the shaft is longer than what is needed for progressive burial once the anchor is below the seabed surface. This excess length produces undesirably high penetration resistance when embedded vertically in the seabed and thus requires an unnecessarily heavy follower 13 (Fig. 9).

In contrast, a towing anchor of the present invention has values of angles α and β that exceed the Danforth boundaries and thus do not have the ability to penetrate the surface of the ocean floor when dragged horizontally across it, even if it retains the ability to progress toward being buried. , when it is dragged horizontally from a position already below the surface of the seabed. The tow anchor just described therefore requires only a short compact shaft element and thus provides minima! resistance to being pushed vertically into the seabed by a follower. Furthermore, the high values of angles α and p allow the towing anchor advantageously to follow a trajectory 9 which is much steeper than is possible for the towing embedment anchor limited by the Danforth boundaries.

Thus, both a tow embedding anchor and a tow anchor will be buried as they are towed in a mooring support from a starting position at a given depth below the surface of the mooring support. The tow embedding anchor is limited by the inside end of structural alignment to enable self-penetration through the surface of a mooring underlay. The tow anchor is not subject to such a restriction and in fact the tow anchor is possibly incapable of self penetration through a surface of the mooring base. A ship anchor comprising a tow anchor which is free of said restriction is disclosed in the present invention which enables the realization of hitherto unavailable possibilities.

According to another embodiment of the present invention, a tug anchor 23 (Figs. 11, 12, 13) comprises a design which allows use when placed beneath the surface 8 of a mooring base 10 by a follower 13 (Fig. 22). , 17 DK 176364 B1 is a four-sided steel plate shaft 2, which lies in a plane of symmetry XX in the anchor 23 and is welded at right angles to an upper planar surface 24 of a square steel plate anchor 3 of length L. The average thickness of the shaft 2 and of anchor tab 3 does not exceed 0.04 times (and preferably does not exceed 0.03 5 times) the square root of the maximum projected area of anchor tab 3. The center line 7 of surface 24 lies in the plane of symmetry XX perpendicular to an edge 25 of anchor tab 3 which is sharpened by chamfering to reduce the penetration resistance in the ground.

A load supply and attachment point 26 for a shackle 5 connecting an anchor rope 4 to the shaft 2 is located at an end 27 of the shaft 2 which faces away from the anchor tab 3. The direction from the geometric center of gravity C of the surface 24 along the center line 7 for the sharpened edge 25 determines a forward direction F. A plane containing the pivot attachment point 26 and the sharp edge 25 forms a line of intersection with the plane of symmetry XX which determines a

forward angle α in plane XX with respect to forward direction F. A straight line containing the geometric center of gravity C and shaft attachment point 26 forms a forward opening angle β with respect to forward direction F. The angle α is not less than 95 ° to use of the anchor 23 in soft cohesive soil (clay) and not less 85 ° for use in non cohesive soil (sand), with α preferably not less than 100 ° and 90 ° for soft clay and sand respectively. The angle β can be as close to 90 ° as possible without preventing the anchor 23 from moving in the ground in the mooring substrate 10 with a significant displacement component 9B (Fig. 24) of the geometric center of gravity C occurring in the direction F. The significant component 25 may preferably be considered as not less than 35% of the displacement 9A

in the actual direction of movement, with a further preference of 50%. In practice, however, the angle β (Fig. 11) does not exceed 85 ° for use of the anchor 23 in soft clay and does not exceed 70 ° for use in sand. Furthermore, the angle β ranges from 68 ° to 85 ° for use in soft clay and from 50 ° to 65 ° for use in sand. It is preferred that the angle β 30 does not exceed 80 ° for use in soft clay and does not exceed 60 ° for use in sand.

"Q DK 176364 B1 18

The shackle attachment point 26 (Fig. 11) is formed by an anterior end 28 of an elongated straight slot 29 in the shaft 2. A rear end 30 of the slot 29 is adjacent a rear edge 31 of the anchor tab 3, and the slot 29 forms a forward opening. angle γ of up to 30 ° with the center line 7, with 10 ° being preferred.

An anterior edge 32 of the shaft 2 is sharpened by bevel to reduce the resistance to penetration into the ground as well as at the edge 25 of the anchor tab 3. The separation of the shackle attachment point 26 from the geometric center of gravity C is preferably in the range of 0.15L to 0. 6L. A cylindrical steel pin 17 (Figs. 11-13) is mounted transversely through the shaft plate 2 to act as a pivot and bearing shaft 10 to fit with an installation follower 13 (Figs. 22, 23, 24).

