A releasable marine anchor

Abstract

A releasable marine anchor (1, 101, 201, 301, 401, 501, 601, 801) is disclosed which has a shank (3, 30, 203, 403, 503, 603, 803) having two ends. One end of the shank has an anchor line connected thereto and the other end of the shank has at least one seabed (25) engaging fluke (2, 102, 202, 302, 602. 802) pivotally connected thereto by an over centre toggle mechanism. The fluke(s) have an angle of attack relative to the shank which is changeable from an acute anchoring angle of attack to an obtuse release angle of attack by actuation of the over centre toggle mechanism by action of said anchor line acting on the shank.

Description

[0001] A RELEASABLE MARINE ANCHOR

[0002] Field of the Invention

[0003] The present invention relates to marine and riverine anchors and, in particular, to releasable marine anchors for small vessels, yachts and pleasure craft.

[0004] Background Art

[0005] Marine anchors have long been used to temporarily moor boats. Anchors with different arrangements of flukes, or seabed engaging portions, are known to cater for different types of seabed or riverbed. In particular, sand, gravel, mud, rock and coral call for different types of anchors.

[0006] It is common problem for anchors that they sometimes become unable to be disengaged with the seabed. This necessitates cutting of the anchor line and loss of the anchor, if the temporary moored boat is to be moved. Not only is this an economic loss, but the measure of safety provided to the boat by the anchor is thereafter no longer available to the boat until the (lost) anchor is replaced.

[0007] Genesis of the Invention

[0008] The Genesis of the present invention is a desire to address, and at least ameliorate, the above-mentioned problems by the provision of a releasable marine anchor.

[0009] Summary of the Invention

[0010] In accordance with a first aspect of the present invention there is disclosed a releasable marine anchor for temporarily mooring boats and like watercraft, said anchor comprising a shank having two ends, one end of said shank having connection means to connect an anchor line thereto and the other end of said shank having at least one seabed engaging fluke pivotally connected thereto by an over centre toggle mechanism, wherein said fluke(s) have an angle of attack relative to said shank which is releasable from an acute anchoring angle of attack to an obtuse release angle of attack by actuation of said over centre toggle mechanism by action of said anchor line acting on said shank. Preferably, the over centre toggle mechanism comprises first and second pivot axes supported by said other end of said shank, a third pivot axis located between said first and second axes, said at least one fluke being connected to, and being movable with, said third pivot axis to set said angle of attack between said fluke(s) and said shank, a first link having one end rotatably mounted on said first axis, a second link having one end rotatably mounted on said second axis, the other ends of said first and second links being pivoted to each other and being rotatably mounted on said third axis, and said first and second axes being resiliently movable towards and away from each other whereby said third axis is movable from one side to another of a line extending between said first and second axes to thereby change said angle of attack from acute in which said fluke(s) can engage said seabed, to obtuse in which said fluke(s) can be disengaged from said seabed.

[0011] In accordance with a second aspect of the present invention there is disclosed a method of releasing the fluke(s) of a releasable marine anchor.

[0012] Brief Description of the Drawings

[0013] Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0014] Fig. 1 is a perspective view from one side of the anchor of a first embodiment, Fig. 2 is a perspective view from the other side of the anchor of Fig. 1, Fig. 3 is a side elevation from the one side of the anchor of Fig. 1, Fig. 4 is a side elevation as in Fig. 3 but with the anchor inverted, Fig. 5 is an end view of the anchor of Fig. 1 looking towards the flukes, Fig. 6 is a plan view of the anchor of Fig. 1,

[0015] Fig. 7 is a side elevation of the links of the anchor of Fig. 1,

[0016] Figs. 8 -11 are a series of side elevations of the anchor of Fig. 1 illustrating how disengagement is achieved,

[0017] Fig. 12 is a perspective view of the anchor of Fig. 1 showing how the shank can be grasped to move the keeper,

[0018] Fig. 13 is a perspective view similar to Fig. 12 illustrating the movement of the keeper, Fig. 14 is a perspective view of the anchor of Fig. 1 illustrating the keeper in a first position,

[0019] Fig. 15 is an illustration similar to that of Fig. 14 but illustrating the keeper in a second position,

