US2674968A - Mooring anchor - Google Patents

Description

April 13, 1954 R. s. DANFORTH 2,674,968

MooRING ANCHOR 4f rneys d I A /1 MEMBER 0F T//E FIR April 13 1954 R. s. DANFORTH 2,674,968

MooRING ANCHOR Filed Feb. '7, 1952 4 Sheets-Sheet 2 Erz rance Hug/e IN V EN TOR,

April 13, 1954 R. s. DANFORTH MOORING ANCHOR 4 Sheets-Sheet 3 Filed Feb. 7, 1952 Ec/HoFF I :5L/CK nTr RNEYS a l ,Q By A MEMBER 0F THE .FIRM

April 13, 1954 R. s. DANFORTH MQORING ANCHOR 4 Sheets-Sheet 4 Filed Feb. 7, 1952 Patented Apr. 13, 1954 MOORING ANCHOR Richard S. Danforth, Berkeley, Calif., assigner to Robert H. Eckhoif, Piedmont, Calif., as

trustee Application February 7, 1952, Serial No. 270,343

8 Claims. 1

This invention relates to mooring anchors. This is a continuation-in-part of my application Serial No. 35,349, nled June 26, '1948, and which has since been formally abandoned, and of application Serial No. 156,182, nled April l5, 1950.

Generally, anchors can be divided into three major groups, the kedge or` old fashioned stock anchor, the pivoting nuke or stockless anchor, and the mooring anchor. The kedge anchor includes a shank from one end of which projects two opposite extending curved arms carrying nukes or palms. The shank is provided with a long bar or rod providing a stock, the latter extending in a plane transverse to that of the nuke arms so that one arm and its palm engage bottom; the stock can be at either end of the shank.

The pivoting nuke anchor is that commonly used today on most merchant ships and by many navies because of the ease with which it can be drawn into a hawse pipe and held there ready for use. Its principal characteristic is that it includes a shank and twin nukes, usually secured together as a unit and pivoted at one end of the shank whereby the nukes simultaneously engage the ground. The pivoting fluke type anchor can have a stock at either end of the shank; in the commonest form of this anchor,` the stock is omitted. It must also include a crown structure to cause initial engagement of the nukes,

either by lifting the rear end, as in the Danforth anchor, or by rotating the nukes, as in the old style stockless anchor.

The mooring anchor is utilized to provide a mooring of a more or less permanent nature. Such a mooring usually includes one or more buoys connected to some means for engaging bottom with relatively great security and permanence. Permanent moorings are laid for numerous reasons, e. g., to ensure that a moored ship will not drag even in heavy weather; no ship relies on her anchors and cables without being able to move under her own power upon reasonably short notice and, for this reason, a permanent mooring must provide practically absolute security against dragging. Permanent moorings are also utilized to preserve ships anchors and cables from wear and tear, to make use of limited space by providing berths suitable for all classes of ships using a port. and to facilitate port administration by enabling ships to come and go with a minimum of outside help with certainty of position to be taken. The actual ground engaging means utilized in a permanent mooring includes various forms of heavy weights and anchors which are placed .in position and connected singly or in groups to one or more buoys which are engaged by a ship wishing to moor.

It has heretofore been proposed to utilize a mooring anchor which can be said to be of the kedge type in that the nuke is fixed relative to the shank and does not pivot. Such anchors have usually been made by cutting off an arm and its attached nuke from an ordinary kedge anchor. All mooring anchors known prior to this invention included a single nuke supported in a spaced relation to the shank by an arm.

rlhe kedge anchor, the pivoting nuke anchor and the mooring anchor have entirely dinerent modes of action. For example, a kedge anchor having a stock at the forward end of the shank will usually nrst engage bottom with one end of the stock and the two `nuke arms touching bottom. As an anchor is pulled, it gradually tips over until the tip of one nuke engages bottom and the stock is approximately parallel with the bottom on which it rests. Upon further drag on the anchor, the tip of the nuke enters and the anchor buries to some extent. The usual kedge anchor will not bury deeply in hard ground, this being confined to the palm and part oi' the nuke arm, the rest of the anchor being above bottom. Although a great deal oi research has been done, as shown by the thousands of issued patents throughout the world. there have been no radical improvements in this type ci' anchor for some two thousand years.

In a kedge anchor with the stock aft, the action differs in that the anchor rests initially upon one end of the stock, the tip of one nuke and the cable end of the shank. As the anchor is dragged, the nuke will immediately enter the ground and the anchor will gradually turn to a position where the stock is parallel or nearly so to bottom.