The axis 33 of the pin 17 is at such a distance from the surface 24 that the axis 20 of the follower 13 passes through the united center of the area 34 (Fig. 12) of the anchor 23 and the shackle 5 (when the anchor rope 4 is retracted to lie parallel to the direction F) seen opposite to the direction F (Figs. 11, 12, 22). This ensures that the resulting resistance force R against penetration into the ground (Fig. 22) on the anchor 23 is colinear with the follower axis 20 during the initial driven embedding of the tug anchor 23. A releasable shackle stop 35 (Figs. 11, 14, 15, 16, 17) in the shaft 2 holds the pin 36 for the shank 5 at the end 28 of the slot 29. The stop 35 includes two rectangular plates 37 slidably disposed in lower recesses 20 38 on either side of the shaft 2 behind the end 28 of the slot 29 and on one side of the slot 29 which faces away from the anchor tab 3. The plates 37 initially begin with a position partly in the recesses 38 and partly in the slot 29, whereby the pin 36 of the shank 5 is prevented from sliding away from the end 28 of the slot. 29. A drilled hole 39 (Fig. 17) in the shaft 2 between the recesses 38 contains two steel balls 40 25 with a diameter slightly smaller than the diameter of the hole 39. The steel balls 40 are held apart by a compression spring 41. The plate 37 has a central hole 42 and an offset hole 43 drilled therein which engages with a ball 40 to determine the displaceable position of the plate 37 in the recess 38. The plate 37 also has an upwardly facing block 44 which is secured at an end that faces away from the offset hole 43, and extending 30 beyond the side surface 45 of the shaft 2 (FIG. 17). A cam 46 (Fig. 14) projecting within each eye 47 of the shank 5 is positioned so that sliding contact between the cam 46 and the block 44 occurs while the shank 5 is rotated from parallel to perpendicular to the surface 24 of the anchor tab 3. The lugs 46 thereby push on the blocks 44 to cause the plates 37 to depress the balls 40 out of engagement with the holes 43 and then slide until the balls 40 engage in the holes 42 holding the plates 37 completely free of slot 29 (Fig. 15). A non-rotatable non-rotatable sleeve 36A slidable in slot 29 may be mounted on pin 36 (FIG. 15) to prevent plates 37 from moving prematurely by friction between pin 36 and plates 37 when shaft 5 is rotated. around to bring the lugs 46 into contact with the blocks 44.

10

Subsequent pulls backwards in the anchor rope 4, the shank 5 rotates backwards until the lugs 46 release from the blocks 44 and thus allow the sleeve 36A and the pin 36 to slide along the slot 29 to be repositioned at the end 30 (Fig. 11), thereby retaining the anchor 23 at low load using the anchor rope 4 is possible.

Resetting of the stop 35 is later accomplished simply by using a hammer and acting on each of the plates 37 in turn to again bring the balls 40 into the apertured holes 43 and so as to bring the plates 37 back into the slot 29 again. to prevent the shank 5 from sliding away from the end 28 of the slot 29.

In accordance with a third embodiment of the present invention, a follower element (Figs. 18-25) for directly embedding a ship anchor beneath the surface 8 of a mooring base 10 comprises an elongated member 13 including a plurality of body segments 48. The segments 48 ( Figs. 19-21) have a width W and a square cross-section to provide tire stability. The segments 48 are axially symmetrical about an axis 20 with an axial passageway 49 provided therethrough to accommodate a chain 50 which is attached to a bottom end segment 51 of follower 13. The passage 49 is cross-sectional in order to limit the chain 50 rotationally relative to the segments 48.

30 20 DK 176364 B1

Segments 48 (Fig. 19) are each provided with a tapered stub 52 extending from a peripheral surface 53 at one end 54 of segment 48, and a corresponding tapered stub 55 recessed into a peripheral surface 56 at a opposite end 57, such that a projection 52 of 5 a segment 48 fits snugly into a recess 55 of an adjacent segment 48. Matching cylindrical surfaces 58 and 59 allow adjacent segments 48 to rotate while maintaining peripheral contact (FIG. 19-21). The axial passageway 49 in each segment 48 is expanded at each end to minimize axial bending of the chain 50 due to rotation between adjacent segments 48 as the follower 13 passes over a cylindrical stern roll 60 on a deck 61 of an anchor handling vessel 62 floating on the sea surface 63.

The chain 50 is attached to the lower end segment 51 (Fig. 30) by means of a pin 64 passing through an end link 65 of the chain 50 passed through each of the segments 48 (Figs. 18, 22-24) and through an upper body segment 66, 15 which acts as a control segment for holding and releasing tension in the chain 50.

