GB2035242A - Anchor - Google Patents

Abstract

A marine anchor has an L-shaped shank with a single fluke 10 fixed symmetrically at the end of the shorter leg. The fluke has three flat undersurfaces constituting a sole and two lateral upwardly inclined lugs 15. The fluke leading edges are swept back and are preferably slotted to define pairs of toes 21. The length to width ratio of the fluke is unity or less. The anchor is effective for a wide range of mooring bed conditions, is self-burying, and can be fabricated readily from steel plate. The invention is applicable to all sizes of anchors.

Description

SPECIFICATION Anchor This invention relates to anchors for mooring boats, ships, floating structures and the like.

The invention is particularly concerned with such anchors having a single fluke fixed with respect to a shank.

In this description and in the appended claims, the term "fluke" refers to that part of the anchor adapted and arranged on the shank for penetrating engagementwith a mooring bed of penetrable material such as mud, sand, shingle and the like thereby to develop resistance to being dragged. Drag forces are transmitted to the fluke by way of the shank the free end portion of which is adapted for connection to an anchor line, chain, cable or rope.

According to one aspect of the present invention, there is provided an anchor having a single fluke fixed with respect to a shank of generally L-shape, the fluke being disposed atthe end of one leg of the shank symmetrically with respect to the medial plane of the shank, and the underside of the fluke comprising three flat surfaces lying respectively in mutually different planes each of which intersects the others along lines parallel with or in the medial plane of the shank.

Further, according to a second aspect of the present invention, there is provided an anchor having a single fluke fixed with respect to a shank, the fluke being disposed at one end of the shank symmetrically with respect to a medial plane of the shank, and the underside of the fluke comprising three flat surfaces lying respectively in mutually different planes each of which intersects the others along lines parallel with or lying in the said medial plane of the shank.

Further, according to a third aspect of the present invention, there is provided an anchor comprising a plate-like fluke composed of a central sole lying in a plane normal to a plane of symmetry of the anchor, the sole having a longitudinal fore-and-aft dimension in a direction of the line of intersection of the sole and symmetry planes and a transverse dimension parallel to the sole plane and perpendicular to the said intersection line, the sole extending longitudinally and forwardly from a heel to two toes lying respectively on opposite sides of the symmetry plane, and also composed of two lugs transversely spaced apart by the sole, both lugs being inclined at equal acute angles from and to one side of the sole plane and each lug having a longitudinal fore-and-aft dimension less than that of the sole and extending forwardly from the heel to a toe of the lug, the anchor also comprising a cranked shank having a medial plane coincident with the symmetry plane, the shank being composed of a first leg joined at one end to the heel and extending from the heel to a knee spaced from and to the one side of the sole plane and a second leg extending forwardly from the knee to a free end adapted to be attached to a chain, cable or rope.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure l is a side elevation of an anchor in accordance with the present invention; Figure 2 is a rear view in the direction of arrow A in Figure 1; Figure 3 is a plan view in the direction of arrow B in Figure 1; Figure 4 is a side elevation of part of an anchor similar to that shown in Figure 1, but incorporating a modification; Figure 5 is a side elevation of a second embodiment of an anchor in accordance with the present invention; Figure 6 is a plan view of the anchor shown in Figure 5; Figure 7 is a rear view of the anchor shown in FigureS; Figure 8 is a front view in the direction of arrow C in Figure 5; and Figure 9 is a three dimensional view from above of an anchor similar to that shown in Figures 5 to 8, but incorporating a modification.

Figures 1 to 3 of the drawings are of a schematic nature and not to scale. In these figures, the anchor consists of a single fluke 10 which is fixed with respect to a shank 11 of generally L-shape having a longer leg 1 lea and a shorter leg 1 1b. In Figure 1, the general length dimensions of the legs 1 1a and 1 1b are represented by references S1 and S2 respectively. For practical purposes, the ratio Ski :52 will be in the range 0.3 to unity. The forward or free end portion of the leg 1 la is provided with a shackle hole 12 for the connection of an anchor chain or the like.

