GB2183580A - Anchor - Google Patents

Abstract

A twin shanks 3 of an anchor present a tunnel passage 13 for gliding soil flow in an anti-lift attitude of its fluke 2 on a downward penetration course to a substantial burying depth for optimum holding power. The reinforced fluke has rear stabilisers 11 set at a negative angle of incidence to the ground and a front tip 8 at a positive angle thereto so as tip down the anchor on its penetration course. <IMAGE>

Description

SPECIFICATION An anchor Background of the invention This invention relates two an anchor comprising a reinforced fluke, and fixedly secured thereon a twin shank substantially of V-shape in end view.

In prior anchors ofthistypethetwin shank, dueto the disposition of its legs, resists the soil flow and hence the penetration of the anchor into the ground and is accordingly incapable to contribute to any appreciable extent to the burying capacity of the anchor.

Bearing in mind that besides factors such as its weightand fluke surface area, a mainfactorto determinethequalityofan anchoris its penetration or burying depth so that a deeply penetrating anchor will develop optimum holding power.

Summary of the invention In an anchor of the aforesaid type according to the present invention the twin shank is disposed so that optimum holdingforcewill bedeveloped,the arrangement being so that the twin shank legs are of plate or structural foil shape and disposed substantially parallel or slightly rearwardly diverging in sections parallel to the main body ofthe fluke whereby, when the anchor penetrates into the ground, the soil flow will glidingly pass through the so formed shank tunnel, the fluke having rear stabilizers which are at a slightly negative angle of incidenceto the ground, and/or a fronttip which is at a slightly positive angle of incidence to the ground so as to tip down the anchor on a steady penetration course to a great buried depth.

Accordingly, in the present anchorthe twin shank is capable to contribute largely to the burying capacityoftheanchorforoptimum holding power which may be as high as 100 to 200 times its own weightwhereasthusfar a holding power of 50times the anchorweight was considered exceptionally high.

Preferred is an embodiment of the present anchor wherebytherearstabilizerscomprisea pairof substantially delta-shaped ground slides, and whereby the front tip has front stabilizers formed by a digger adapter, to prevent both fore and aft and lateral canting, and for deep digging in a sliding motion.

Of further advantage is an embodimentwhereby the shank legs are mounted on a shank attachment box on fluke for adjustment atangles from 30 to with respect to the main body of the fluke for rock and soft ground, respectively, and whereby the fluke is dou bl e-wa I led with web reinforcement. Due to this sturdy and rigid construction the present anchor is of great strength and quite capable to withstand the extremely high holding force it develops, whereby auxiliaryflukes are mounted between the shank legs to tie said legs and to provide additional holding area.

In a preferred embodiment said auxiliary flukes are structural foils providing negative liftwhen penetrating intothe ground, whereby an auxiliary fluke between the shank legs attheshanktop is closed fore and aft below the anchorshackle eye so that the soil flow is streamlined through the tunnel passages and no clogging of soil will be experienced atthe V-top where the shank legs meet.In this respect the aforesaid slight rearward divergence of the shank legs, and also vertically between the auxiliary flukes, may be helpful to promote a smoother passage ofthe soil inviewofthefactthat soil particles when compressed have a tendency to break up in a greater number of smaller particles which occupy more space so that the soil then somewhatexpandswhich phenomenon is called dilatation of soil under compression.

To cut its way through the soil, and particularly through hard soil and even rocky ground, at least one precutter is provided on the tip and/or the lateral sides ofthefluke and/or on each ofthe shank legs for a saw-like action.

Afurther development according to the present invention resides in a provisionforan anchorwhich is to be heaved and also to be brought out by means of a hauling ring or strap called chaser, to be payed outto the anchor along the anchor line on a separate chaser line, and to be seized on the anchor.

The use ofsuch achaserwithachaserlinewould often be preferred above the use of the pennant as the pennant-line remains connected to the pennant-eye and is to be marked for its recovery by a buoy which constitutes an obstacle in the sea and should be beaconed to avoid collisions and infliction of damage, whereas the chaser and chaser line areto be brought out only when the anchor is to be heaved and accordingly constitutes no permanent obstacle in the sealane.

The chaser is brought out so far until it abuts on the ground-implementto be heaved and may, hence seized thereon, act then to pull the anchor loose, in a sense substantially opposite to the anchor line, and out ofthe ground in the same sense as this is done on the pennant.