The control segment 66 (Figs. 25-28) has an axial borehole 67 containing an elongated cylindrical mandrel 68 having an axial borehole 69 for receiving the chain 50 passing through it. A slotted cylindrical collar 70 is rigidly attached to three joints (Figs. 27-28) of the chain 50 to fit tightly within the length of the borehole 69 and is rotatably and axially secured therein by a securing pin 71 passing through the collar 70 and the wall 72 of the mandrel 68. The pin 71 is machined to be sheared at a load less than the breaking stress of the chain 50 to provide overload protection for the chain 50. The control segment 66 has slits 73 in opposite side faces 74 which re-enter. easy for the borehole 67. The mandrel 68 has opposed wedge blocks 75 which are bolted thereto and which engage and are slidable in the slots 73 and serve to retain the mandrel 68 pivotally with respect to the control segment 66. An internal threaded sleeve 76 is provided. external thread 77 engaging the wall 72 of the dome 68 so as to be axially adjustable and lockable thereto by a screwed locking ring 78 having a bevelled surface 79 facing away from the sleeve 76. The sleeve 76 has a peripheral groove 80 (FIG. 27-28) which receives a pair of opposed pawls 81 slidably mounted on an upper surface 82 of the control segment 66 and operable to project into the borehole 67 of compression springs 83 responding to tabs 84 extending upwardly from surface 5 82. Each pawl 81 has a lower inclined surface 85 (Figs. 27-28) for contact with the beveled surface 79 of the locking ring 78 and for displacing the pawl 81 against the spring 83 to allow passage of the locking ring 78 and thereafter. engagement of the pawl 81 in the groove 80 in the sleeve 76. The positions of the pawls 81 are guided by two arms 86 on a U-shaped yoke 87 (Figs. 25-26) slidably retained on the surface 82 of 10 stop tabs 88 extending face up from there. A compression spring 89 which reacts against a tab 90 extending upwardly from the surface 82 pushes the yoke 87 away from the tab 90 until the stop 91 of the arms 86 engages the stop tabs 88, whereby an outer edge 92 of the yoke 87 protrudes outside the edge 93 of the surface 82 (Fig. 26), unless it is aligned with the edge 93 upon contact with the stern roll 60 or deck 61 of the anchor handling vessel 62 (Fig. 18,26).

Each arm 86 of the yoke 87 has an inclined surface 94 (Figs. 25-26) which pushes on a correspondingly inclined surface 95 on each pallet 81 as the edge 92 of the yoke 87 is pressed in line with the edge 93 of the control segment 66 at contact with roll 60 20 or tire 61 (Fig. 18). This forces the pawl 81 to compress the spring 83 and move out of engagement with the groove 80 in the sleeve 76 (Fig. 28). The mandrel 68 is thus free to be displaced over a distance W / 4 along the borehole 67 to prevent unwanted extra tension from being applied to the chain 50 due to the follower 13 (Fig. 18) bending 90 ° on the transverse rear rollers 60.

25

The axial position of the sleeve 76 on the mandrel 68 is adjustable and can be locked by the ring 78 such that when the follower 13 hangs completely below the roller 60, the buoyancy weight of the follower 13 extends the chain 50 just enough to engage the pawls 81 with the groove 80 on the mandrel 68. This automatically prevents the stretch of the chain 50 from being quenched as the weight of the follower 13 advancing forward is supported during penetration into the seabed. Therefore, an ever-increasing clamping force occurs between the segments of follower 13 to provide rigidity which prevents the follower from deflecting before complete penetration.

Accordingly, the follower 13 functions substantially in the same manner as the aforementioned rigid follower, when suspended vertically by a rope 16, but permits recoverable bending without damage while passing over the stern roller 60.

An orientation joint 96 (Figs. 18, 29) having a cardioid comb 97 which abuts a straight edge 98 as disclosed in Applicant's UK Patent No. 5,197,107.

2 199 005 and U.S. Patent No. 4,864,955 are spaced from mandrel 68 in control segment 66. Chain 50 is connected via a pin 99 to a rear drawbar 100 on link 96, which drawbar is inclined below 45 ° to The link 96, in turn, is connected via a shackle 101 to the down lowering and salvage rope 16 laid out and hoisted by a first winch 102 on the deck 61 of the anchor handling vessel 62 (Fig. 18). The joint 96 can only lie over the roller 60 in a stable orientation when the straight edge 98 is in complete contact with the roller 60 and always revolves around the cardioid cam surface 97 until this one stable orientation is established. The link 96 is therefore used to force the joints of the chain 50 to be below 45 ° relative to the roller 60 in the only pivot orientation, which when transmitted to the control segment 66 via the collar 70 and the blocks 75 therein, the yoke 87 contacts the roller 60 , when the control segment 60 is raised therefrom.