In the pivoting nuke types oi anchor, the anchor will rest nat on the bottom ii this will support the anchor; if the bottom is soft, the rear and heavier end of the anchor will be 'buried in the soft bottom while the nukes will be inclined upwardly from the surface of the bottom. The anchor has to be dragged for some distance before the nukes will turn and enter the bottom. It is necessary to provide an extensiveand eifective lifting or rotating mechanism at the after end of the anchor to start the nukes pene trating bottom. If the lifting or rotating action on the nukes is effective. the nukes will turn as the anchor is dragged along, and the anchor will gradually penetrate bottom to some extent, depending on the design. It is usually necessary to drag a pivoting fluke type of anchor 15 to 20 feet before it develops any degree of holding power, While the lifting or rotating device at the rear of the anchor provides considerable resistance to deep burial. y i

I have discovered thatl 'the holding power of a mooring "anchor can be increased greatly to provide an anchor capable of holding more than any anchor of any type if the mooring anchor embodies certain presently related structural rela*- tionships. p

In use, the mooring anchor of this invention, when properly placed on bottom, -isready for instant use and is capable of providing substantial holding power immediately agpull 'is applied to its shank. Further, the mooring anchor of this invention is capable of such deep penetration'into bottom that the anchor, in effect, becomes locked therein :because the bottom isso densethat 'the anchor can-notv penetrate f-tirther.. This :assures excellent holding in even thev softest bottoms because the mooring anchor of this invention will continue to vbury itself until it .has ycome to rest in hard dense bottom yand cannot `go deeper. The advantages `and value lof 'this are manifest to lany `onedesiring fa reliable mooring.

It is ini-general 'a broad :object of 'the lpresent invention to provide an improved anchor. especially suited for -use fas a. mooring anchor.

vAnother object l`of ithepresent invention is to provide an impro-ved mooring .anchor wherein relativelylhigh holdingipcwerper pound of weight of the anchor Hisprovided `A further'object of itherpresent invention is to provide a mooring anchor having.. a shank, stock, and nukes-:and wherein -the area vof Ythe .flukes is located in such-relation to :the point lof Vcable attachment -andbears-such La relation .to the resistance area-.as .to .ensure continued .penetration ofthe anchor into bottoni until the anchor is firmly seated. i-nhard bottom.

An additional object of the invention :is topro vide ka mooring lanchor which can bemanufao.- tured easily and of'rel'atixrely .low :priced materials,-and .which has high. unit holding v.power so that the anchor .provides very inexpensive nioorm ing.

The invention includes other .objects -and features of` advantages'ome oirvhich, together with the foregoing, :will .appear :hereinafter when the present preferred form 'of mooring anchorfof this invention Ais disclosed.

In the drawings, i

`Figure 1 isa side elevation of an anchor embodying the present invention.

Figure 2 is a section taken along .the line l1TI of Figure 1.

.Figure 3 '.is..a plan .of the .anchor shown in Figure l, while Figure 4 is a section :taken `along the line .9 9 in Figure 3.

Figure 5 is aplan view -of a modiied form of anchor embodying the vpresent invention. v

Figure 6 is a section taken along the line v6--6 in Figure 5. v

Figure '7 is a side elevation-of another modied form of anchor, while Figure 8 is a'section similar to Figure 6, but taken on the anchor shown in Figure 7.

Referring to the drawings, I have shown la structure including a vshank `6 and having bifurcated and separate ilukeelernents orpalms la and 'Ibprovided onoppositefsides of the shank.

Each fluke includes vva rib .21 extend-ing-.alongits 4 inner edge joined along its rear edge to the stock 8. The stock 8 is shown at the rear of the fiukes, extending through a suitable aperture in the shank and providing additional support and attachment for the flukes and shank; the stock can, however, be at the forward end of the shank. The anchor can be made of cast or forged parts or of those cut from plate or other structural elements.

Spacer plates 22 are provided between each rib and the rear end of the shank, the ribs, spacer plates and shank being joined together as by welding. To provide additional securing of the ukes with respect to the shank, a V-shaped member 23 is tted over the upstanding portion of the shank and legs 24 thereon are joined to each of the ribs `although such reinforcement is not essential and the ilukes, stock and shank can be `ioined las only by welding. By providing separate twin nukes the holding power of the mooring anchor can be considerably increased but one can unite the twin nukes .and utilize a single iluke extending on opposite sides of -the shank.

