RUINEN, Roderick Michael (Hoflaan 55, RC Krimpen Aan Den Ijssel, NL-2926, NL)
VAN DEN ENDE, David Peter (Schenkeldijk 44, LN Zuid-Beijerland, NL-3284, NL)
RUINEN, Roderick Michael (Hoflaan 55, RC Krimpen Aan Den Ijssel, NL-2926, NL)
| Claims 1. Anchor comprising a fluke which can be introduced into an anchoring ground in accordance with a direction of penetration by exerting a pulling force on an anchor line connected to the anchor, and a measuring coupling which during introduction of the fluke forms part of a force transfer between the anchor line and the fluke, wherein the measuring coupling is provided with a first coupling member that is connected to the fluke, a second coupling member that is connected to the anchor line, a hollow coupling bar that couples the coupling members to one another, wherein the coupling members in the longitudinal direction of the coupling bar engage onto the coupling bar at different places in order to be able to deform it, and a measuring body extending through the hollow coupling bar and which at least at its outer ends is subjected to a deformation by the deforming coupling bar, wherein the measuring body is provided with deformation sensors for recording deformation parameters of the measuring body, wherein the measuring body has a central part that is situated all around and free from the inside of the hollow coupling bar, which central part has a substantially constant thickness of material, wherein local weakenings are present in the material of the central part, wherein the deformation sensors are placed in, on or near the local weakenings in order to record deformation parameters of deformation of the measuring body in, on or near the local weakenings. 2. Anchor according to claim 1, wherein the local weakenings in the material of the measuring body are formed by through-holes or recesses in the material of the measuring body. 3. Anchor according to any one of the preceding claims, wherein the measuring body comprises an elongated hollow straight cylinder. 4. Anchor according to any one of the preceding claims, wherein at least a part of the local weakenings is situated in a common plane transverse to a longitudinal axis of the measuring body, wherein the local weakenings in the common plane are distributed regularly around the axis. 5. Anchor according to any one of the preceding claims, wherein the deformation sensors are placed on the measuring body, in between two local weakenings . 6. Anchor according to any one of the preceding claims, wherein the measuring body comprises at least one elongated strip or plate . 7. Anchor according to any one of the preceding claims, wherein the measuring body comprises at least two elongated strips or plates which over their length are positioned substantially transverse to each other. 8. Anchor according to any one of the preceding claims, wherein the measuring body is fixedly connected to the coupling bar. 9. Anchor according to any one of the preceding claims, wherein the measuring body extends freely through the coupling bar between the outer ends connected to the coupling bar. 10. Anchor according to any one of the preceding claims, wherein the measuring body is narrower over its length between the outer ends than it is at its outer ends . 11. Anchor according to any one of the preceding claims, wherein the measuring body is made of metal, preferably of steel. 12. Anchor according to any one of the preceding claims, wherein the deformation sensors are grouped in at least one straight series extending substantially transverse to the longitudinal direction of the measuring body. 13. Anchor according to any one of the preceding claims, wherein the deformation sensors are grouped in several series distributed over the measuring body in the longitudinal direction of the measuring body. 1 . Anchor according to any one of the preceding claims, wherein the measuring coupling comprises two first coupling members that spaced apart from each other, engage onto the coupling bar. 15. Anchor according to any one of the preceding claims, wherein the measuring coupling comprises two second coupling members that spaced apart from each other, engage onto the coupling bar. 16. Anchor according to claim 14 or 15, wherein the two first coupling members or the two second coupling members within the measuring coupling form the outermost engagement onto the coupling bar. 17. Anchor according to any one of the preceding claims, comprising a shank that is fixedly connected to the fluke, wherein the first coupling member forms a part of the shank. 18. Anchor according to claim 17, wherein the first coupling member is situated at the outer end of the shank that faces away from the fluke. 19. Anchor according to claim 17 or 18, wherein the coupling bar, as regards rotation, is fixedly connected to the shank. 20. Anchor according to any one of the preceding claims, wherein the second coupling member forms the outer end of an anchor line coupling connected to the anchor line. 21. Anchor according to any one of the preceding claims, wherein the coupling bar in its longitudinal direction extends transverse to the longitudinal plane of symmetry of the anchor. 22. Anchor according to any one of the preceding claims, wherein the measuring coupling is provided with an inclinometer that is accommodated in the coupling bar. 23. Anchor according to claim 22, wherein the inclinometer is fixedly connected to the measuring body. 24. Anchor according to any one of the preceding claims, wherein the measuring coupling is provided with an accelerometer that is accommodated in the coupling bar. 25. Anchor according to claim 24, wherein the accelerometer is fixedly connected to the measuring body. 26. Anchor according to any one of the preceding claims, wherein the measuring coupling is provided with a pressure sensor for recording the water pressure at the location of the measuring coupling. 