But also when bringing outtheanchorthechaser can function.

It has appeared useful in said operations with a chaserthatthe anchor is to be orientated with its fluke tips in a predetermined desired sense and thereto, according to the present invention, the measure is taken that means are present to turn the anchor with the chaser resting on its abutment so thattheanchorwhen hauling iton board isto be turned with itsfluketips offthe shipto prevent damage, and to particularly also turn an anchor which would come to rest on the ground with its fluke tips directed upwardly, so that it can be pulled into the ground.

Said new measure consists in its preferred embodiment in thatthe anchor line-eye is formed in an arcuate member connected to the anchor shank and having an abutmentfora chaserwhich when it comes to rest on the abutment, when pulling on the chaser, turns the anchor 1800 about its axis and will seat in the arch of the arcuate member. For a proper turning action it would thereby be preferred that the arcuate member is integrated with the anchor line, or that the arcuate member is formed as a separate member,particularlyconfigured intheformofa harp shackle, which is to be connected with a second (harp shackle) eye provided at its end opposite to the anchor line-eye with a pin with an eye in the anchor shank, in which latter possible embodiment itwould be preferred that the arcuate member has formed on its backside at least one abutment cam whereon the chaser comes to rest.

It is observed that the herein presented provision could also be of use in other respects, particularly be kinematic reversal ofthe measure as provided.

With the use of a chaser also the chaserfixation has become of importance and as a further provision forthat purpose a device is arranged nearthe fairlead, comprising two pairs of catcher levers to catch the chaser at hinge pintles, one of said levers being longerthan the other of said levers so thatthe chaserwill be turned free ofthe chain at said hinge pintles. In its preferred embodiment said catchers are connected by a piece offlat.

The invention is explained in more detail inthe following specification in view of illustrative embodiments thereof as represented in the drawings, which should, however, not be interpreted in a restrictive sense.

Briefdescription ofthe drawings Figure lisa perspective view, in schematic outlines, of a twin shank anchor according to the present invention; Figure 2 is an elevation of a further embodiment of the present anchor; Figure 3 is a schematic drawing in plan view of the disclosed anchor; Figure 4schematically illustrates the operation of a chaser on an anchorwith a one-sided action, wherebythe abilityto orientate the anchor is particularly of importance; Figures 5a and 5b are schematic representatiosn of an anchor substantially depending on the anchor line and the chaser, respectively, and being turned;; Figure 6shows an anchor which has come to rest in reversed position in an undesirable manner, and which due to the new provision is to be turned by means of a chaser so as to be pulled with its fluke tips into the ground; Figure 7shows an anchor which is turned with the chaser, when bringing it on board, so as to prevent damage; Figures 8and 8a illustrate an arcuate anchor member according to the present invention,which is formed as a harp shackle; Figures 9 and 9a show a diagram ofthe forces acting thereon; Figures 10 and 10a show a shackle with pear eyes; and Figures 1 la-c showthe chaser fixation nearthe fairlead.

Description of the preferred embodiments As depicted in the drawing the anchor 1 has a fluke 2 and attached thereon atwin shank3.

The fluke 2 is a substantially delta-shaped hollow double-walled structure having top and bottom walls 4 and 5 jointed to form lateral sides 6 and 7 and afluketip8andreinforced bya bracingofwebss.

The rearend of the fluke 2 is truncated at 10 and the rearstabilizers are formed buy a pair of delta-shaped ground-slides 11.

The fluke tip 8 has a front stabilizer 12 attached thereto, preferablyintheform of a digger adapter as illustrated in the drawing.

The rear and front stabilizers 11 and 12 cooperates to keep the anchor 1 in a stable position on the ground on its fluke 2 which is so prevented from canting for and aft as well as laterally.

The front stabilizer 12 is of a forwardly and downwardly inclined configuration so as to present a positive angle of incidence to the ground, which in cooperation with the above described negative angle of incidence to the ground presented by the rear stabilizers provides a negative lift to tip down the fluke 2 that it is adapted to penetrate deep into the ground and promote the holding powerofthe anchor 1.

Theshank3 defines atunnel passage 13 between its legs 14which are substantially parallel or slightly rearwardly and upwardly diverging and are tied by preferablyfoil-shapedauxiliaryflukes 15whichare substantially parallel to or slightly rearwardly and upwardly diverging from the main bodyofthefluke2 so asto promote atunneled soil flowthroughthe twin shank 3 due to which the twin shank 3 will largely contribute to a deep penetration of the anchor 1 on a sliding downwardly bending course to a substantial buried depth for optimum holding power rated at 100-200 times the anchor weight.