The shank 11 is provided with a second connection point at 13 for the connection of a pennant or trip chain or cable in conventional manner. The medial plane of the shank 11 is indicated in Figures 2 and 3 by reference numeral 14. The fluke 10 is disposed at the end of the shorter leg 1 ib of the shank 11 symmetrically with respect to the medial plane 14 and is of plate-like configuration the underside of which defines three flat surfaces designated by reference numerals 10a and 10b. The surface 10a constitutes the sole of the fluke 10, and the two surfaces 10b constitute the undersurfaces of fluke side lugs 15. The surfaces 10a and 10b lie in three mutually different planes as seen in Figure 2 each of which intersects the others along lines parallel with or lying in the medial plane 14.In Figure 3, the said lines parallel with the medial plane 14 are indicated by reference numeral 16 which lines may also be regarded as fold lines between the sole portion of the fluke 10 and the lugs 1 5.The angle between the undersurface of each lug 15 and the sole of the fluke is designated E in the drawings and this angle for practical purposes is in the range 30 to 60". The general outline configuration of the fluke 10 as seen in plan view includes lines defining leading edges 17 which are swept back symmetrically on each side of the medial plane 14to include an angle designated D in Figure 3.For practical purposes, the angle D will lie in the range 50 to 1200. The trailing edges of the lugs 15 are swept forwards from the heel 18 of the fluke 10 so that the outer extremities of the lugs 15 define points 15a and the lugs 15 are of generally triangular configuration. The shank 11 is generally set at an angle to the sole of the fluke 10 as seen in Figure 1. Thus, the centre line of the leg 1 la and the centre line of the fluke lOin the medial plane 14 include an angle F which for practical purposes will lie in the range 5" and 20 . The overall fore-and-aft length dimension of the fluke 10 is designated L in Figure 1, and the overall width in plan of the fluke 10 is designated W in Figure 3.For practical purposes, the ratio L:W will be equal to or less than unity. The centre of gravity of the anchor lies in the medial plane 14 in the vicinity designated 19 in Figure 1. The position of the centre of gravity of the anchor is such that the anchor is stable when resting on a generally horizontal surface or mooring bed on the free end of the shank 11 and one or other of the swept back leading edges 17. In addition, the anchor described with reference to Figures 1 to 3 is also stable on a generally horizontal surface when resting on the sole of the fluke, when resting on the rear of the leg 1 ib and the heel 18, and when resting on the length of the leg 1 lea and either of the points 15a.

The anchor described above is self-burying in a mooring bed of penetrable material when the anchor is dragged by an anchor cable attached to the point 12 on the shank 11. Regardless of the initial attitude of the anchor on contacting the mooring bed, the free end of the shank 11 will, in most conditions, tend to be brought quickly into contact with the mooring bed by virtue of the weight of the anchor cable and the drag action. When the free end of the shank 11 is thus disposed, it can be seen by general inspection of the configuration of the anchor that continued dragging action will result in one or the other of the leading edge portions 17 of the fluke 10 adopting a scooping orientation with respect to the mooring bed.On further drag action, due to the symmetry of the fluke, the inclined lugs 15 and the parallel relationship between the planes on the under surfaces of the fluke the anchor tends to adopt a stable attitude with the sole of the fluke lowermost and the leg 1 lea of the shank 11 generally horizontal.

In this attitude, the fluke 10 is capable of continued blade-like penetration of the mooring bed material involving principally frictional shear between said material and the surfaces of the fluke and minimally involving significant disturbance of the mooring bed material. During the penetrating action of the anchor, the flat surfaces constituting the underside of the fluke act against any tendency of the anchor to roll or rotate on an axis substantially coincident with the direction of drag force in the anchor cable at the connection point 12. When the anchor has reached a depth of penetration sufficient to establish a holding power equal to the drag force in the anchor cable, the flat surfaces constituting the underside of the fluke improve the holding power of the anchor particularly in mooring bed materials consisting of soft mud and the like.

Bearing in mind the operation of the anchor as described above, it will be understood that the final scantlings for any one design of anchor will depend to some extent on the nature of the mooring bed material expected to be encountered, and to some extent it will be understood that final dimensions may best be determined by experiment. In all designs for mooring beds of penetrable material, improvement in respect of stability against "rollout" and in respect of holding power is derived from the flat characteristic of the undersurfaces of the fluke and from the intersections of the surfaces lying on lines parallel with or in the medial plane of the shank.

Breaking out of the anchor described above is effected in the conventional manner by progressive- ly reducing the scope of the anchor cable so that a generally upward pull can be exerted on the free end of the shank 11. The upward pull effectively causes the anchor to swing rearwardly about the heel of the fluke so raising the fluke so that the anchor can be withdrawn from the mooring bed. In the event that withdrawal of the anchor presents difficulty due to fouling, a cable with a chaser loop for running down the existing anchor cable may be used to extract the anchor when the chaser loop embraces the knee between the legs 1 la and 1 16 of the shank 1 1.

In Figure 4, the fluke 10 is modified by the presence of a vane or wall member 20 which extends fully across the heel of the fluke and co-operates with rearward extensions 15b of the lugs 15 to form a scoop-like configuration at the rear of the fluke.