27. Anchor according to any one of the preceding claims, wherein the measuring coupling comprises an electronic circuit that is coupled to the deformation sensors, and preferably to the inclinometer and/or the accelerometer and/or the pressure sensor, wherein the electronic circuit is adapted for processing and transmitting measurement data therefrom to a remote calculation and processing unit. 28. Anchor according to claim 27, wherein the electronic circuit is fixedly connected to the measuring body. 29. Anchor comprising a fluke which can be introduced into an anchoring ground in accordance with a direction of penetration by exerting a pulling force on an anchor line connected to the anchor, and a measuring coupling which during introduction of the fluke forms part of a force transfer between the anchor line and the fluke, wherein the measuring coupling is provided with a first coupling member that is connected to the fluke, a second coupling member that is connected to the anchor line, a hollow coupling bar that couples the coupling members to one another, wherein the coupling members in the longitudinal direction of the coupling bar engage onto the coupling bar at different places in order to be able to deform it, and a measuring body extending through the hollow coupling bar and which at least at its outer ends is subjected to a deformation by the deforming coupling bar, wherein the measuring body is provided with deformation sensors for recording deformation parameters of the measuring body, wherein the measuring body has a cylindrical central part that is situated all around and free from the inside of the hollow coupling bar. 30. Anchor according to claim 29, wherein the central part is substantially hollow cylindrical. 31. Anchor according to claim 29 or 30, wherein the central part comprises at least 70% of the length of the measuring body, preferably at least 80%. 32. Anchor provided with one or more of the characterising measures described in the attached description and/or shown in the attached drawings. |
BACKGROUND OF THE INVENTION
The invention relates to an anchor, particularly for anchoring heavy maritime objects, such as a drilling platform, into an anchoring ground for a long period of use that may last many years.
Such anchors at an anchoring line are placed onto the anchoring ground from an installation ship, after which the installation ship pulls at the anchor line to bring the anchor into the anchoring ground. During pulling the pulling force on the anchor line is measured from the installation ship. The pulling force and the pulling path of the installation ship then form a parameter for the penetration path of the anchor and the expected holding force the anchor will be able to provide .
Owners of heavy maritime objects make high demands on the degree of reliability of the expected holding force. Therefore it has to be ruled out that a considerable component of the pulling force measured on the installation ship is for instance caused by obstacles that have engaged onto the anchor line during the insertion of the anchor.
International patent application WO 2010/041929 shows an anchor having a fluke and a shank that is positioned upright therefrom. By means of a hollow coupling bar the shank is coupled to the anchor line. Through the hollow coupling bar a measuring body extends that is provided with deformation sensors with which the deformation of the measuring body and as a result the hollow coupling bar can be measured. The deformation is a parameter for the action of forces between the anchor and anchor line. The object is obtaining an accurate parameter of said deformation.
SUMMARY OF THE INVENTION
According to a first aspect the invention provides an anchor comprising a fluke which can be introduced into an anchoring ground in accordance with a direction of penetration by exerting a pulling force on an anchor line connected to the anchor, and a measuring coupling which during introduction of the fluke forms part of a force transfer between the anchor line and the fluke, wherein the measuring coupling is provided with a first coupling member that is connected to the fluke, a second coupling member that is connected to the anchor line, a hollow coupling bar that couples the coupling members to one another, wherein the coupling members in the longitudinal direction of the coupling bar engage onto the coupling bar at different places in order to be able to deform it, and a measuring body extending through the hollow coupling bar and which at least at its outer ends is subjected to a deformation by the deforming coupling bar, wherein the measuring body is provided with deformation sensors for recording deformation parameters of the measuring body, wherein the measuring body has a central part that is situated all around and free from the inside of the hollow coupling bar, which central part has a substantially constant thickness of material, wherein local weakenings are present in the material of the central part, wherein the deformation sensors are placed in, on or near the local weakenings in order to record deformation parameters of deformation of the measuring body in, on or near the local weakenings.