[0020] Fig. 16 is an illustration similar to that of Fig. 14 but illustrating the keeper in a third position,

[0021] Fig. 17 is a plan view of an anchor of a second embodiment,

[0022] Fig. 18 is a perspective view from the shaft end of the anchor of Fig. 17,

[0023] Fig. 19 is a perspective view from the rear end of the anchor of Fig. 17,

[0024] Fig. 20 is a perspective view similar to that of Fig. 18 but with half of the shaft omitted to show the interior workings,

[0025] Fig. 21 is a truncated perspective view of Fig. 20 but to an enlarged scale,

[0026] Fig. 22 is an exploded perspective view of a floating fluke axle arrangement of the anchor of Figs. 17-21,

[0027] Fig. 23 is an enlarged view of the axle of Fig. 22,

[0028] Fig. 24 is a perspective view from above of an anchor of a third embodiment,

[0029] Fig. 25 is a perspective view from below of the anchor of Fig. 24,

[0030] Fig. 26 is a perspective view of the anchor of Figs. 24 and 25 in the release configuration,

[0031] Fig. 27 is a first perspective view of an anchor of a fourth embodiment,

[0032] Fig. 28 is another perspective view of the anchor of Fig. 27,

[0033] Fig. 29 is a perspective view of an anchor of a fifth embodiment incorporating a buoyancy increasing device,

[0034] Fig. 30 is a perspective view of an anchor of a sixth embodiment incorporating a weighted rear end,

[0035] Fig. 31 is a perspective view from one end of an anchor of a seventh embodiment,

[0036] Fig. 32 is a perspective view from the other end of the anchor of Fig. 31,

[0037] Fig. 33 is an exploded perspective view illustrating the components which, when assembled, form the anchor of Figs. 31 and 32,

[0038] Fig. 34 is a perspective view of a tool of assistance in manipulating an anchor such as that illustrated in Figs. 31-33, Fig. 35 is a perspective view showing the tool of Fig. 34 engaged with the anchor,

[0039] Fig. 36 is a perspective view showing the shank of the anchor of Fig. 31 depressed thereby enabling the keeper to be manipulated,

[0040] Fig. 37 is a partial perspective view of a modified version of the anchor of Figs. 31-36 which includes a stop function which prevents the anchor releasing,

[0041] Fig. 38 is an exploded perspective view of the modified washer which achieves the stop function,

[0042] Fig. 39 is a partial perspective view similar to Fig. 37 but illustrating a different form which achieves the same stop function,

[0043] Fig. 40 is an exploded partial perspective view similar to that of Fig. 33 and illustrating the different washer form used in Fig. 39,

[0044] Fig. 41 is a side elevation of the arrangement of Fig. 39 with the flukes in a central position and the stop function playing no role,

[0045] Fig. 42 is a side elevation similar to Fig. 41 but illustrating the flukes stopped at a maximum deviation,

[0046] Fig. 43 is a perspective view of the entire anchor with the flukes in the position illustrated in Fig. 41,

[0047] Fig. 44 is a perspective view of the entire anchor with the flukes in the position illustrated in Fig. 42,

[0048] Fig. 45 is a perspective view of an anchor of an eighth embodiment having two lifters,

[0049] Fig. 46 is a different perspective view of the anchor of Fig. 45,

[0050] Fig. 47 is a close-up perspective view of the trailing end of the anchor of Fig. 45,

[0051] Fig. 48 is a perspective view from one side of one of the lifters of the anchor of Fig. 45,

[0052] Fig. 49 is a perspective view from the other side of the lifter of Fig. 48,

[0053] Fig. 50 is a side view of the anchor of Fig. 45 engaged with the seabed and provides a comparison with Fig. 8,

[0054] Figs. 51 and 52 are the same as Figs. 45 and 46 but show the anchor having a rode attachment ring,

[0055] Fig. 53 shows the anchor of Figs. 45-52 suspended by its rode attachment ring, Fig. 54 is a perspective view showing the anchor of Fig. 37 modified so as to have a stop function, and

[0056] Fig. 55 is a partial perspective view of Fig. 54 to an enlarged scale.