25

The lower end segment 51 of the follower 13 is provided for releasably connecting to a tow anchor 23 as previously described and includes an elongated drawbar 103 (Figs. 22-23) to span the shaft 2 of the anchor 23 to allow a recessed socket 104 in each leg of the drawbar accommodates and fits 30 with the pivot 17 of the shaft 2. A tab 106 on each leg 105 of the puller has a hole 107 which is drilled therethrough and which is adjacent to a hole 108 in the shaft 2 23 DK 176364 B1 and receives a retaining locking pin 109 which holds the anchor 23 temporarily in the stretcher 103 of the lower end segment 51 with the forward direction F parallel to the axis 20 and the pin 17 suitably in the bases 104. A stop 21 of a leg 105 of the stretcher 103 restricts rotation of the anchor 23 around the pin 17 5 to a desired number of degrees by contacting the anchor tab 3. An anchor loss rope 4A of a length approximately 5% longer than the length of the pawl The link 13, is attached at one end to the shackle 5 of the anchor 23 and at another end to a hinge joint 110 for connection to the anchor rope 4. The hinge link 110 is provided with a protruding hinge pin 110A. Two parallel hooks 10,111 are spaced apart and mounted on the surface 74 of the control segment 66 which faces away from the yoke 87. Each hook 111 serves as a support for engagement with a protruding end of the hinge pin 110A, whereby the hinge link 110 can is detachably attached to the control segment 66 such that pulling upwardly in the anchor rope 4 at an angle less than 60 ° from the vertical 15 causes the hinge member 110 to engage the hooks 111. This removable connection allows the azimuth course of the anchor 23 to be controlled during installation by the anchor rope. 4 pulls the hooks 111 out of premature release of the shackle stop 35 and thus retains the possibility of disengaging the link 110 with the hooks 111 subsequently by lifting up the anchor rope 4.

20

For assembly in the port, all components of follower 13 and tow anchor 23 are laid out on deck 61 of anchor handling vessel 62 (FIG. 18) with the yoke 87 (FIG.

25-26) on the control segment 66 in contact with the tire 61. The tug anchor 23 is mounted on the lower end segment 51 with the pin 17 suitably in the bases 25 104 and the retaining lock pin 109 is mounted through the aligned holes 107 and 108. (Fig. 27) is attached to three joints of chain 50 at the required distance from a lower end of chain 50. The mandrel 68 is slid onto the collar 70 and secured thereto by the pin 71. The chain 50 is then pulled through the control segments 66 and segments 48 until the mandrel 68 contacts the farthest end of the borehole 67 (Fig. 27). The chain 50 now protrudes sufficiently from a segment 48 facing away from the cone segment 66 to enable the end portion 65 of the chain to be secured to the lower end segment 51 by the pin 64 (Fig. 30). A hydraulic chain jack is mounted on the control segment 66 to pull the chain 50 and subsequently compress the segments in the follower 13. The traction force in the chain 50 provided by the chain thrust is set equal to the submerged flow capacity of follower 13 and tow anchor 23 in association. This extends the chain 50 until the groove 80 (Fig. 27) in the sleeve 76 of the mandrel 68 is pulled opposite the pawls 81 of the control segment 66. The sleeve 76 is then rotated around the thread 77 and then locked by the ring 78 so that the pawls 81 can pass. in engagement with the groove 80, immediately before the load in the chain 50 is equal to the submerged flow capacity of follower 13 and tow anchor 23 in association. The chain jack is then removed and the orientation member 96 is secured between the rope 16 and the chain 50 at a distance from the mandrel 68 sufficient to allow the follower 13 to be pivotally free of the roller 60 as it hangs down there with the orientation member 96 in contact with the roller 60 (Fig. 29). The anchor loss rope 4A is connected to the shackle 5 of the anchor 23 and to the hinge link 110 which is then engaged on the hooks 111 of the control segment 66. This terminates the assembly of the anchor handling vessel 62. The anchor rope 4 is wound on a stake on an auxiliary anchor rope carrier prior to installation at sea.