The coupling bar deforms, particularly bends, depending on the forces exerted on the coupling bar by the first and second coupling member. The coupling bar in that case applies a bending onto the measuring body, wherein deformation of the measuring body is larger in, on or near the local weakenings that have been arranged therein, than at other locations of the measuring body. In that way the measuring body provides an accurate parameter of the deformation of the coupling bar, whereas the measuring body can be designed relatively slim so that it fits in a smaller cavity of a coupling bar. In case of the same outer dimension the coupling bar can thus be designed more solid. The deformation of the measuring body recorded by the deformation sensors is a parameter for the action of forces between the first and second coupling member as performed at the anchor side of the anchor line, that means independent of forces that may act on the anchor line by obstacles. In that way the expected holding force of the anchor can be predicted with a high degree of reliability. The relation between the action of forces and the deformations can be determined on the basis of interpolation of test data obtained earlier, or be calculated according to the rules of mechanics, for instance by means of a finite element analysis.
In one embodiment the local weakenings in the material of the measuring body are formed by through- holes or recesses in the material of the measuring body. In one embodiment the measuring body comprises a substantially rigid body in which the local weakenings have been arranged. Said weakenings can be arranged easily and accurately in the substantially rigid body, after its manufacturing. In one embodiment the rigid body consists of a single material, such as steel. In an easily manuf ctured embodiment the measuring body comprises an elongated cylinder, preferably a hollow straight cylinder.
In one embodiment at least a part of the local weakenings is situated in a common plane transverse to the longitudinal axis of the body, wherein the local weakenings in the plane are distributed regularly around the axis.
In one embodiment the deformation sensors are placed on the measuring body, in between two local weakenings . The deformation sensors thus have a large contact surface with a part of the measuring body where deformation will be largest relatively speaking, and therefore deform along in case of for instance bending of the measuring body.
In an alternative embodiment the deformation sensors are at least partially placed in and/or over a local weakening in the measuring body. When the weakenings comprise through-holes the deformation sensors are connected to the rest of the measuring body at the edge of the holes . In this embodiment the bending of the deformation sensors that are arranged in and/or over the through-hole is limited, whereas they can indeed stretch or shrink. When the weakenings comprise holes that are not continuous then the deformation sensors are preferably positioned such that they at least partially fill these holes that are not continuous. The freely situated central part of the measuring body on which the deformation sensors have been placed can thus be designed smooth to a large extent .
In one embodiment the measuring body is fixedly connected to the coupling bar, as a result of which deformations of the coupling bar can be transferred directly and proportionally onto the measuring body.
In one embodiment the measuring body extends freely through the coupling bar between the outer ends connected to the coupling bar, as a result of which the measuring body can easily be inserted in the cavity in the coupling bar. The cavity in the coupling bar may be defined by a straight bore through the coupling bar. In one embodiment the measuring body may then be narrower over its length between the outer ends than it is at its outer ends .
In one embodiment the measuring body comprises at least one elongated strip or plate. Due to its shape a strip or plate is suitable for mechanical calculations .
In one embodiment the measuring body comprises at least two elongated strips or plates which over their length are positioned substantially transverse to each other. The position transverse to each other offers the possibility to analyse the deformations according to a Cartesian coordinate system.
In a simple embodiment the strips are fixedly connected to one another.
In one embodiment the strips in cross-section form a cross . The deformation sensors can then be provided on all legs of the cross for an exact determination of the deformation of the coupling bar.
In one embodiment the measuring body is made of metal, preferably steel.
In one embodiment the deformation sensors are grouped in at least one straight series extending substantially transverse to the longitudinal direction of the measuring body. The deformation of the measuring body can then be recorded over a large part of its width including deformation differences over the length of the series, which renders an accurate determination of the deformation of the measuring body in its entirety and thus the coupling bar possible.
In one embodiment thereof the deformation sensors are grouped in several straight series distributed over the measuring body in the longitudinal direction of the measuring body, so that the deformation at several locations distributed over the length over a large part of the width of the measuring body can be recorded.