[0057] Detailed Description

[0058] As seen in Figs. 1-6, the anchor 1 of a first embodiment has a pair of pivoted flukes 2 located one to either side of a shank 3. The shank 3 has a pair of arms 5, 6 located one to either side of a bight 7. Slidingly located on the shank 3 is a keeper 9. The arm 5 includes three nuts or rings 11, 12, 13 welded to the arm 5 and with which the keeper 9 can engage.

[0059] As best seen in Fig. 2, the free end of the arm 5 terminates in a T-shaped arrangement which constitutes a first axle 15 which defines a first axis of rotation. A similar T- shaped arrangement at the free end of arm 6 similarly constitutes a second axle 16 which defines a second axis of rotation. In between the two axles 15, 16 is third axle 17 which defines a third axis of rotation.

[0060] A first link 21 has a first end 21 A pivoted on the axle 15 and a second end 2 IB pivoted on the third axle 17. Similarly, a second link 22 has a first end 22A pivoted on the axle 16 and a second end 22B pivoted on the third axle 17. The flukes 2 are rotatably mounted on the third axle 17 and are pivotably movable in an arc which is terminated by each fluke 2 coming into contact with either one of the axles 15, 16. Thus, the flukes 2 can have an intermediate position as illustrated in Fig. 3, and a more inclined position as illustrated in Fig. 4 in which the flukes 2 abut the lower one of the two axles 15, 16. It will be understood from Figs. 3 and 4 that the anchor 1 can come to lie either way up after it has been thrown overboard. Also, the anchor 1 may lie on either one of its sides, in which case the lower fluke 2 engages the seabed. Thus at least one of the flukes 2 is ready to engage the seabed irrespective of which way the dropped anchor 1 is initially orientated.

[0061] It will be appreciated that the arms 5, 6 and the bight 7 constitute a torsion spring so that the axles 15, 16 are spring-loaded and are capable of limited movement towards each other and away from each other. As illustrated in Fig. 7, the links 21, 22 normally have a V-shaped configuration which in Figs. 3, 4 and 7 points to the left. However, if the third axle 17 is moved to the right in Fig. 7 with sufficient force, then it is possible for the axles 15, 16 to be forced apart thereby enabling the links 21, 22 and axle 17 to flip over into a second V-shaped configuration illustrated in broken lines in Fig. 7 and which points to the right. As will be explained hereafter this action takes place if the release mechanism is to be activated.

[0062] In use, the anchor line or rode (not illustrated) is connected to the shank 3 and the anchor 1 is tossed overboard and ends up lying on the seabed normally in either the position illustrated in Fig. 3 with the arm 5 uppermost, or in the position illustrated in Fig. 4 with the arm 5 lowermost. Irrespective of which way the anchor 1 lies, gravity moves the flukes 2 downwardly as they pivot about the axle 17 so that the tips of the flukes 2 lie on the seabed (indicated by broken line 25 in Figs. 8-11). The anchor line pulls the shank 3 to the right as seen in Fig. 3 and so the flukes 2 dig into the seabed 25 which is the moored condition illustrated in Fig. 8. In the moored condition illustrated in Fig. 8, the forces of wind and tide exerted on the boat (not illustrated) move the shank 3 to the right and cause the flukes 2 to dig into the seabed 25. This action also urges the axle 17 to the left as seen in Fig. 8 thus urging the links 21, 22 into the configuration illustrated in Fig. 8.

[0063] In order to retrieve the anchor 1, as indicated in Fig. 9, the bight 7 is initially moved upwards as the anchor line is pulled into the boat. As this happens, if the flukes 2 come away from the seabed 25, then well and good and the anchor 1 can be pulled into the boat and the boat can proceed on its way. If, however, the flukes 2 remain engaged with the seabed 25, then the position is as illustrated in Fig. 9. In this position, the tips of flukes 2 are engaged with the seabed 25, the bases of the flukes 2 are engaged with the axle 16, and the bight 7 is being pulled upwardly so as to try and disengage the flukes 2 from the seabed 25.

