A variable angle of attack marine anchor

Abstract

A variable angle of attack marine anchor is disclosed having a shank with two ends and having a rode attachment means at one end and a pair of flukes at the other end. The flukes are pivoted about an axis located at the shaft other end and extend transverse to the shank. The flukes can pivot to either side of the shank up to a maximum angle of attack. A resilient means is located between the flukes and the shank to urge the flukes into a minimum angle of attack which the flukes adopt during initial contact with a seafloor.

Description

[0001] A VARIABLE ANGLE OF ATTACK MARINE ANCHOR

[0002] Field of the Invention

[0003] The present invention relates to marine and riverine anchors and, in particular, to such anchors having a pair of flukes.

[0004] Background Art

[0005] Many modem anchors having a pair of flukes are modelled on the Danforth anchor which has a pair of pivoted flukes located one to either side of a shank. Typically, the flukes can pivot about 10-15° to either side of the plane of the shank. Such anchors have a fixed maximum pivot so as to ensure that the fluke does not exceed the desired angle of attack of the fluke relative to the seabed when the anchor is initially installed.

[0006] However, it would be desirable to substantially increase the angle of attack of the flukes once they are initially embedded in the sea floor since to do so would substantially increase the holding power of the anchor. This particularly applies to anchors for larger vessels, such anchors having a weight in the range of from 500kg to 70 tonnes.

[0007] Genesis of the Invention

[0008] Accordingly, the Genesis of the present invention is a desire to enable the angle of attack of the flukes to be increased after the initial entry of the flukes into the sea floor.

[0009] Summary of the Invention

[0010] In accordance with a first aspect of the present invention there is disclosed a variable angle of attack anchor comprising a shank having two ends and having a rode attachment means at one end and a pair of flukes at the other end, said flukes being pivoted about an axis located at said shaft other end and extending transverse to said shank, wherein said flukes can pivot to either side of said shank up to a maximum angle of attack and a resilient means is located between said flukes and said shank to urge said flukes into a minimum angle of attack which said flukes adopt during initial contact with a seafloor. Brief Description of the Drawings

[0011] Several embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0012] Fig. 1 is a perspective view from the flukes end of an anchor of the first embodiment,

[0013] Fig. 2 is a perspective view from the rode end of the anchor of Fig. 1,

[0014] Fig. 3 is a side elevation of the anchor of Fig. 1 showing the flukes at a first inclined position relative to the shank,

[0015] Fig. 4 is a side elevation similar to Fig. 3 but showing the flukes in a second inclined position relative to the shank,

[0016] Fig. 5 is a side elevation of the shank without the flukes,

[0017] Fig. 6 is a perspective view from the flukes end of an anchor of a second embodiment,

[0018] Fig. 7 is a perspective view from the rode end of the anchor of Fig. 6,

[0019] Fig. 8 is a side elevation of the anchor of Fig. 6 showing the flukes at a first inclined position relative to the shank,

[0020] Fig. 9 is a side elevation similar to Fig. 8 but showing the flukes in a second inclined position relative to the shank,

[0021] Fig. 10 is a perspective view from the flukes end of an anchor of a third embodiment,

[0022] Fig. 11 is a perspective view from the rode end of the anchor of Fig. 10,

[0023] Fig. 12 is a side elevation of the anchor of Fig. 10 showing the flukes at a first inclined position relative to the shank,

[0024] Fig. 13 is a side elevation similar to Fig. 12 but showing the flukes in a second inclined position relative to the shank, and

[0025] Fig. 14 is a perspective view from the flukes end of the anchor of Fig. 10 with the flukes in the second inclination position.