This modification is intended for use particularly in very soft muddy conditions of the mooring bed.

During laying of the anchor in these conditions, it is desirable to augment the total of downward forces urging the anchor to effect self-burial. During dragging of the anchor, the vane orwall member 20 upwardly deflects material exiting rearwardlyfrom the top surface of the fluke and this upward deflection achieves the objective stated above. Also, the presence of the vane or wall member 20 improves the holding power, particularly of very large anchors, in mooring beds af soft mud.

In Figures Sto 8 inclusive, parts corresponding with those in Figures 1 to 3 are given the same reference numerals as used in Figures 1 to 3. Figures 5to 8 are generally to scale and show one preferred form of anchor in accordance with the present invention. Whereas the anchor of Figures 1 to 3 is suited particularly to conditions where the mooring bed is of penetrable material, the anchor of Figures 5 to 8 is of general purpose application and is useful in a wider range of mooring bed conditions. As can be seen from the drawings of Figures Sto 8, the fluke 10 incorporates the three flat undersurfaces as already described. In addition, the forward portion of the fluke 10 defines two pairs of forwardly extending fingers or toes which are disposed symmetrically with respect to the medial plane 14 of the shank 11.

Toes 21 form one of said pairs, and toes 22 form the other pair. The insides of toes 21 are formed by the sides 23 of a slotted or re-entrant configuration of the fluke as seen in plan on the fore-and-aft centre line of the fluke. The insides 24 of the toes 22 are similarly formed by respective further slotted or re-entrant configuratons of the fluke as seen in plan on the lines 16 parallel with the medial plane 14.

The manner of operation of the anchor of Figures 5 to 8 is similar to that already described with reference to Figures 1 to 3 in conditions where the mooring bed material is readily penetrable. In conditions where the mooring bed material tends to be less easily penetrable, the presence of the toes 21 and 22 promotes breaking up of the mooring bed material in the vicinity of these toes and so assists generally in penetration during burying action of the anchor. In mooring bed conditions of generally impenetrable character, the toes 21 and 22 provide an improved means for engagement with mooring bed projections, outcrops and the like. The absence of a fluke point, as can best be seen in Figures 6 and 8, reduces the risk of the anchor making a single point contact which is more easily lost by subsequentyawing or rolling.

In penetrable mooring bed conditions, when the anchor is buried and holding, most of the holding forces are generated by the central, side and rear portions of the fluke 10. The presence of the spaces between the toes 21 and 22 provides an additional advantage of facilitating break-out of the buried anchor by reducing the moment requred to turn the buried anchor about the heel of the fluke.

For the anchor of Figures 5 to 8, the following are approximate values. The angle D - 70 ; the angle E - 45 ; the angle F - 15 ; the shank leg ratio S2:S1 0.54, and the fluke length to width ratio L:W - 0.8.

The anchor of Figure 9 is the same as the anchor of Figures 5 to 8 with the addition of blade elements 25 which are secured in the re-entrant portions of the fluke between the toes 21 and 22. The blade elements 25 each consist of a flat metal bar shaped to fit the respective re-entrant or slotted configuration and chamfered at its forward ends to a cutting edge. The width dimension of each cutting element 25, that is the dimension transverse to the sole of the fluke 10, is constant and equal to the thickness of the fluke at the inner end of the slotted configuration.

The lower edge of each cutting element is flush with the fluke sole surface. Thus, the upper edges of the cutting elements stand proud of the fluke at the leading edges thereof and merge with the fluke rearwardly of these leading edges due to the divergent upper surface of the fluke as described hereinafter. The cutting elements 25 improve the penetrative ability of the leading portion of the fluke 10 in certain mooring bed conditions of less penetrable nature, and also improve lateral stability when buried.

Anchors in accordance with the present invention and as described above, may be manufactured either by a casting process or by fabrication using steel plate or other material. The latter method of manufacture is preferred particularly for anchors at the heavier end of the range where casting becomes difficult and costly. The anchor of Figures 5 to 8 described above comprises a fabricated and welded assembly of flat steel plates. In particular, the fluke of Figures 5 to 8 consists of undersurface plates and top surface plates bounding a hollow interior, the top surface plates diverging from the under surface plates and merging on the lines 26 and 27 as seen in Figure 6. This form of construction provides rigidity and strength in the fluke and improves the holding power/weight ratio of the anchor.