The shape of the lukes should be such vas `to enable it to engage bottom quickly and to penetrate bottom readily. 'llo this end, each nuke should have as relatively sharp a point .as is feasible; in addition, the .shape should be such as to offer as little resistance to penetration las lis consistent with the .other desired anchor characteristics. I have found'that if oneprovides the fluke structure with each fluke of such shape that it has an entrance angle of between 171/2" and. 271/2", lpreti-:rab'ly aboutH221/2, then the fluke will have the `desired characteristics in this re,- spect. The entrance angle is measured by laying out a triangle approximating the shape of the forward portion of the fluke, such triangle .containing only about 40% `of the total area of the fluke; the entrance Yangle is then the angle between the two sideswhich extend rearwardly from the apex of the triangle, the latter corresponding approximately to the point of the fluke. Since the outer edge of the fluke `can be straight-or curved or canbe various combinations of vstraight and/or curved portions, resort must be had to an approximation of this nature to care for the various shapes which can be employed. When a single iluke is provided, the entrance angle values are the sum of values given, e. g., .between 35 and 55, and .preferably about 45.

For the purposes of discussion and to .enable the Various essential dimensional and proportional relations to be readily understood, `the following additional definitions and dimensions are employed in dening the mooring anchor of this invention.

A is the pointof cable attachment at the forward end of the shank.

Line BC is the axis of Vthe shank and line DE is the axis of the stock; the two lines intersect, when the stock is .at the rear of the anchor, at point F. The line .GH lies insa plane substantially parallel to the forward or advancing face of the fluke. The lpoint I is the center of area of the fluke faces; this point can be determined by application of usual and known geometric methods to those portions of the ilukeiaces which provide the effective holdingpower of the anchor, it being `unnecessary to ltake into-account-small fluke areas which,*while-possibly part `of a fluke, contribute little if lanything to Athe anchor holding power; and "which iotherwise make theascer 1 tainment of the center of area of the entire fluke forward faces relatively difficult.

The effective shank length is the distance from` the point A of cable attachment to the line DE, the axis of `the stock, when this is provided at the rear of the anchor; it is indicated as dimension S and is referred to as the shank length. The measurement M is the length of the nukes and is the distance between the points of the flukes and the rearward effective edge thereof; in the form shown in the drawing the rearward effective edge on the nukes is substantially coincident with the stock axis DE.

The stock length is the overall length on the axis DE. l

The fluke angle, as indicated in Figure 1, is the angle between the axis BC of the shank and a plane GH, substantially parallel to the fluke forward face.

The attack angle, as indicated on Figure 1, is the angle between projected plane GH and a line passed through the point of cable attachment A and the areal center I of the effective fluke forward faces.

The point angle, as indicated on Figure 1, is the angle between projected plane GH and a line passed through the point of cable attachment A and the point of the nukes.

The resistance area is the total area of the anchor projected parallel to the fluke axis and onto a plane normal to such axis; such a plane is normal to the plane GH.

The fluke area is that portion of the forward face of the iiukes which is effective to provide holding power in bottom engagement; in the form of anchor shown it comprises the entire area of the nukes. If the flukes are curved or are angularly formed along their longitudinal axis, their transverse axis or both, the fluke area is best measured by projectingthe forward faces onto a plane which is tangent or substantially so, to the fluke faces at the center of area so that, in effect, the fluke faces are reduced to planar form. This approximation is desirable because otherwise one cannot compare the various elements and characteristics.

The shackle distance is the distance AI in Figure 1 between the point of cable attachment A and the areal center I of the fluke area.

In the preferred form of anchor shown in the drawing, the fiuke portions on each side of the shank are in the same plane. While this construction is preferred because it enables the several components to be out, shaped and welded together rapidly at low cost and from inexpensive materials, it is possible to fashion the fluke with the opposite fluke portions at a dihedral angle up to 15 and even higher, as is shown in Figures 5 and 6, wherein the flukes 3i and 32 are shown at a dihedral angle of A spacer 33 is provided between the ends of the flukes and the stock 8 to secure the rear ends of the fiukes in place. It is also obviously possible to make the fluke, or at least some portion thereof, arcu ate in transverse section as has been indicated in Figure 8 wherein flukes 34 and 35 are shown as being arcuate in transverse section. In this same connection, it must be pointed out that the fluke can be made with at least some portion of it in arcuate form along the longitudinal axis as well as the transverse axis, as is shown in Figure 7, wherein the fiukes 31 are shown as having an arcuate form along their longitudinal axis. The effect of such variations on the operational characteristics and values is generally only slight at the fn'ost. n applying the teachings of the basis of an equivalent plane surface or straight line, as the case may require, and then apply the teachings, just as if the surface or line was flat or straight. The values given in this respect of the various characteristics are based on the use of plane surfaces and straight lines.