As schematically illustrated the auxiliaryflukes 15 offoil-shape are adapted to provide a negative lift so asto further promote the deep penetration and high holding power ofthe present anchor.

It is noted that the above described slight rearward divergence of the shank legs 14 and auxiliaryflukes 15would promotethesmooth soil flowthroughthe tunnel passages 13 as soil particles, when compressed,haveatendencyto breakup in agreater number of smaller particles so that the soil would expand under compression which expansion is compensated for by the divergence of said passages 13 in the soil flow direction i.e. rearwardlyand upwardly.

The uppermost auxiliary fluke 15 attheshanktop is preferably forwardly and upwardly closed below the anchor shackle eye 1 6to streamline the flow into the uppermost tunnel passage 13 and prevent clogging in the V-corner 17 attheshanktop line 18 where the shank legs 14 meet.

As illustrated,theshank legs 14 are secured to a shank attachment box 19 which is erected on the fluke 2. The shank legs 14 are bolted to said box 19 and adjustable at angles from 30"to 50"for rockand soft ground, respectively. The rear side ofthis structure is radiused at 20 aboutthe main anchor shank bolt or king pin 21 as illustrated.

As a further provision the anchor 1 has at least one precutter2formed on its sides 6,7 and/or on its tip 8 and/oron each oftheshanklegs 14sothatitis adaptedto cut its way through the ground.

Afurther aspect of the newly invented anchor arrangement isforan anchor 101 as represented in Figures 4 and 5 having a one-sided action so that the hereafterdisclosed measureforturning it in the desired position is useful.

With the ever growing dimensions of offsnore operating drilling rigs also the mooring forces and hencetheanchorweights are considerably increased.

The result is that the anchor becomes very difficult to handlebytheworkshiporsupplyvesselserving such a drilling rig.

The demand for anchors with an ever increasing effectiveness is steady going on in the last decennia.

Recently an anchorwith one-sided action is introduced, which has increased the effectiveness with afactorofmorethanfourand handling instructionsofsuch an anchor have to befollowed carefully.

The anchors are stowed on board of the drilling rigs normally in anchor racks arranged alongside the rigs, with the fluke tips turned to inboard.

On board of the supply vessels the anchors are hauled on board by means of the pennant-wire, with the rearside leading, so that the fluke tips will not damage the vessel. With anchors acting on one side it is necessary, so as notto inflict damage, to turn the anchorwith its fluke tips outwardlywhen hauling it on board. This is also contrary to the requirement when bringing iton board a drilling rig,to rackthe anchor with itsfluketips inwardly directed.

As is ready set forth in the foregoing, particularly in deeper water, mostly chaser is being operated with, because the pennant-lines become too heavy and are ever more pronetogetdamaged.

In the drawing, the anchor is indicated at 101 and its fluke tips at 102 and the chaser is designated with 103 and the chaser line with 104. At 105 is indicated a drilling rig and at 106 a work or supply vessel serving the drilling rig 105.

To turn the anchor 101, when hauling it on board the workship 106, according to the present invention, use is made of a banana-shaped member 107 with a back cam 108 onto which the chaser 103 will abut, when lowered to the anchor 101 on the chaser line 104, so as to turn then the banana 107 and therewith the entire anchor 101. Upon turning the chaser 103 will seatthen in the inner arch 109 of the banana 107.

The principle is that due to the force Pappliedby the chaser 103 between the locationsAand Bas represented in Figure 9, the anchor implement is turned, which underthe anchorweightWthen works itselfwith its fluke tips 102 into the ground 110.

The course of action with the anchor 101 depending on the anchor line 111 and chaser line 104, respectively, is represented in Figures 5a and 5b.

Figure 8 shows in more detail the configuration of the banana or arcuate member 107 which, as also depicted in Figure 8, has a substantially semi-circular transverse section.

It is observed that the herein disclosed arcuate member 107 which has at its outer end 1 12the anchor line eye 113 therein, could also be fixedly connectedtotheanchorshankll4.

Furthermore links ll5intheformofpeareyes could be used, which are universally pivotal.