[0026] Fig. 15 is a perspective view from one end of an anchor of a fourth embodiment,

[0027] Fig. 16 is a perspective view from the other end of the anchor of Fig. 15,

[0028] Fig. 17 is an exploded perspective view illustrating the components which, when assembled, form the anchor of Figs. 15 and 16,

[0029] Fig. 18 is a perspective view of a tool of assistance in manipulating an anchor such as that illustrated in Figs. 15-17, Fig. 19 is a perspective view showing the tool of Fig. 18 engaged with the anchor,

[0030] Fig. 20 is a perspective view showing the shank of the anchor of Fig. 15 depressed thereby enabling the keeper to be manipulated,

[0031] Fig. 21 is a partial perspective view of a modified version of the anchor of Figs. 15-20 which includes a stop function which prevents the anchor releasing,

[0032] Fig. 22 is an exploded perspective view of the modified washer which achieves the stop function,

[0033] Fig. 23 is a partial perspective view similar to Fig. 21 but illustrating a different form which achieves the same stop function,

[0034] Fig. 24 is an exploded partial perspective view similar to that of Fig. 17 and illustrating the different washer form used in Fig. 23,

[0035] Fig. 25 is a side elevation of the arrangement of Fig. 23 with the flukes in a central position and the stop function playing no role,

[0036] Fig. 26 is a side elevation similar to Fig. 25 but illustrating the flukes stopped at a maximum deviation,

[0037] Fig. 27 is a perspective view of the entire anchor with the flukes in the position illustrated in Fig. 25,

[0038] Fig. 28 is a perspective view of the entire anchor with the flukes in the position illustrated in Fig. 26,

[0039] Fig. 29 is a perspective view of an anchor of another embodiment having two lifters,

[0040] Fig. 30 is a different perspective view of the anchor of Fig. 29,

[0041] Fig. 31 is a close-up perspective view of the trailing end of the anchor of Fig. 29,

[0042] Fig. 32 is a perspective view from one side of one of the lifters of the anchor of Fig. 29,

[0043] Fig. 33 is a perspective view from the other side of the lifter of Fig. 32,

[0044] Fig. 34 is a side view of the anchor of Fig. 29 engaged with the seabed and provides a comparison with Fig. 8,

[0045] Figs. 35 and 36 are the same as Figs. 29 and 30 but show the anchor having a rode attachment ring,

[0046] Fig. 37 shows the anchor of Figs. 29-36 suspended by its rode attachment ring, Fig. 38 is a perspective view showing the anchor of Fig. 21 modified so as to have a stop function, and

[0047] Fig. 39 is a partial perspective view of Fig. 38 to an enlarged scale.

[0048] Detailed Description

[0049] As seen in Figs. 1-5, an anchor 10 has a shank 11 with an eyelet 12 at one end. The eyelet 12 forms a rode attachment mechanism. At the other end of the shank 11 is a pair of flukes 15, 16. The flukes 15, 16 are secured to, and pivot about an axle 17 which extends transversely relative to the shank 11. A pair of rivets 19 secure the flukes 15, 16 to the axle 17.

[0050] As best seen in Fig. 5, a collar 20 is slidably mounted on the shank 11 and extends between a first stop 21 and a second stop 22. A compression spring 24 is located on the shank 11 between a shank head 23 and the more distant stop 21. The collar 20 has a pair of oppositely directed lugs 26, 27. Each lug 26, 27 has a pair of first links 28, 29 pivoted thereto. The axle 17 has two pairs of second links 31, 32 pivoted thereto and located one to either side of the shank 11. The free ends of the first links 28, 29 and the free ends of the second links 31, 32 are pivoted together at one of two floating axles 34. The floating axles 34 extend transversely to the shank I l a distance sufficient to permit them to limit the maximum degree of rotation of the flukes 15, 16 about the axle 17. As a consequence of this arrangement, the first and second links form a parallelogram arrangement as best seen in Figs. 3 and 4.