In one embodiment the measuring coupling comprises two first coupling members that spaced apart from each other, engage onto the coupling bar. The first coupling members connected to the fluke are able to load the coupling bar to bend in cooperation with the second coupling member, as a result of which the bending and its specific bending shape is a parameter for the force the anchor line exerts on the fluke, and for the direction of said force. Likewise the measuring coupling may comprise two second coupling members that spaced apart from each other, engage onto the coupling bar.
In one embodiment the two first coupling members or the two second coupling members within the measuring coupling form the outermost engagement onto the coupling bar. In between them the other or other coupling members can engage to load the coupling bar to bend.
In one embodiment the anchor comprises a shank that is fixedly connected to the fluke, wherein the first coupling member forms a part of the shank, wherein the first coupling member preferably is situated at the outer end of the shank that faces away from the fluke.
In one embodiment thereof the coupling bar, as regards rotation, is fixedly connected to the shank, as a result of which the direction of a force exerted on the coupling bar by the second coupling member can be related to the shank and the fluke.
In one embodiment the second coupling member forms the outer end of an anchor line coupling connected to the anchor line. The anchor line coupling may for instance be a bow shackle that can be swung about the coupling bar. The direction of penetration and thus the penetration forces will be substantially parallel to the longitudinal plane of symmetry of the anchor. In one embodiment the coupling bar in its longitudinal direction therefore extends transverse to the longitudinal plane of symmetry of the anchor, as a result of which the coupling bar extending transverse to the longitudinal plane of symmetry can be properly loaded to bend in order to determine the action of forces.
In one embodiment the measuring coupling is furthermore provided with an inclinometer that is accommodated in the coupling bar, so that in addition to the action of forces on the coupling bar also tiltings of the coupling bar with respect to a notional plane can be determined, which is a parameter for the pitch and roll of the anchor. In one embodiment the inclinometer is fixedly connected to the measuring body .
In one embodiment the measuring coupling is provided with an accelerometer that is accommodated in the coupling bar, so that by means of integration of the momentary acceleration in time the path of the coupling bar can be determined, which is a parameter for the penetration path of the anchor in the anchoring ground. In one embodiment the accelerometer is fixedly connected to the measuring body.
In one embodiment the measuring coupling is provided with a pressure sensor for recording the water pressure at the location of the measuring coupling. The water pressure is a parameter for the depth of the anchor with respect to the water line, from which the depth in the anchoring ground can be derived. In combination with for instance the pitch the horizontal component of the anchoring path may also be derived from the depth.
The data of the said measuring equipment can be processed and interpreted remote from the anchor, for instance from an installation ship, when the measuring coupling comprises an electronic circuit that is coupled to the deformation sensors, and preferably to the inclinometer and/or accelerometer and/or the pressure sensor, wherein the electronic circuit is adapted for processing and transmitting measurement data therefrom to a remote calculation and processing unit .
The inclinometer, the accelerometer and/or the electronic circuit may be placed in the hollow coupling bar as one prefab unit with the measuring body and be attached there when they are fixedly connected to the measuring body.
According to a second aspect the invention provides an anchor comprising a fluke which can be introduced into an anchoring ground in accordance with a direction of penetration by exerting a pulling force on an anchor line connected to the anchor, and a measuring coupling which during introduction of the fluke forms part of a force transfer between the anchor line and the fluke, wherein the measuring coupling is provided with a first coupling member that is connected to the fluke, a second coupling member that is connected to the anchor line, a hollow coupling bar that couples the coupling members to one another, wherein the coupling members in the longitudinal direction of the coupling bar engage onto the coupling bar at different places in order to be able to deform it, and a measuring body extending through the hollow coupling bar and which at least at its outer ends is subjected to a deformation by the deforming coupling bar, wherein the measuring body is provided with deformation sensors for recording deformation parameters of the measuring body, wherein the measuring body has a cylindrical central part that is situated all around and free from the inside of the coupling bar. Such a measuring body is easy to manufacture. In one embodiment the central part of the measuring body is substantially hollow cylindrical . Due to the cavity the cylinder offers less resistance to bending than would the case if it was designed solid. In the cavity of the cylinder further measuring equipment can be arranged.
In one embodiment the freely situated part comprises at least 70% of the length of the measuring body, preferably 80% or at least 80%. The freely situated part thus covers a large part of the measuring body that is thus able to bend free from the coupling bar. In one embodiment the measuring body is only attached or coupled with its outer ends to the coupling bar and/or its outer ends.