Reversely,this chaser device is also useful for turning an anchor in the ground when heaving it. The anchor shank could then be provided with abutments forthe chaser.

With the use of chasers also the fixation nearthe fairlead has become important. Originallythe chaser was simply hooked up art a knee fixed to the fairlead.

More and morethe chain was situated steeper than the original 45 degrees and it was impossibleto create a hook for the chaser. The chaser stayed in contact with the chain and when the chain was paid out or retrieved some meters, often the chaser was forgotten and damage was the result.

Figures 11 a-l 1c show a new device 1 16forfixation ofthe chaser 103 nearthe fairlead 117, which fixation device 116 comprises two pairs of catcher levers C, D to catch the chaser 1 03,when hauling it on the chaser line 104, atthe hinge pintles A, B. As lever C is longer than lever Dthe chaser 103 will be turned free ofthe chain 11 at said hinge pintles A, B. To limit the chaser movement a stopper E is mounted atthe fairlead 117.

The catchers C, Dare preferably connected by a piece of flat F.

Claims (18)

1. Ananchorcomprisinga reinforcedfluke(2), and fixedly secured thereon a twin shank (3) substantially of V-shape in end view, the arrangement being so thatthetwin shank legs (14) are of plate or structural foil shape and disposed substantially parallel or slightly rearwardly diverging in sections parallel to the main body ofthe fluke (2) whereby, when the anchor (1 ) penetrates into the ground, the soil flow will glidingly pass through the so formed shanktunnel (1 3),the fluke (2) having rearstabilizers (11 which are ata slightly negative angle of incidence to the ground, and/ora fronttip (8) which is at a slightly positive angle of incidence to the ground so as to tip down the anchor (1 ) on a steady penetration course to a great buried depth.

2. An anchoraccording to claim 1,wherebythe rear stabilizers comprise a pair of substantially delta-shaped ground slides (11).

3. An anchor according to claim 1 or2,whereby thefronttip (8) has front stabilizers (12) formed bya digger adapted.

4. An anchor according to any of the preceding claims, whereby the shank legs (14) are mounted on a shank attachment box (19) on theflukefor adjustment at angles from 30 to 50 with respect to the main body ofthefluke (2) for rockand soft ground, respectively.

5. An anchor according to any of the preceding claims whereby the fluke (2) is double-walled (4, 5) with web reinforcement (9).

6. An anchor according to any of the preceding claims, whereby auxiliary flukes (15) are mounted between the shank legs (14).

7. An anchor according to claims 6, whereby said auxiliary flukes (15) are structural foils providing negative lift when penetrating into the ground.

8. An anchor according to claim 7, whereby an auxiliary fluke (5) between the shank legs (14) at the shanktop is closed fore and aft below the anchor shackle eye (16).

9. An anchor according to any ofthe preceding claims, whereby at least one precutter (22) is provided on the tip (8) and/orthe lateral sides (6,7)of thefluke (2) and/or on each of the shank legs (14).

10. A provision for an anchor(101) which isto be heaved and also to be brought out by means of a hauling ring or strap called chaser (103), to be paid out to the anchor (101) along the anchor line (111) on a separate chaserline (104), and to be seized on the anchor (101), characterized in that means (107-109) are presentto turn the anchor (101) with the chaser (103) resting on its abutment(108).

11. A device according to claim 10, characterized in thatthe anchor line eye (113) is formed in an arcuate member(107) connected totheanchorsank (114) and having an abutment (108)fora chaser (103).

12. A device according to claim 11, characterized inthatthearcuate member(107) has a substantially semi-circulartransverse section.

13. Adevice according to claim 10 or 11, characterized in that the arcuate member (107) is integrated with the anchor shank (114).

14. Adeviceaccordingtoclaiml0orll, characterized in that the arcuate member (107) is formed as a separate member, particularly configured in the form of a harp shackle.

15. Adeviceaccordingtoanyoftheforegoing claims, characterized in that means in the form of a universally pivotal pear eye (115) are present.

16. A deviceforchaserfixation atthe fairlead, comprising two pairs of catcher levers (C, D) to catch thechaser(103) athinge pintles (A, B), one (C) of said levers being longer than the other (D) of said levers so that the chaser will be turned free of the chai n (111) at said hinge pintles.

17. A device according to claim 16,wherebysaid catchers (C, D) are connected by a piece of flat (F).

18. A device, substantially as represented in the specification and/ordrawing.