[0051] When the anchor 10 is dropped to the seabed, gravity draws the flukes 15, 16 into the first inclined position illustrated in Fig. 3. In this position, the rode attached to the eyelet 12 drags the anchor 10 to the right as seen in Fig. 3 with the consequence that the tips of the flukes 15, 16 dig into the seabed (not illustrated). As a result, after this initial embedding, the seabed is able to exert a force on the flukes 15, 16 so as to rotate the flukes towards the second inclined position illustrated in Fig. 4. This rotation compresses the spring 24 which urges the flukes 15, 16 towards the first inclined position illustrated in Fig. 3. As a consequence, the above-described construction, when the anchor 10 is out of the water, the spring 24 causes the flukes 15, 16 to either lie substantially parallel to the shank 11, or lie within a narrow range bounded by the first inclined position illustrated in Fig. 3, typically 10-15° to either side of the shank 11. This sets the initial angle of attack of the flukes 15, 16. However, when the flukes 15, 16 are engaged with the seabed, the force of the anchored vessel pulling on the rode, and transmitted via the eyelet 12, is sufficient to compress the spring 24 so as to place the flukes in a more inclined position. With increasing force on the shank, the second inclined position illustrated in Fig. 4 is reached for a maximum anchor holding force.

[0052] Typically, the second inclined position is 25-40° to either side of the shank 11.

[0053] Clearly, when the anchor 10 is being retrieved after anchoring a vessel, the rode draws the eyelet 12 upwardly. If the flukes 15, 16 experience any resistance to extraction from the seabed, then the spring 24 can be compressed by pulling on the rode thereby allowing the shank 11 to pivot upwardly relative to the flukes 15, 16 and so aid in extraction of the flukes 15, 16 from the seabed.

[0054] Turning now to Figs. 6-9, an anchor 100 of a second embodiment is illustrated in which like parts to the anchor 10 of the first embodiment retain the same designation number. The shank 111 has the eyelet 12 at one end as before, but is fabricated from a pair of leaf springs 41, 42. The leaf springs 41, 42 are riveted together adjacent the eyelet 12 and have their free ends curled around the floating axles 34. The floating axles 34 are supported by the second links 31, 32 as before. An elongate double headed retainer 44 extends through an aperture 45 in each of the leaf springs 41, 42 and provides a stop mechanism which limits the movement of the leaf springs 41, 42 away from each other. As seen in Figs. 8 and 9, in the position illustrated in Fig. 8, the elongate rivet 44 does not restrict the leaf springs 41, 42 and thus the floating axles 34 limit the pivotable motion of the flukes 15, 16 into the first inclined position.

[0055] However, where the flukes 15, 16 experience an increased rotational force, then the flukes 15, 16 rotate towards the second inclined position illustrated in Fig. 9. In this position the elongate retainer 44 limits the movement of the leaf springs 41, 42 and thus limits the movement of the floating axles 34. Turning now to Figs. 10-14, an anchor 200 of a third embodiment is illustrated in which like parts to the anchor 10, 100 of the first and second embodiments retain the same designation number. A shank 211 has the eyelet 12 at one end as before, but is fabricated from a pair of flat strips 241, 242. The double headed elongate retainer 44 extends through the flat strips 241, 242 and again limits their movement away from each other. An expansion spring 224 extends between the floating axles 34 and urges them together so as to place the flukes 15, 16 in the first inclined position illustrated in Fig. 12. Rotational forces applied to the flukes 15, 16 urge the floating axles 34 away from each other, thereby expanding the expansion spring 224 until the limit provided by the elongate retainer 44 is reached. This places the flukes 15, 16 in the second inclined position illustrated in Fig. 13. This is also the position illustrated in Fig. 14.

[0056] Turning now to Figs. 15-17, an anchor 601 of a further embodiment is illustrated. The anchor 601 has a shank 603 cut from spring steel and having four bumps 611, 612, 613, 614 in each arm of the shank 603 which served to form location stops for a keeper 609. In addition, the first and second links 621 and 622 respectively are each formed from a pair of links located one to either side of the shank 603, thereby better balancing the forces involved. The arrangement is generally similar to that illustrated in Figs. 1 - 14. In particular, the two axles 615 and 616 are engaged with apertures at the free ends of the arms of the shank 603. Two spacer washes 635 and 636 are positioned between the shank 603 and the closer one of the two pairs of links 621, 622. The axle 617 passes through both of the centre pivots of the links 621, 622 and a spacer washer 637 maintains the desired separation between the two pairs of links 621, 622.