20 At sea, the anchor handling vessel 62 and the anchor rope carrying vessel continue to the installation site. One end of the anchor rope 4 is conveyed to the vessel 62 for connection to the hinge joint 110 which engages the hooks 111 of the control segment 66 of the pile 13. The anchor rope 4 is then allowed to hang limply in a bow between the vessels to provide directional control of the pile. 13 and the anchor 23. On the vessel 62, towing game ropes are secured to the control segment 66 via rope washers secured in the vicinity of the stern roll 60 and actuated to pull the control segment 66 rearward on the deck 61 thus pushing the tug anchor 23 and the follower 13 overboard via the stern roller 60. the tie anchor 23 together with the bottom end segment 51 projecting outboard causes the follower 13 to bend through 90 ° over the roller 60. The resulting generation of excessive tension in the chain 50 is prevented by the mandrel 68 moving over a distance W / 4 axially along the borehole 67 within the control segment 66. The follower 13 thus bends through 90 °, co. as it passes across the roller 60, the tension in the chain 50 only increasing to a maximum value equal to the submerged float weight of the tug anchor 23 and the follower 13 in association. When a sufficient weight of segments 68 is overboard, follower 13 is automatically launched, braking restriction being provided by the game 102 when it finally expands rope 16 to lower follower 13 and tow anchor 23 down to surface 8 of mooring support 10 below. The anchor rope carrying vessel anchors 10 the rope 4 as the rope 16 is deployed by the anchor handling vessel 62 and maintains sufficient tension in the rope 4 to control the azimuthal alignment of the follower 13 and the anchor 23 until the anchor 23 is buried in the ground 10 of the seabed.

Tension produced in the chain 50 due to the submerged weight of the tow anchor 23 and the follower 13 extends the chain 50 and allows the groove 80 on the mandrel 68 to engage with the spring pawls 81 released by the spring-driven movement of the yoke. 87 when the control segment 66 is released from the roll 60. The pawls 81 prevent the chain 50 from containing and thus act to maintain the weight-induced tension in the chain 50.

20

The tow anchor 23 is pushed through the surface 8 of the mooring base into the ground 10 (Fig. 27) by the combined flow weight of the anchor 23 and follower 13 as the ropes 16 and 4 are laid out. Conveniently, rope 16 may include a heave compensator comprising, for example, an elastic nylon member to act as a stretchable absorber for heaving movement of the vessel 62 to facilitate smooth penetration into the surface 8 of the tow anchor 23. The segments of the follower 13 are clamped together by the tension. maintained in the chain 50 by the pawls 81 so that the follower 13 acts as if it were a stiff pile.

Completion of the penetration of the anchor 23 is signaled by a load cell on the game 102 of the anchor handling vessel 62 and indicated by the tension in the rope 16, which is reduced to the submerged weight of the rope 16 when the anchor 23 and follower 13 are fully supported by the ground in the rope 16. seabed. The rope 16 is then released to allow the vessel 62 to move free from the position of the follower 13. The anchor rope carrier now moves to a position directly above the follower 13 5 and pulls up into the anchor rope 4 so that the hinge joint 110 goes out of engagement with the hooks 111 on the follower 13 and the rope 4 become tight. A mark is formed on the tight rope 4, which is then retracted until the mark has moved through a distance approximately equal to the length of two segments 48 in follower 13. This raises anchor 23 and follower 13 together in ground 10 in the seabed and 10 simultaneously swing the anchor 23 around the pin 17 of the socket 104 (Figs. 22-23) to cause the securing pin 109 to split and press the anchor tab 3 to swing away from the vertical. The anchor rope 4 is then laid out to allow the submerged weight of the follower 13 to move the anchor 23 downward in the now tilted direction F of the anchor tab 3 (Fig. 23). When the rope 4 is raised upwards, an effective torque is formed between the submerged weight of the follower 13 and the tension in the anchor rope 4. When the rope 4 is subsequently deployed, an effective torque is formed between the submerged weight of the follower 13 and the now resilient earth resistance R acting on the anchor 23. Both moments act to increase the desired rotation of the anchor 23. This sequence is repeated several times. At each repeat, the anchor tab 3 of the anchor 23 is further rotated away from the vertical until the stop 21 contacts the anchor tab 3 (Fig. 23). This twisting process, also known as chilling, occurs without causing the geometric center of gravity C of the anchor tab 3 to decrease at penetration depth below the surface of the seabed 8 through a distance k as previously described for a direct embedding anchor 11 (Fig. 8). is loaded 25 after removing the installer 13.