One modification of the anchors described above within the scope of the appended claims is the use of a straight shank in place of the L-shaped shank described. In such a modification, the anchor would no longer be so reliably self-burying on being dragged by the anchor cable due to the fact that the presence of the knee portion of the L-shaped shank makes an important or essential contribution to the orienting of the fluke in the automatic self-burying action. In another modification of the anchors described above within the scope of the appended claims, the L-shaped configuration of the shank may incorporate a degree of curvature conferring a hook like appearance so that the inner or shorter leg of the shank approaches the fluke from the rear thereof less steeply than shown in the illustrated embodiments. It is, therefore to be understood that the expression "generally L-shape" is to be construed as including a modification such as that just described.

A further modification of the anchor of Figures 1 to 3 within the scope of the appended claims includes dispensing with the swept back foremost portion of the sole of the fluke 10. This modification would be operable in easily penetrable mooring bed conditions and would represent the lower practical limit for the ratio of fluke length to overall width as previously referred to herein.

Claims (15)

1. An anchor having a single fluke fixed with respect to a shank of generally L-shape, the fluke being disposed at the end of one leg of the shank symmetrically with respect to the medial plane of the shank, and the underside of the fluke comprising three flat surfaces lying respectively in mutually different planes each of which intersects the others along lines parallel with or in the medial plane of the shank.

2. An anchor according to claim 1, wherein two of said flat surfaces disposed respectively on opposite sides of the said medial plane extend upwardly and outwardly from the third surface each at an angle in the range 30" to 60 to the plane of said third surface the latter surface constituting a sole of the fluke.

3. An anchor according to claim 1 or 2, wherein the general outline configuration of the fluke as seen in plan view includes lines defining leading edges swept back symmetrically on each side of said medial plane.

4. An anchor according to claim 3, wherein the angle included by the lines defining the said leading edges is in the range 50 to 120 as seen in plan view.

5. An anchor according to any one of claims 1 to 4, wherein the forward portion of the fluke defines at least one pair of forwardly extending fingers or toes disposed symmetrically with respect to the said medial plane.

6. An anchor according to claim 5, wherein a first pair of said toes or fingers is defined in part by the sides of a slotted or re-entrant configuration of the fluke as seen in plan on the fore-and-aft centre line of the fluke, and the toes or fingers of a second pair of toes or fingers are defined in part by respective further slotted or re-entrant configurations of the fluke as seen in plan on the said lines parallel with the said medial plane.

7. An anchor according to any one of the preceding claims, wherein the centre lines of the fluke and of the leg of the shank remote from the fluke in said medial plane include an angle in the range 5" to 20 diverging in the forward direction of the fluke.

8. An anchor according to any one of the preceding claims, wherein the shank has one leg shorter than the other, and the fluke is disposed at the end of the shorter leg.

9. An anchor according to any one of claims 2 to 8, wherein the ratio of the overall length fore-and-aft to the overall width in plan of the fluke is equal to or less than unity.

10. An anchor according to any one of claims 2 to 9, wherein said two flat surfaces disposed respectively on opposite sides of the said medial plane are defined respectively by the undersides of two lug portions of the fluke, each said portion being of generally triangular configuration.

11. An anchor according to any one of the preceding claims including a vane or wall member arranged adjacent the trailing or rear edge of the fluke transversely of said medial plane for deflecting upwardly material exiting rearwardly from the top surface ofthefluke.

12. An anchor according to any one of the preceding claims, wherein the fluke comprises an assembly of flat plates.

13. An anchor having a single fluke fixed with respect to a shank, the fluke being disposed at one end of the shank symmetrically with respect to a medial plane of the shank, and the underside of the fluke comprising three flat surfaces lying respectively in mutually different planes each of which intersects the others along lines parallel with or lying in the said medial plane of the shank.

14. An anchor comprising a plate-like fluke composed of a central sole lying in a plane normal to a plane of symmetry of the anchor, the sole having a longitudinal fore-and-aft dimension in the direction of the line of intersection of the sole and symmetry planes and a transverse dimension parallel to the sole plane and perpendicular to the said intersection line, the sole extending longitudinally and forwardly from a heel to two toes lying respectively on opposite sides of the symmetry plane, and also composed of two lugs transversely spaced apart by the sole, both lugs being inclined at equal acute angles from and to one side of the sole plane and each lug having a longitudinal fore-and-aft dimension less than that of the sole and extending forwardly from the heel to a toe of the lug, the anchor also comprising a cranked shank having a medial plane coincident with the symmetry plane, the shank being composed of a first leg joined at one end to the heel and extending from the heel to a knee spaced from and to the one side of the sole plane and a second leg extending forwardly from the knee to a free end adapted to be attached to a chain, cable or rope.

15. An anchor substantially as hereinbefore described with reference to and as shown in Figures 1 to 3, or Figures 5 to 8, or Figure 4, or Figure 9 of the accompanying drawings.