[0057] As seen in Figs. 18 - 20, a tool 708 fabricated by bending a steel rod, and preferably a stainless steel rod, is able to be used to manipulate the anchor 601. The tool 708 has a leading end 711 with an S-shaped curve 712. The tool has a trailing end 713 which functions as a handle and is preferably provided with a latch hook 714. As best seen in Fig. 19, the S-shaped curve 712 is inter-engaged with the axles 615 and 617. In this position, the trailing end 713 and the upper portion of the shank 603 can be grasped by a single hand of the user. The user then squeezes his hand so as to move the trailing end 713 towards the shank 603. This has the effect of moving the axle 615 towards the axle 616 using the axle 617 as a fulcrum, thereby compressing the two arms of the shank 603 against the natural resilience of the shank 603. This is the position illustrated in Fig. 20.

[0058] A comparison of Figs. 19 and 20 makes it apparent that the movement of the two arms of the shank 603 towards each other, frees the keeper 609 which is then able to be moved by the other hand of the user into the desired position relative to the bumps 611, 612, 613, 614 thereby setting the release force at which the over centre toggle mechanism of the anchor will be activated. If desired, as illustrated in Fig. 20, the latch hook 714 can be inter-engaged with the upper arm of the shank 603, thereby retaining the tool 708 in the position illustrated in Fig. 20. The advantage of the latch hook 714 is that the user can then use both hands in the manipulation of the keeper 609.

[0059] With the anchor of the above embodiments on a notionally horizontal seabed and a notionally horizontal anchor chain pulling on the shank, a bite angle exists between the seabed and the longitudinal axis of the flukes(s). For twin flukes the bite angle is in the range of from 10° to 35° below the horizontal, and preferably from 12° to 30°. For a single fluke, the bight angle is in the range of from 10° to 35° and preferably in the range of from 13° to 15°.

[0060] Just prior to the activation of the release mechanism, there is a pull angle between the longitudinal axis of the flukes(s) and the longitudinal axis of the shank which, for both twin flukes and single flukes, is approximately 70°.

[0061] Once the release mechanism has been activated, there is a release angle between the longitudinal axis of the fluke(s) and the longitudinal axis of the shank which is in the range of 100° to 130° and preferably in the range of from 105° to 120° for both types of fluke.

[0062] A stop mechanism is, in some circumstances, desirable to prevent the release mechanism from working. In particular, if heavy weather such as a cyclone, typhoon or hurricane is predicted, then it is very desirable that anchored vessels remain where they are anchored. One way of achieving this is illustrated in Figs. 21 and 22. As seen in Figs. 21 and 22, a modified spacer washer 637A is positioned between the pairs of link arms 621, 622. As best seen in Figs. 22, the modified spacer washer 637A is provided with two trailing arms 641, 642 each of which is provided with a through aperture 645. The two apertures 645 each receive a corresponding bolt 646 having a nut 647.

[0063] It will be apparent that without the bolts 646 and nuts 647, the modified spacer washer 637A functions in the same way as the washer 637 of Figs. 17. That is, it sits on the axle 617, maintains the spacing between the pairs of link arms 621, 622; and permits the axle 617 to move through the over centre position and thereby activate the over centre toggle mechanism.

[0064] However, where the two bolts 646 and the two nuts 647 are positioned within the apertures 645, then the axle 617 is only able to move through a limited distance before the bolts 646 and nuts 647 strike the link arm 621, 622. This stops the further motion of the axle 617 and therefore prevents the release mechanism from releasing.

[0065] If only one bolt 646 and its corresponding nut 647 are present in one of the apertures 645, then a different action is able to be achieved. The trailing arms 641, 642 are dimensioned to be long enough to permit the modified spacer washer 637A to rotate about the axle 617, thereby permitting the axle 617 to pass through the over centre position. That is, both bolts 646 and both nuts 647 are required to stop the release mechanism from operating.