The anchor rope 4 is now slackened to allow the anchor rope carrying vessel to move away to allow the anchor handling vessel 62 to re-position directly over the follower 13 so that the game 102 can pull the rope 16 in to haul the follower 13 up 30 from the anchor 23 from the mooring base 10 and up to the stern roll 60. When the control segment 66 comes into contact with the reel 60, the yoke 87 is pushed against the spring 89 and forces the pawls 81 against the springs 83 and out of engagement with the groove 80 in the mandrel 68. The mandrel 68 is thus released to move a distance approximately equal to W / 4 along borehole 67 to allow follower 13 to bend through 90 ° by moving up and over roller 60 without causing unwanted extra tension in the chain 50. Halting by the game 102 stops when the entire follower 13 is on the deck 61.

The vessel 62 then moves forward to pull the anchor rope 4 into the ground 10 (Fig. 24) at a suitable angle relative to the horizontal to the mooring of an object 10 to be held on the sea surface. The resulting movement of the shank 5 causes the lugs 46 (Figs. 14-16) of the sacking lug 47 to push the plates 37 of the stop 35 into the released position of the shaft 2 of the anchor 23 ready for easy later recovery of the anchor 23. Pulling of the anchor rope 4 away from the direction of the retained object then causes the shaft 5 to slide in the slot 29 to the end 30 (Fig. 11), 15 thereby providing low resistance to salvage of the anchor 23 during retrieval.

With respect to the directly embedded tow embed anchor 1 previously described, the directly embedded tow anchor 23 will follow a downwardly sloping 20 curved path 9 if it is loaded beyond the capacity it can provide at the measurement embedment depth. The anchor 23 will thus increase its capacity to accommodate the overload. Eventually, as with traditional tow embedding anchors, the tow anchor 23 will reach a limiting depth beneath the surface 8 of the mooring support 10 at which maximum capacity will be reached, but catastrophic failure will not occur as anchor movement is now horizontal and hence an normal safety factor of 1.5 for towing embedment anchors.

The anchor 23 and the follower 13 may advantageously be adapted to include the contents of the current applicant's pending international patent application no.

30 PCT / GB98 / 01089 (Publication No. WO98 / 49048), which describes a device for providing a film of lubricant on the outer surfaces of a ship anchor and a direct embedding follower. Referring to FIG. 30-33, a control segment 51 of follower 13 is attached to chain 50 as previously described. An upper portion 51A of segment 51 includes an axial cylindrical cavity 112 and an annular piston 113 attached to a piston rod 114. The annular piston 113 and piston rod 114 contain an elongated cylindrical cavity 115 which receives an elongated solid piston 116. An upper end of the plunger 116 is rigidly attached to the upper portion 51A of the segment 51 within the cavity 112.

The annular piston 113 is pivotally locked to the upper portion 51A by means of a wedge 117 which is displaceable in an inner groove 118 within the cavity wall 11 of the upper portion 51A.

lower end of the fixed piston 116. A removable locking cap 121 forms part of the segment 51 and serves, among other things, to hold the piston 113 within the cavity 112 and accommodate an annular seal 122 for sealing the piston rod 114. The segment 51 thus contains an upper annular cavity. 123 surrounding the piston 116 and a lower cylindrical cavity 115 within the piston rod 114.

the segment 51 allows a check valve 124 and a passage 125 to fill the cavity 123 with a suitable lubricant, and a check valve 126 and a passage 127 through the solid piston 116 allow the cavity 115 to fill with the lubricant, the piston rod 114 being maximally extended from the lock cap 121 .

20

The piston 113 has peripheral passages 128 parallel to the axis 20 which serve to guide lubricant past the piston 113 into the circumferential passage 129 of the locking cap 121. A plurality of holes 130 communicating with the passage 129 are uniformly distributed along the circumference of the the locking cap 121 to act as outer outlet openings for delivering lubricant uniformly to the outer surface of the locking cap 121. The piston rod 114 includes the drawbar 103, such as the hard drawbar 105 (Fig. 30). A passage 131 leads from the cavity 115 within the piston rod 114 and along each leg 105 to the pedestals 104 of the drawbar 103 so as to be adjacent and connected to a passage 132 located axially in the pin 17 of the anchor 23 when the pin 17 is inserted into the bases 104 of the drawbar 103 (FIG.

30). Ring gaskets 133 (Fig. 31) provide slidably releasable pivot 2g between the pin 17 and the drawbar 103 within the bases 104. A passage 134 (Figs. 30-32) extends within the shaft 2 of the anchor 23 of the passage 132 in the pin 17 of the passages 135 (Figs. 30, 33) extending parallel to and entering the sharp edge 32 of the shaft 2 and the sharp edge 25 of the anchor tab 3. Holes 136 are 5 distributed uniformly along the edges 25 and 32 so that providing outer outlet openings for the passageways 135 (Figs. 30, 33) to deliver lubricant uniformly to the outer surfaces of the shaft 2 and the anchor tab 3 of the anchor 23.