The aspects and measures described in this description and the claims of the application and/or shown in the drawings of this application may where possible also be used individually. Said individual aspects may be the subject of divisional patent applications relating thereto. This particularly applies to the measures and aspects that are described per se in the sub claims.
SHORT DESCRIPTION OF THE DRAWINGS
The invention will be elucidated on the basis of a number of exemplary embodiments shown in the attached drawings, in which:
Figure 1 shows an isometric front view of an anchor according to the invention, connected to an anchor line by means of a measuring coupling;
Figure 2 shows a side view of the anchor according to figure 1, introduced into an anchoring ground;
Figures 3A-3C shows a longitudinal section, a cross-section and a detail of the measuring coupling according to figures 1 and 2; Figures 4A and 4B show an isometric view and a side view of a cylindrical measuring body as used in the measuring coupling according to the invention,-
Figures 5A-5C show examples of the action of forces on the measuring coupling according to the preceding figures, during the introduction of the anchor in the anchoring ground;
Figures 6A and 6B show an isometric view and a side view of an alternative embodiment of a measuring body having a cross-shaped cross-section.
DETAILED DESCRIPTION OF THE DRAWINGS Figures 1 and 2 show a steel anchor l according to an embodiment of the invention. The anchor 1 is intended for anchoring heavy maritime objects, such as a drilling platform that is not further shown, in an anchoring ground 2, for a long period of use that may last many years. The anchor 1 comprises a fluke 10 and a shank 30 which, with respect to the fluke 10, inclines obliquely forward and which, at its outer end, is provided with a measuring coupling 50 with which the anchor 1 is connected to an anchor line 4. The anchor 1 is substantially symmetrical with respect to its longitudinal plane of symmetry . The anchor l is formed for in a forward direction of penetration P being introduced into the anchoring ground 2 substantially parallel to the longitudinal plane of symmetry M.
The fluke 10 is built up using plate members, and at its rear side comprises a base plate 11 over its width, which base plate on both sides of the centre longitudinal plane M merges into two triangular front ends 12. On both sides of the base 11 two downwardly oriented side plates 13 are provided which extend parallel to each other, and below the front ends 12 two parallel longitudinal girders 15 extend from the tips 14. At the upper side the fluke 10 is provided with upright securing lips 16, 17 having securing pins 18, 19 for the shank 30.
The shank 30 is built up with two plate-shaped shank legs 31 which in upward direction taper obliquely towards each other. The shank legs 31 are connected to each other along their length by means of transverse plates 34. At their lower side, the shank legs 31 have a bent portion 37 which is accommodated between the securing lips 16, 17, wherein the securing pins 18, 19 extend through fixing holes that are not shown in the bent portions 37. At the rear side the fixing holes are formed in a reinforced part 32 on the bent portion 37, which reinforced part 32 is provided with a series of extra holes 33 for adjusting the angle between the fluke 10 and the shank 30. At the upper end, the shank legs 31 are provided with end ears 35 extending parallel to each other and having fixing holes 36 for a measuring coupling 50 to the anchor line 4.
In the anchor 1 described, the coupling bar 54 forms the coupling between the bow shackle 51 and the fluke 10. Alternatively the coupling bar 54 takes the place of one of the pins 18, 19 with which the shank 30 is coupled to the fluke 10.
The anchor 1 described is provided with a fluke 10 and a shank 30 that is fixedly connected thereto and which ensures the connection between the fluke 10 and the anchor line 4. Alternatively the fluke 10 may by means of the securing lips 16, 17 be connected to pulling cables which come together at the location of the measuring coupling 50.
The measuring coupling 50 comprises a straight, cylindrical steel coupling bar 54 which extends through the fixing holes 36 of the end ears 35. The longitudinal axis or centre line S of the coupling bar 54 is oriented substantially perpendicular to the longitudinal plane of symmetry M. Between the end ears 35 the coupling bar 54 also extends through the eyes 52 of the bow shackle 51 coupled to the anchor line 4. The coupling bar 54 is accommodated under positive tolerances in the fixing holes 36 and the eyes 52, wherein an indexation that is not further shown is provided and which counteracts rotation of the coupling bar 54 about its centre line S with respect to the shank 30. The bow shackle 51 is able to swing about the coupling bar 54 in the longitudinal plane of symmetry M.