To ensure maximum performance, the several elements of the anchor should have certain relations to one another, as follows:

The relation of the fluke area to the shackle distance is of importance inasmuch as it is this relation which defines the relative position of the point of application of the force tending to pull the anchor into bottom and the center of area of the fluke. Since one is comparing a lineal dimension with an area, one should, for reasons of comparison on an equal basis, deal with the square of the shackle distance. This ratio is referred to hereinafter for brevity as the nuke area-shackle distance ratio. Comparing the fluke area to the square of the shackle distance, the ratio should be greater than 0.13 and even as much as 0.16 to 0.18.

The resistance area to the shackle distance is also of importance. Again, since one is comparing an area to a lineal dimension, the square of the distance is employed. The resistance area should be less than 0.2 the square of the shackle distance and preferably less than 0.1, consistent with adequate structural strength. This ratio will vary somewhat with the size of the anchor because a larger anchor will require a larger mass of metal to provide the same relative strength. In the foliowing table this variation is shown for anchors cf different weights, the several anchors being made of the same material, in the same design and with the same strength:

In addition to the foregoing, the mooring anchor should have a stock adequate to prevent Vrotation and to insure that the anchor initially `either end of the shank, although it is preferable to have it at the after end of the shank.`

. To ensure easy penetration, the anchor should have an attack angle, as previously defined, of from 25 to 55, preferably one in the range of BIV-58 and even more desirably between 33 and 48.

The point angle should also be between 5080" and preferably between 53 and 78, and even more, preferably between 56 and 75.

The fluke angle is not too important; it is usually fixed by other factors and in and of itself it is not a vital determinant; if it is in the range of 25 to 39 and preferably 28 to 36, conditions are usually satisfied; the preferred angle is of a value of 30 for cast steel anchors and 34%o for anchors made of plate and structural steel.

Anchors of this design have been proved in tests by government authorities to have from 7 seven-.to tenit-imes the holdingnower .of mooring anchors previously used.

1 An anchor consisting solely of a shank having a forward andan after end, cable attachment means at the vforward end of the shank. a stock extending normal to the shank at'the after end of the shank, and a pair of nukes disposed symmetrically on each side of said shank, each fluke being a thin flat plate extending xedly forward from a junction with the stock at an angle to the shank of from about 25 to about 39, the .outer edges of each fluke providing an entrance angle, as herein dened, of from about l71/2 to about 27%, said lukes each having a sharp terminal end at their forward end, the flukes having their rear terminal ends Secured to the stock on each side of the shank, the ratio of the area of said flukes to the square of the shackle distance, as shackle distance is herein defined, being greater than 0.15, the stock having a length of at least 75% of the length of the shank, the anchor lhaving an attack angle, as herein donned, of between 25 and 5 5".

2. An anchor consisting solely of a shank having a forward and an after end, cable attachment means at the forward end of the shank, a stock extending Vnormal to the shank at the after end of the shank, and a pair of flukes disposed syrnmetrically on each side of said shank, each nuke being a thin fiat plate of generally triangular shape and extending xedly forward from a junction with the stock at an angle to the shank of from about 2 5o to about 39, the outer edges of said nukes being .at an angle to one another and defining a ,sharp terminal forward end, the. nukes having their rear terminal ends secured to the stock on each Side of the shank, the ratio of the area of said flukes to the square of the shackle distance, as shackle distance is herein dened, being greater than `0.13, the stock having a'length of at least 75% of the length of the shank, the anchor having an attack angle, as herein defined, of between 25 and 55.

.3.. YAn anchor consisting solely of ashank having a forward and an after end, cable attachment means at the forward end of the shank, a stock extending normal to the shank at the after end of the shank, and a pair of fukes disposed symme'trically on each side of said shank, each fluke extending xedly forward in a single plane from a junction with the stock at an angle to the ank, the outer edges of said nukes defining a arp terminal end, .the flukes having their rear terminal ends secured to the stock on each side of the shank, the ratio of the area of said flukes to the square of kthe shackle distance, as shackle distance is herein defined, being greater than 0.13, the stock having a length of at least 75% of the length of the shank, the anchor having an attack angle, as herein defined, of between 25 and 55.