[0064] If the flukes 2 do not disengage from the seabed 25, then eventually sufficient force is applied to the shank 3 by the anchor line becoming more vertical, to permit the arms 5, 6 to move sufficiently to permit the third axle 17 to flip over into the position illustrated in Fig. 10 (and illustrated by broken lines in Fig. 7). As a consequence of this flipped configuration, the angle of attack of the flukes 2 relative to the shaft 3 moves from an acute angle (preferably in the range of 25 - 60 degrees as illustrated in Figs. 4, 8 and 9) to an obtuse angle (preferably in the range of 100 - 145 degrees) as illustrated in Figs. 10 and 11. As a consequence of this change in the angle of attack, the flukes 2 are able to be disengaged from the seabed 25, thereby freeing the anchor 1 and allowing it to be hauled to the surface by the anchor line.

[0065] Once the anchor 1 is retrieved, as illustrated in Fig. 12, the shank 3 can be compressed thereby permitting the keeper 9 to be moved to the bight 7. This permits the axles 15, 16 to be easily moved away from each other and therefore the axle 17 to be moved away from the bight 7. As a consequence, the axle 17 can be easily moved between the axles 15, 16 so as to reset the flukes 2 into the acute angle of attack position. As illustrated in Fig. 13, the keeper 9 can be moved away from the bight 7 so as to complete the re-setting of the anchor 1. Normally if the anchor 1 is stowed then it adopts the configuration illustrated in Fig. 3 since it is lying on a hard surface.

[0066] Turning now to Figs. 14-16, the keeper 9 can be moved so as to lie between the nuts or rings 12 and 13 as illustrated in Fig. 14, or between the nuts or rings 11, 12 as illustrated in Fig. 15, or in front of the nut or ring 11 as illustrated in Fig. 16. These three positions each represent a different degree of stiffness with the position illustrated in Fig. 14 representing the least stiff condition and the position illustrated in Fig. 16 illustrating the “locked” position. As a consequence, in the position illustrated in Fig. 14, the anchor 1 is suitable for anchor retrieval with minimum effort. In the position illustrated in Fig. 15, the anchor 1 set for normal use. In the position illustrated in Fig. 16, the anchor 1 is set for maximum holding strength as would be indicated in the event of an approaching storm or cyclone (or typhoon or hurricane).

[0067] Turning now to Figs. 17-21, an anchor 101 of a second embodiment is illustrated in which like parts to the anchor 1 of Figs. 1-17 are indicated with a designation number increased by 100. Thus, the anchor 101 has flukes 102, for example. In the anchor 101 the pivoting of the flukes 102 is substantially similar to the pivoting of the flukes 2 of the anchor 1. However, the shank 3 of anchor 1 is completely changed in anchor 101 since its shank 30 comprises two side plates 31, 32 and includes an interior mechanism 33 which sets the break tension for the flukes 102. The shank 30 has a bight 107.

[0068] As best seen in Fig. 19, the flukes 102 are pivoted about a third axle 117 as before. The position of the third axle 117 is determined by the position of the first link 121 and the second link 122 which, as before, extend between a first axle 115 and a second axle 116. The third axle 117 also carries two U-shaped brackets 35 which tend to raise the rear of the anchor during initial engagement of the anchor with the seabed 25.

[0069] Turning now to Figs. 20 and 21, in both drawings the side plate 31 is omitted so as to reveal the interior mechanism 33. The axles 115 and 116 are respectively pivoted at the ends of two corresponding lever arms 41 and 42. Each of the lever arms 41 and 42 is pivoted about a corresponding rivet 44, 45 which extends between the side plates 31, 32. An orifaced plate 46 is secured between the side plates 31, 32 and carries a threaded bolt upon which two springs 48, 49 are positioned. A nut 50 holds the springs 48, 49 captive and sets the spring tension. The end of the bolt remote from the nut 50 carries an axle 52 upon which a pair of pivot arms 54, 55 are pivoted. The ends of the pivot arms 54, 55 are pivoted to the adjacent ends of the lever arms 41, 42 respectively.

[0070] As a consequence of this arrangement, the axles 115, 116 can be moved towards each other, or away from each other, so as to set the stiffness of the fluke release mechanism. This is brought about by rotation of the lever arms 41, 42 about the rivets 44, 45. The stiffness of this rotation is set by the degree of compression of the springs 48, 49 as determined by the position of the nut 50.