[0066] An alternative stop mechanism is illustrated in Figs. 23-26. Here a modified spacer washer 637B is positioned on the axle 617 as illustrated in Fig. 24. The modified spacer washer 637 B is provided with a single trailing arm 650 again having a through aperture 645. An arcuate cap 651 is secured to the modified spacer washer 637B by means of a screw 652 which passes through the trailing arm 650 of the modified spacer washer 637B. As seen in Figs. 25 and 27, with the axle 617 in its position furthest away from the shank 603, there is no inter-engagement between the cap 651 and the link arms 621, 622. However, as seen in Fig. 26, as the axle 617 moves towards the shank 603, the cap 651 engages the link arms 621, 622 and prevents the axle 617 reaching the centre of the over centre toggle mechanism. As a consequence, the lock or stop mechanism functions to prevent the operation of the release mechanism.

[0067] It will also be apparent from Figs. 26 and 28 that with the cap 651 engaged with the link arms 621, 622 then the flukes 602 are able to achieve a maximum acute angle relative to the shank 603. This represents a maximum holding force of the anchor 601. It is particularly advantageous for the maximum holding force to be achieved in the configuration in which the stop mechanism prevents the release mechanism from functioning.

[0068] The stop or washer 637B and the stop or cap 651 both have a significant effect upon the performance of the keeper 609, 809. Without such a stop, the position of the keeper 609, 809 controls the tension at which the release mechanism functions (and in its position furthest away from the rode prevents the release mechanism from working). However, with such a stop, the position of the keeper 609, 809 controls the ease with which the flukes 602, 802 increase their angle of inclination relative to the shank 603, 803.

[0069] Thus, with the keeper 609, 809 moved towards the rode and away from the flukes 602, 802, the flukes will easily achieve a maximum inclination to the shank 603, 803. This setting is particularly advantageous in soft mud since it allows a maximum stopping power to be quickly achieved. However, with the keeper 609, 809 moved away from the rode and towards the flukes 602, 802 so it is harder for the flukes 602,

[0070] 802 to pivot away from the shank 603, 803. This setting is particularly advantageous in hard ground where a smaller angle between the flukes 602, 802 and the shank 603,

[0071] 803 is desirable to enable the flukes to better bite into the hard ground or seabed.

[0072] It will therefore be seen that limiting the movement of the axle 617, 817 converts the keeper 609, 809 from a tension setting device for a release mechanism to a mechanism to determine the ease with which the fluke angle relative to the shank 603, 803 is increased. The above discussion applies equally to the embodiment to be described in relation to Figs. 38-39.

[0073] Turning now to Figs. 29-37, an anchor 801 of yet another embodiment is illustrated in which like parts to the anchor 601 of Figs. 15-20 are indicated with a designation number increased by 200. Thus, the anchor 801 has flukes 802, for example. In the anchor 801 the pivoting of the flukes 802 is substantially similar to the pivoting of the flukes 602 of the anchor 601. However, the anchor 801 is provided with two lifters 881, 882 which are intended to elevate the trailing end of the anchor 801 above the seabed 25 as seen in Fig. 34.

[0074] This modification is desirable because it is necessary to increase the size and weight of the anchor in order to be able to successfully temporarily moor vessels of increasing length and hence displacement. As the size of the anchor increases, the size of the flukes 602, 802 also increases. The majority of the weight of the flukes 602, 802 is towards the tips of the flukes. As a consequence, when the anchor initially reaches the seabed 25, without the lifters 881, 882, the weight of the flukes 802 changes the angle of attack of the flukes 802 beyond what is desirable for a fast embedment into the seabed 25. The larger flukes 802 also tend to sit flatter on the seabed 25. However, with the lifters 881, 882 the angle of attack of the flukes 802 is increased relative to what would be the angle of attack without the lifters 881, 882. As a consequence, with the lifters 881, 882, the flukes 802 do not skate over a flat seabed surface such as hardpacked sand, but instead bite into the seabed surface and quickly set the anchor as desired.