During use, the cavities 115 and 123 are filled with biodegradable vegetal grease grease lubricant 137 via the respective check valves 126 and 124. As the anchor 23 penetrates the surface 8 of the mooring base 10, as previously described, the soil forces the resistor R (Fig. 22). and 116 (FIG.

30) to pressurize lubricant 137 into cavities 115 and 123 and press lubricant along passages 128, 131, 132,134 and 135 and out of holes 130 15 and 136 as the anchor 23 and follower 13 are pressed into the ground 10 in the mooring substrate of their combined submerged weight. The isolation of the cavity 115 from the cavity 123 ensures that a desired dosage of lubricant volume delivered from the follower 13 relative to that delivered from the anchor 23 by a moving unit of the piston rod 114 can be obtained. soil 10, which passes over the outer surfaces of appellant 23 and follower 13, thus greatly reducing the ability of the soil to adhere to these surfaces. Therefore, the effective surface frictional forces on the outer surfaces of the anchor 23 and the follower 13 as a result of grounding are greatly reduced with the accompanying desired promotion of penetration into the mooring substrate 10 and very clearly subsequent promotion of low pick-up loads by salvaging the follower from the mooring substrate 10. When the follower 10 is brought out of engagement with the anchor 23, the supply of lubricant is interrupted. Subsequent movement of the anchor 23 along the web 9 strips off any remaining lubricant so that the frictional effects on the anchor 30 23 are restored, allowing it to act as a tug anchor as previously described.

30 DK 176364 B1

The anchor 23 may further be arranged to have an elongate plate element 138 (Fig. 34) in place of a shackle attached to the shaft 2 with an attachment hole 139 for the anchor rope at one end 140 and a drawbar 141 at another 5 end 142 gripping the shaft 2 and carrying a pin 36 for slidable and pivotal engagement in the straight slot 29. The shaft 2 has a curved surface 143 centered on the attachment point 26 at a front end 28 of the slot 29. A stop 144 within the drawbar 141 makes sliding contact with the surface 143, thereby holding the pin 36 at the point 26 until rotation of the element 138 about the 10 point 26 causes the direction of movement of the stop 144 to be parallel to the slot 29, the pin 36 being freely slid into the slot 29. rotary stop securing pin 145 is mounted in holes 146 in the drawbar 141 and in an adjacent holes 147 in the shaft 2 and serves to hold the elongated plate element 138 at a desired position on which the angle α is less than 95 ° and preferably less than 75 °. The fuse pin 145 is of such size that it is split when a certain load value at the hole 139 from the anchor rope 4 is exceeded. This allows the anchor 23 to initially act as a tow embedding anchor prior to splitting the lock pin 145 g thereafter to act as a tow anchor with greatly increased holding capacity as it is towed further.

20

A tug anchor 23 (Figs. 22-24) weighing 9 kg and a follower 13 weighing 126 kg were subjected to experiments on a slightly over-compressed seabed 10 of soft clay. All the mechanisms and procedures described earlier worked as planned.

With the geometric center of gravity C (Fig. 24) of the anchor 23 installed by means of the follower 13 to a depth below the surface 8 of the seafloor of three times the drag root of the area of the anchor tab 3, the anchor 23 provided a holding capacity of 53 times the anchor weight (immediately after salvage of follower 13 from the seabed 10) when the anchor rope 4 was pulled under a slope of 18 ° relative to the horizontal at the surface 8 of the seabed. Additional features caused the anchor 23 to drag 30 while being buried deeper to provide an ever-expanding holding capacity that eventually became constant at 189 times the anchor weight as the 31 C 17 geometric center of gravity C moved horizontally and with the anchor rope 4 inclined below 23 ° to horizontal. Experiments with and without lubricant 137 (fig.

30) showed that the lubricant increased penetration of the geometric center of gravity C of the anchor tab 3 by 3.2 times and showed that follower 13 should be at least 5 three times heavier without lubrication to achieve the same penetration that occurred with lubrication. In a non-lubricated experiment where the geometric center of gravity C of the anchor tab 3 of the anchor 23 was installed by means of the follower 13 to a depth below the surface 8 of the seabed at 1.1 times the square root of the area of the anchor tab 3, the anchor 23 provided a still decreasing holding capacity and moved back up to the surface 8 of the seabed as it was dragged from its install de position. These experiments demonstrated the efficiency of the lubricated installation by the follower of the tow anchor 23 and of avoiding the aforementioned Danforth boundaries at the angles α and β (Fig. 11) of the anchor 23.