[0071] Turning now to Fig. 21, an over centre toggle lock mechanism 60 is provided by means of two link arm 61, 62 which pivot about corresponding rivets 63, 64 in the lever arms 41, 42. The link arms 61, 62 are joined together by means of a trigger bar 66 which passes through the link arms 61, 62 and is carried by two slots 67 (illustrated in Fig. 21) and 68 (illustrated in Fig. 18). If the trigger bar 66 is manually moved towards the nut 50, the link arms 61, 62 allow the lever arms 41, 42 to pivot about the rivets 44, 45. However, if the trigger bar 66 is manually moved away from the nut 50 then the link arms 61, 62 lock the lever arms 41, 42 and prevent their rotation. This in turn locks the flukes 102.

[0072] Fig. 22 is an exploded perspective view of the third axle 117 of Figs. 17-21 showing how the flukes 102 are each provided with a hollow square tube 118 which mates with a corresponding square portion 119 of the axle proper 117A. The axle proper 117A has a central cylindrical portion 120 which rotatably supports the links 121, 122. As best seen in Fig. 23, the axle proper 117A also includes two threaded portions 123 which each receive a corresponding retaining nut 124. By means of this arrangement, the angle of attack of both flukes 102 is constrained to be the same and is controlled by rotation of the axle proper 117A.

[0073] An advantage of the anchors 1, 101 is that the flukes 2, 102 by virtue of their shape and the resilience of the spring mounting of the axles 15, 16 and 115, 116 have a tendency to undertake a wavelike motion when moving through water or loose sediment. This motion is somewhat reminiscent of the wavelike motion of the torso of a person swimming the “Butterfly” stroke, or of the swimming motion of a porpoise. This wavelike motion makes it easier for the flukes 2, 102 to both engage with, and disengage from, seabeds having a loose consistency such as mud, sand, gravel and the like.

[0074] Turning now to Figs. 24-26, an anchor 201 of a third embodiment is illustrated in which like parts to the anchor 1 of Figs. 1-17 are indicated with a designation number increased by 200. Thus, the anchor 201 has a shank 203 having arms 205 and 206, for example. However, the anchor 201 has only a single fluke 202, reminiscent of a VULCAN Anchor by Rocna Anchors of New Zealand, for example and as disclosed in US Patent No 8,950,352 (Smith). The fluke 202 is joined to the shank 203 by means of a fin-like plate 204.

[0075] The arms 205 and 206 are formed from a strip spring steel of rectangular cross-section with a “landscape” orientation. This has the advantage that the bending moment of the shank 3 is increased so as to resist sideways motion applied to the shank 3 by the anchor line as a result of the boat swinging in an arc about the mooring. The arm 205 has a hollow cylinder at its free end which receives the axle 215. The free end of the arm 206 is bifurcated (as best seen in Fig. 26) and receives the second axle 216 which is located a small distance from the tip of the plate 204. At the tip of the plate 204 is the third axle 217. A first link 221 interconnects the first axle 215 and the third axle 217. A short length of the plate 204 which extends between the second axle 216 and the third axle 217, has an analogous function to that of the second link 22, 122.

[0076] A keeper 209 functions in the same way as the keeper 9 of Figs. 1-16. The heads of rivets 211, 212 and 213 are analogous in shape and function to the nuts or rings 11, 12 and 13 of Figs. 1-16. The anchor 201 in its release mechanism operates the same way as for the anchors 1 and 101. It will be seen in Figs. 24 and 25 that the third axle 217 is to the rear of the line joining the first and second axles 215, 216. However, as illustrated in Fig. 26, the shank 203 has moved rearwardly so as to place the first and second axles 215, 216 to the front of the third axle 217. As a result, the angle of attack of the fluke 202 relative to the shank 203 which is acute in Figs. 24 and 25, is obtuse in Fig. 26. Thus, in the configuration illustrated in Fig. 26 the anchor 201 can be released from the seabed even if initially fouled.