[0075] As best seen in Figs. 32 and 33, each of the lifters 881, 882 have a cheek 883 and an arm 884. One of the cheeks 883 engages the seabed 25 and performs the lifting action. The arms 884 overlap and thus provide a protective ring which prevents an anchor chain, for example, fouling with the cheeks 883. In addition, each of the lifters 881, 882 has a hole 886 which enables the lifters 881, 882 to be mounted on the axles 815, 816 corresponding to the axles 615, 616 as seen in Figs. 19 and 20, for example. Thus, each of the lifters 881, 882 replaces a corresponding one of the two washers 635 and 636 between the axles 615, 616 and the shaft 603.

[0076] As seen in Figs. 35-37, the anchor 801 is preferably provided with a rode attachment ring 887 which engages the shaft 803. In addition, each of the arms of the shaft 803 is provided with an inwardly directed bump 810. As a consequence, as seen in Fig. 45, the ring 887 can be positioned between the bump 810 and the keeper 809. In this position, since the weight of the flukes 802 is towards the tips of the flukes, the ring 887 is substantially aligned with the centre of gravity of the anchor 801. Thus, the anchor 801 can balance from a chain as illustrated in Fig. 45. This balancing condition is particularly useful in the event that the tips of the flukes 802 pass under a rope or cable, for example, lying on the seabed. As a consequence, the entire anchor 802 can be moved rearwardly allowing the tips of the flukes 802 to be extracted from underneath such a rope or cable.

[0077] Finally, turning now to Figs. 38 and 39, the lifters 881, 882 can be modified so as to provide the above-mentioned stop function. This is done by casting a generally U- shaped lug 890 at the end of each of the arms 884. It will be appreciated that as the axle 817 moves towards the keeper 809 and thus approaches the centre of the over centre toggle mechanism, so the two lugs 890 abut each other and prevent further forward movement of the axle 817.

[0078] The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the marine anchor arts, can be made thereto without departing from the scope of the present invention. For example, the features and advantages disclosed in one facet of the invention may be utilised, mutatis mutandis, in other facets of the invention.

[0079] The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of’.

Claims

CLAIMS1. A variable angle of attack anchor comprising a shank having two ends and having a rode attachment means at one end and a pair of flukes at the other end, said flukes being pivoted about an axis located at said shaft other end and extending transverse to said shank, wherein said flukes can pivot to either side of said shank up to a maximum angle of attack and a resilient means is located between said flukes and said shank to urge said flukes into a minimum angle of attack which said flukes adopt during initial contact with a seafloor.

2. The anchor as claimed in claim 1 wherein a stop mechanism limits the range of pivotal movement of said flukes to said maximum angle of attack.

3. The anchor as claimed in claim 2 wherein said stop mechanism incorporates said resilient means whereby said flukes pivot under load to increase the range of said pivotal movement of said flukes towards said maximum angle of attack.

4. The anchor as claimed in claim 3 wherein said resilient stop means comprises a collar slidable along said shank between the two stops and a compression spring having one end abutting said shank and the other end abutting said collar and being compressible by movement of said collar.

5. The anchor as claimed in claim 4 wherein said collar is retained on said shank by a pivotable linkage arrangement extending between said collar and said shank.

6. The anchor as claimed in claim 3 wherein said resilient stop means comprises a bifurcated resilient shank having two arms with a double -headed retainer extending between said arms and limiting distance between said arms.

7. The anchor as claimed in claim 6 wherein each of said arms has an aperture through which said retainer passes.

8. The anchor as claimed in claim 3 wherein said resilient stop means comprises a bifurcated shank having two arms, each arm having a free end which is connected to a corresponding floating axle, and an expansion spring extending between said floating axles to limit the distance between said arms.

9. The anchor as claimed in any one of claims 1-8 wherein said resilient means comprises an over centre toggle mechanism.

10. The anchor as claimed in claim 1 wherein said resilient means can release said maximum angle of attack from an acute angle to an obtuse angle.

11. The anchor as claimed in claim 1 wherein said resilient means loads the pivotal movement of said shank relative to said flukes.

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