Figures 3A-3C show the measuring coupling 50 in more detail. The coupling bar 54 is provided with a cylindrical bore or inner space 55 which at the outer ends is closed off with end caps 56 which are welded together all round by means of a weld 57, as a result of which the inner space 55 is closed off watertight. In the inner space 55 an elongated measuring body 60 is confined which is shown in more detail in figures 4A and 4B. The cylindrical hollow measuring body 60 comprises an elongated cylindrical central part 67 and at its outer ends two broader cylindrical end parts 68. The end parts 68 each comprises a head end surface 65 and a longitudinal end wall 63, that abut the end caps 56, and the inside or bounding wall 58, respectively, of the inner space 55, wherein the head end surfaces 65 and/or longitudinal end walls 63 fittingly abut or are connected to the coupling bar 54. The central part 67 of the measuring body 60 has the shape of a straight hollow cylinder having a circle-cylindrical cross- section that is situated all round and free from the inside 58 of the hollow coupling bar 54. At the outer ends an elastic deformation of the coupling bar 54 is applied to the measuring body 60, particularly to the central part 67 of the measuring body 60 which part is situated free from the inner part 55 of the hollow coupling bar 54. In the central part 67 local weakenings are arranged in the form of through-holes 101, 102, 105, 106 in the material. The freely situated central part 67 has a substantially constant thickness of material transverse to the centre line S. Although not all holes are visible in the figures the measuring body 60 is provided with two groups of each four holes extending in the longitudinal direction of the measuring body 60, wherein the holes of each group are distributed evenly around the centre line S of the measuring body, with their centres situated on a notional perpendicular cross that is transverse to the centre line S.
On the measuring body 60, carrier strips 71,
72, 75, 76 are arranged between the holes 101, 102, 105, 106, which carrier strips are provided with deformation sensors, in this case electric strain gauges 80. The strain gauges 80 have been placed in order to record deformation near the through-holes 101, 102, 105, 106 arranged in the material of the central part 67. The elastic deformation of the measuring body 60 can be perceived best between the through-holes 101, 102, 105, 106 as around and near these holes there is locally less material to absorb elastic deformation. In this example a total of eight carrier strips 71-78 extending around the centre line S are arranged on the cylindrical hollow measuring body 60, on both sides of the centre parting thereof and on both sides of the longitudinal plane of symmetry M. Each carrier strip 71-78 is provided with a series of four electric strain gauges 80. In the embodiment of figures 4A and 4B the carrier strips 71-78 are each time arranged at equal distance between two holes 101, 102 that extend parallel to the centre line S in order to record the deformation in said area of the measuring body 60.
Although not shown here, in an alternative embodiment the carrier strips may partially span the local weakenings.
The measuring coupling 50 is also provided with a unit 82 having electronic inclinometers and accelerometers that are electrically connected to the printed circuit-board 81. The printed circuit-board 81 is furthermore connected to a partially external pressure sensor 90 for measuring the water pressure. The printed circuit-board 81 is furthermore connected to a power cable 83 which by means of a pull relief 84 is inserted in the coupling bar 54 and which is connected to a battery housing that is not further shown on the shank 30. The printed circuit-board 81 is furthermore connected to a communication cable 85 which by means of a pull relief 86 is inserted into the end cap 56 and which is connected to an acoustic modem 87 that is known per se for acoustic transfer 88 of data under water. Said pull relief 86 is shielded by means of a case 89 that has been welded thereon. The electronic circuit on the printed circuit-board 81 is adapted for receiving, processing and transmitting electric signals from the strain gauges 80, the inclinometers, the accelerometers and the pressure sensor 90. Due to the fixed orientation of the measuring body 60 with respect to the shank 30 the position of the anchor 1 with respect to a notional horizontal plane H and a notional vertical plane V can be determined, and thus the pitch and roll of the anchor 1. By means of the pressure sensor 90 the height of the water column above the coupling bar 54 and thus the depth of the anchor 1 with respect to the water line can be determined.