[0077] Turning now to Figs. 27 and 28, an anchor 301 of a fourth embodiment is illustrated in which like parts to the anchor 1 of Figs. 1-17 are indicated with a designation number increased by 300. Thus, the anchor 301, like the anchor 201 has only a single fluke 302, for example. Again, the fluke 302 is joined to the shank 303 by means of a fin-like plate 304. The shank 303 has arms 305 and 306 which are laser cut from a sheet of spring steel. The keeper 309 engages with three notches 311, 312, 313 which are formed on the arm 306 in this embodiment (rather than being formed on the arm 305). Again, the arm 306 is bifurcated and the arrangements of the axles 315, 316 and 317 is the same as for the axles 215, 216 and 217 of the anchor 201 of Figs. 24-26. The release mechanism of anchor 301 operates in the same way as the release mechanism of the anchor 201. Fig. 29 illustrates an anchor 401 of a fifth embodiment in which like parts to the anchor 301 of Figs. 27 - 28 are indicated with a designation number increased by 100. Thus, the shank 403 is the same as the shank 303, save that the arm 405 is provided with a buoyancy increasing device 469 which preferably takes the form of a rectangular strip of plastic, substantially water impermeable, foam material which displaces a significant amount of water but which does not weigh very much. The foam material 469 can be glued to the underside of the arm 405, for example. The intention of the foam material 469 is to place the centre of buoyancy of the anchor 401 above the centre of gravity of the anchor 401. As a consequence, when the anchor 401 is tossed overboard, the anchor experiences a righting torque which tends to turn the anchor 401 so as to place the arm 405 (with the foam material 469) uppermost. As a result, the probability of the anchor 401 landing on the seabed, such as seabed 25 of Figs. 8-11 for example, with the fluke 402 being below the shank 403 when the anchor 401 hits the seabed, is increased. As a consequence, the initial attitude of the anchor 401 when it hits the seabed is conducive to good engagement of the fluke 402 with the seabed.

[0078] Fig. 30 illustrates an anchor 501 of a sixth embodiment which is substantially the same as the anchor 1 of Figs. 1-16 with like parts to the anchor 1 of Figs. 1-16 being indicated with a designation number increased by 500. Thus, the shank 503 is the same as the shank 3. However, the rear of the anchor 501 is provided with a weight which preferably takes the form of a steel ball 570 which is joined to the rear of the anchor by a short length of chain 571. The function of the weight 570 is to reduce the chance of the anchor 501 skipping or hopping across seabeds having a hard surface. The additional weight of the weight 570 applies an increased downward force to the tips of the flukes 502 and therefore increases their interaction with the seabed.

[0079] Turning now to Figs. 31-33, an anchor 601 of a seventh 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. 22 and 23. 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.

[0080] As seen in Figs. 34-36, 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. 35, 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. 36.

[0081] A comparison of Figs. 35 and 36 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. 36, 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. 36. The advantage of the latch hook 714 is that the user can then use both hands in the manipulation of the keeper 609.

[0082] 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 bite angle is in the range of from 10° to 35° and preferably in the range of from 13° to 15°.

[0083] 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°.

[0084] 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.

[0085] 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. 37 and 38. As seen in Figs. 37 and 38, a modified spacer washer 637A is positioned between the pairs of link arms 621, 622. As best seen in Figs. 38, 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.

[0086] 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. 33. 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.

[0087] 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. 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.

[0088] An alternative stop mechanism is illustrated in Figs. 39-42. Here a modified spacer washer 637B is positioned on the axle 617 as illustrated in Fig. 40. 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.

[0089] As seen in Figs. 41 and 43, 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. 42, 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 mechanism functions to prevent the operation of the release mechanism.

[0090] It will also be apparent from Figs. 42 and 44 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.

[0091] 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.

[0092] 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,

[0093] 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,

[0094] 803 is desirable to enable the flukes to better bite into the hard ground.

[0095] 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. 54-55.

[0096] Turning now to Figs. 45-53, an anchor 801 of an eighth embodiment is illustrated in which like parts to the anchor 601 of Figs. 31-36 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. 50 as compared with Fig. 3 or 8.

[0097] 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 sea bed 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.

[0098] As best seen in Figs. 48 and 49, 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. 35 and 36, 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.

[0099] As seen in Figs. 51-53, 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.

[0100] Finally, turning now to Figs. 54 and 55, 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.