The description contained herein provides certain embodiments of the present invention and the experiments set forth above show that the objects of the invention have been fulfilled. It will be appreciated that variations of these embodiments are within the scope of the invention. For example, a highly extensible synthetic rope may be used within the follower 13 instead of the chain 50, with the result that the voltage-relief mechanism in the control segment 66 may not be required.

Claims (16)

32 DK 176364 B1 Anchoring device comprising a ship anchor and anchor embedment means comprising an elongate follower member releasably attached to the anchor and 5 adapted to push the anchor into a mooring base, characterized in that the anchor (1, 11, 23) and the elongate follower (13) is adapted to provide a reaction pivot point (17) about which the anchor (1, 11, 23.) can pivot. Anchoring device according to claim 1, characterized in that a low-friction material layer is provided on the anchor embedding member (13). Anchoring device according to claim 1 or 2, characterized in that a material layer of a low friction material is provided on the anchor (1,11,23). 15 Anchoring device according to claim 1, characterized in that the ship anchor (1, 11, 23) is arranged to pivot around the pivot point (17) when a traction force is applied to the anchor by means of a fixed anchor rope (4). Anchoring device according to any one of the preceding claims, characterized in that the follower element (13) is arranged to bend irreversibly when subjected to transverse forces, for example as a result of passage over a curved surface, such as a stern roller. (60) on an anchor handling vessel (62) (Fig. 18). 25 Anchoring device according to claim 5, characterized in that the follower element (13) includes a lower end segment (51) which is attached to an immersion and salvage rope (50) and includes a plurality of body segments (48) supported by the lower end segment (51). 30 33 DK 176364 B1 Anchoring device according to claim 6, characterized in that the body segments (48) substantially surround the immersion and salvage rope (50). Anchoring device according to claim 6 or 7, characterized in that the segments (48) fit together by means of a convex projection (52) on one segment (48) which fits with a corresponding concave recess (55) in the adjacent segment (48). Anchoring device according to any one of claims 6-8, characterized in that the immersion and salvage ropes (50) form an axis through the body segments (48). Anchoring device according to any one of claims 6-9, characterized in that at least part of the rope (50) within the body segments (48) comprises at least either a panty or a chain. Anchoring device according to any one of claims 6-10, characterized in that when the rope (50) within the body segments (48) is extended under tension when the follower element (13) hangs vertically, said rope (50) is prevented from being extinguished. of a rope stop member (81) operating between an upper body segment (66) and the rope (50), whereby the body segments (48) are held in a state of axial compression which provides the elongate follower member (13) with a degree of transverse stiffness to to withstand deflection when the tracking element (13) is at least partially supported by contact with the surface of a seabed. 25 Anchoring device according to claim 11, characterized in that the rope stop (81) is releasable, whereby the rope (50), when the follower element (13) is pulled up and bent over a curved surface, is released within the follower element (13) to allow relative axial movement between the rope (50) and the upper body segment (66) 30 to avoid excessive stretching of the rope (50) due to bending of the follower element (13). DK 176364 B1 34 Anchoring device according to claim 12, characterized in that the rope stop (81) is releasable by movement of an actuator (87) which contacts the curved surface. 5 Anchoring device according to any one of claims 11-13, characterized in that the rope stop member (81) includes a tooth element located on one of the rope (50) and the upper body segment (66), which engages in a recess (80). ) in a recess (76) located on the other of the rope and the upper body segment (66). Anchoring device according to any one of the preceding claims, characterized in that the device includes means for supplying lubricating fluid for providing a layer of low friction fabric via channels to outer surfaces of at least the follower element (13) and the ship anchored. (1,11,23). A method of laying a tow embed anchor (1) or direct embed anchor (11) or tow anchor (23), comprising removably attaching an elongate follower (13) pivotally to the anchor (1, 11, 23) at a pivot point (17) and pushing the anchor down into a mooring base (10) by the guide member (13) substantially in a direction with a minimum projected area of the surface of an anchor tab member (3) of the anchor as viewed from a load supply point (26) for a fastener (5) ) for the anchor rope (4), which is attached to an anchor rope (4) until a geometrical center of gravity (C) of the anchor tab element (3) is at least twice the square root of the maximum projected area of the anchor tab element (3) below the surface of the the mooring base (10) and pulling in the anchor rope (4) before separating the follower element (13) from the embedded anchor (1, 11, 23) so as to cause the anchor tab element (3) to turn to an effect ground position in the mooring base (10) by pivotal reaction with the follower (13).