Figure 2 shows the anchor 1 during introduction in a submarine 3 anchoring ground 2 , such as a seabed, from an installation ship located on the water line 5 and which is not further shown. The installation ship is provided with an acoustic modem that is not further shown for communication with the modem 87 at the anchor 1, which modem is coupled to a calculation and data processing unit. In a preceding step the anchor 1 has been placed from the installation ship on the anchoring ground 2 at depth D, with the tips 14 of the fluke 10 in the direction of the installation ship. The acoustic modem 87 and the communication cable 85 are then still in the water 3. Subsequently the installation ship has exerted a force F on the anchor 1 via the anchor line 4, as a result of which the anchor 1 has gone through a penetration path J down to a certain depth E in the anchoring ground 2.
During going through the penetration path J the end ears 35 of the shank 30 on the one hand and the eyes 52 of the bow shackle 51 on the other hand have exerted bending forces and bending moments on the coupling bar 54, wherein the related deformations have been applied on the measuring body 60. This takes place within the elastic range of the coupling bar 54 and the measuring body 60. Subsequent thereto the strain gauges 80 have been subjected to deformations via the measuring body 60, for instance according to a distribution Q such as shown with vectors in figure 5C. The deformations of the individual strain gauges 80 on, in this case the cylindrical measuring body, and the data of the inclinometers and the accelerometers have been registered by the electronic circuit and directly communicated to the calculation and data processing unit on the installation ship. The calculation and data processing unit is able to derive the penetration path J from these data, and the related action of forces Fl- F3, as shown in figures 5A and 5B, between the anchor 1 and the anchor line 4, for instance by interpolation of known test data, or by a finite element analysis. The force may for instance be horizontally oriented as shown with force Fl, upwardly inclined at angles A, B as shown with force F2 or downwardly inclined at angles K, N. On the basis of the magnitude and the direction of the forces F1-F3 in relation to the penetration path J it can be determined with acceptable reliability whether the anchor 1 has set properly and whether it will be able to provide the specified holding force .
Figures 6A and 6B show an alternative measuring body 160 for use in a measuring coupling according to the invention. Said alternative measuring body 160 is built up with an elongated vertical steel plate 161 and a horizontal elongated steel plate 162 having a substantially constant thickness. In this example the steel plates 161, 162 are identical. The plates 161, 162 are both provided with two straight head end edges 165 which on both sides of the measuring body 160 via four straight longitudinal end edges 163 merge into two straight longitudinal side edges 164 that are receded therefrom and which form a narrowing of the respective plate 161, 162 with respect to the longitudinal end edges 163. The plates 161, 162 are both provided with a centre slot 166 which from one of the head end edges 165 extends over half the length of the respective plate 161, 162 after which the plates 161, 162 have been inserted in each others centre slot 166 and welded together over the full length. The measuring body 160 therefore has a substantially prismatic shape wherein the cross-section over the length is perpendicularly cross-shaped. When the measuring body 160 is placed in a hollow coupling bar 54, the straight longitudinal side edges 164 form a part that is situated free from the bounding wall 58 of the coupling bar 5 . Due to the said longitudinal weld the ribs of the cross are rigidly connected to each other. The plates 161, 162 of the measuring body are provided with local weakenings in the form of recesses 201-208 extending transverse to the longitudinal direction of the measuring body and debouching in the longitudinal side edges 16 . When the measuring body 160 is arranged in the hollow coupling bar 54 the measuring body 160 can be fixedly connected thereto, for instance by making a weld between the bounding wall 58 of the inner space 55 of the hollow coupling bar 54 and the longitudinal side edges 164. An elastic deformation of the coupling bar 54 is thus applied at the outer ends 168 of the measuring body 160, whereas it remains free from the bounding wall 58 over the narrowing defined by the longitudinal side edges 164. Figure 6B shows carrier strips 171-174 in more detail, which are provided with the strain gauges 80 and which are arranged near the recesses 201-204. Although not shown, at the rear side further carrier strips 175-178 are arranged. The carrier strips 171-178 and strain gauges 80 arranged thereon deform when the plates 161, 162 deform. Because of the local weakenings of the measuring body near the recesses 201-208 a bending force exerted on the measuring body 160 will particularly lead to deformation near those weakenings, so that also a relatively minor bending of the measuring body 160 can be clearly recorded. In an alternative embodiment that is not shown the carrier strips with the strain gauges thereon are placed partially over the recesses in order to span them.
The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert.
(OCtrooi/PCTP189124A des FG/NG 5149)