[0101] 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. 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 releasable marine anchor for temporarily mooring boats and like watercraft, said anchor comprising a shank having two ends, one end of said shank having connection means to connect an anchor line thereto and the other end of said shank having at least one seabed engaging fluke pivotally connected thereto by an over centre toggle mechanism, wherein said fluke(s) have an angle of attack relative to said shank which is releasable from an acute anchoring angle of attack to an obtuse release angle of attack by actuation of said over centre toggle mechanism by action of said anchor line acting on said shank.

2. The anchor as claimed in claim 1 wherein said over centre toggle mechanism comprises first and second pivot axes supported by said other end of said shank, a third pivot axis located between said first and second axes, said at least one fluke being connected to, and being movable with, said third pivot axis to set said angle of attack between said fluke(s) and said shank, a first link having one end rotatably mounted on said first axis, a second link having one end rotatably mounted on said second axis, the other ends of said first and second links being pivoted to each other and being rotatably mounted on said third axis, and said first and second axes being resiliently movable towards and away from each other whereby said third axis is movable from one side to another of a line extending between said first and second axes to thereby change said angle of attack from acute in which said fluke(s) can engage said seabed, to obtuse in which said fluke(s) can be disengaged from said seabed.

3. The anchor as claimed in claim 2 wherein said first, second and third axes comprise first, second and third axles.

4. The anchor as claimed in claim 3 wherein said fluke(s) are fixed to, and are rotatable with, said third axle.

5. The anchor as claimed in claim 4 wherein said shank is substantially U-shaped having two arms interconnected at one end, said first axis being located at the free end of one said arms, and said second axis being located at the free end ofthe other one of said arms.

6. The anchor as claimed in claim 5 wherein said shank having two arms comprises a torsion spring which provides said resilient movement of said first and second axes.

7. The anchor as claimed in claim 6 wherein a keeper limits the outward movement of said torsion spring arms.

8. The anchor as claimed in claim 7 wherein at least one of said torsion spring arms has a series of keeper locating protrusions or indentations to thereby define a plurality of positions in which said keeper is able to be positioned.

9. The anchor as claimed in any one of claims 1-8 and including a pair of overlapping lifters adjacent said shank other end.

10. The anchor as claimed in any one of claims 1-9 and including a stop mechanism to prevent said over centre toggle mechanism releasing.

11. The anchor as claimed in any one of claims 1-4 wherein said shank comprises a pair of substantially parallel plates which support a control mechanism for restraining movement of said axes.

12. The anchor as claimed in claim 11 wherein said control mechanism includes a pair of lever arms which are pivotally connected to said first and second axes to permit same to be moved towards, and away from, each other.

13. The anchor as claimed in claim 12 wherein each lever arm of said pair of lever arms is pivoted to a corresponding end of one of a pair of spring biased pivot arms.

14. The anchor as claimed in claim 13 wherein said lever arms includes a manually operable over centre toggle lock mechanism.

15. The anchor as claimed in claim 14 wherein said manually operable over centre toggle lock mechanism includes a trigger bar pivoted between a pair of pivotably mounted link arms.

16. The anchor as claimed in any one of claims 1-15 and having a pair of flukes.

17. The anchor as claimed in any one of claims 2-15 and having a single fluke interconnected with said shank via a plate extending from said fluke, a portion of said plate comprising said second link.

18. The anchor as claimed in claim 17 wherein said plate has a tip, said third axis extends through said tip, and said second axis extends through said plate at a location further from said tip than said third axis.

19. The anchor as claimed in any one of claims 1-18 wherein an additional weight is provided adjacent the other end of said shank.

20. The anchor as claimed in claim 19 wherein said additional weight comprises a metal ball and chain.

21. The anchor as claimed in any one of claims 1-20 wherein said shank includes a buoyancy increasing device to position its centre of buoyancy above its centre of gravity.

22. The anchor as claimed in claim 21 wherein said buoyancy increasing device comprises a mass of plastics foam which is substantially water impervious.

23. The anchor as claimed in any one of claims 1-22 in combination with an elongate hand tool for manipulating the over centre toggle mechanism; saidtool comprising an S -shaped curve at one end and a handle at the other end.

24. The combination as claimed in claim 23 wherein said handle includes a latch engageable with the shank of the anchor.

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