4. An anchor consisting solely of a shank having a forward and an after end, cable attachment means at the forward end of the shank, a stock extending normal to the shank at the after end of the shank, and a `pair oi nukes disposed symmetrically on each side of said shank, each fluke being a thin flat plate triangular-ly shaped and extending iixedly forward from its junction with the stock at an angle to the shank of from about 28 `toabout 36, the-outer edges of said iukes providing an entrance angle, as herein defined, ofl about 22%", said nukes each having a sharp terminal end, the nukes having their rear tersh sh 8 minal ends secured tothe. stock on .cash .side-Qi the shank, the ratio of. thev .area .of saidflukcs to the square .of the shackle distance.. as .shackle distance is herein donned, heine greater than 0.16.

the stock having a 'length 0f. least 85% of the length of the shank, the anchor haringen attack angle.. herein defined, of between 30 and Y.59-

A fixed nuke anchor including the following structural elements: a Yshrunk having a forward andan after end; a stock connected to and eri.- tending normal to the shank at one of. Said ends thereof; cable attachment means at the forward end of the shank; the shank and stock defining a common plane; and a pair of nukes disposed symmetrically with respect to the shank and secured in a position .of fixed angular relationship at the after end of the Shank; Said illkd each having aterminal end and being vdisposed on opposite sides of the shank; each of said flukes extending forwardly from its connection with the shank in approximately a Single plane burial; the fluke area to shackle distance ratio,`

as herein defined, being greater than 0.16; and a resistance area to shackle distance ratio, as herein dened, being less than about 0.20.

6. A xed fluke anchor including the following structural elements: a shank having a forward and an after end; a stock connected to and extending normal to the shank at one of saidV ends thereof; cable attachment means at the 4forward end of the shank; the shank and stock defining a common' plane; and a pair of flukes disposed symmetrically with respect to the shank and secured in a position of xed angular relationship at the after end of the shank; said nukes each having a terminal end and being disposed on opposite sides of the shank; each of said fiukes extending forwardly from its connection with the shank in approximately a single plane with its rear edge substantially intersecting the common plane of the stock and shank at the after end of the shank; the rear end of theY the anchor has a minimum of resistance to burial; the fluke area to shackle distance ratio, as herein defined, being greater than 0.13; theV resistance area to shackle distance ratio, as herein defined, being less than about 0.20; and the attack angle, as herein defined, being from 25 to 55.

7. A ixed nuke anchor including the following structural elements: a shank having a forward and an lafter end; a stock connected to and extending ,norma-l to the shank at one of said ends thereof; cable attachment means at the forward end o f the shankfthe shank and stock defining a common plane; and a pair of flukes disposed symmetrically with respect to the shank and secured in a position of vfixed angular relationship at the after end of the shank; Asaid flukes each vhaving a terminal end and being disposed on opposite sides of the shank; each of said nukes extending forwardly from its connection with the shank in approximately a single plane with its rear edge substantially intersecting the common plane ofthe stock and shank at the after end of -the shank; lthe rear end of the nukes and of the shank'being substantially free of any protuberances at their juncture, whereby the anchor has a minimum of resistance to burial; the fluke area to shackle distance ratio, as herein defined, being greater than 0.13; the resistance area to shackle distance ratio, as herein defined, being less than about 0.20; and the point angle, as herein defined, being frcm 50 to 80.

8. A fixed uke anchor including the following structural elements: a shank having a forward and an after end; a stock connected to and extending normal to the shank at one of said ends thereof; cable attachment means at the forward end of the shank; the shank and stock defining a common plane; `and a pair of ukes disposed symmetrically with respect to the shank and secured in a position of fixed angular relationship at the after end of the shank; said ukes each having a terminal end and being disposed on opposite sides of the shank; each of said fiukes extending forwardly from its connection with the shank in approximately a single plane with its rear edge substantially intersecting the common plane of the stock and shank at the after end of the shank; the rear end of the flukes and of the shank being substantially free of any protuberances at their juncture, whereby the anchor has a minimum of resistance to burial; the ratio of the area of said iiukes to the square of the shackle distance, as herein defined, being at least 0.13; the ratio of the resistance area to the square of the shackle distance, as herein defined, being less than about 0.20; the stock having a length of at least 75% of the length of theshank; and the anchor having an attack angle, as herein dened, of between 25" and 55.-

References Cited in the le 0f this patent UNITED STATES PATENTS Number Name Date Re. 21,841 Northrop et al. June 24, 1941 1,563,451 Stitcher Dec. 1, 1925 2,249,546 Danforth July 15, 1941 2,320,966 Danforth June 1, 1943 FOREIGN PATENTS Number Country Date 1,129 Great Britain May 4, 1864 OTHER REFERENCES Transactions of the Institution of Naval Architects; 1948, pp. 111-153 inclusive. Published by Institution of Naval Architects, 101 Upper Suigrave Street, London S. W. 1.

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