US2674969A - Mooring anchor - Google Patents

Description

April 13 1954 MooRING ANCHOR Filed Dec. 4, 1952 for use.

Patented Apr. 13, 1954 MORING ANCHOR Richard S. Danforth, Berkeley, Calif., assignor to Robert H. Eckhoff, Piedmont, Calif., as

trustee Application December 4, 1952, Serial No. 324,262

8 Claims.

This invention relates to mooring anchors. This is a continuation-impart of my application Serial No. 35,349, filed June 26, 1948, and which has since been formally abandoned, and of application Seri-al No. 156,182, filed April 15, 1950,

land now abandoned.

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

The pivoting fluke anchor isithat commonly used today on most merchant ships and by mam7 navies because of the ease with which it can be drawn into a hawse pipe and held there ready 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 dukes simultaneously engage the ground. The pivoting fluire type anchor can have a stoel; 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 iiulres, either by lifting the rear end, as in the Danforth anchor, or by rotating the nukes, as in the old style stoclrless anchor.

The mooring anchor is utilized to provide a mooring of a incre or less lpermanent nature. vSuch a mooring usually includes one or more buoys connected to come means for engaging bottom Awith relativeli great security and permanence. Permanent moorings are laid for numerous reasons, e. g., to insure that a moored ship will not drag even vin 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 labsolute 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 areplaced in position and connected singly or in groups to one or more buoys which are engaged by a ship wishing to moor.

The hedge anchor, the pivoting duke anchor and the mooring anchor have entirely different modes of action. For example, a hedge anchor having a stock at the forward end of the shank will usually rst engage bottom rwith one end of the stock and the two fluke arms touching bottom. As an anchor is pulled, it gradually tips over until the tip of one iiulze engages bottom and the stoel?. is approximately parallel with the bottom on which it rests. Upon further drag on the anchor, the tip of the` duke enters and the anchor buries to some extent. Tie usual hedge anchor will not bury deeply in hard ground, this being confined to the `palm and part of the fluke arm, the rest of the anchor being above bottom. Although a great deal of research has been done, as shown by the thousands of issued patents throughout the world, there have been no radical improvements in this type of 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 fluke and the cable end of the shank. As the anchor is dragged, the ulre will immediately enter the ground and the anchor will gradually turn to a position where the stock is parallel or nearly so to bo-ttom.

In the pivoting fluke types of anchor, the anchor will rest flat on the bottom it 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 linkes will be inclined upwardly from the surface of the bottom. The anchor has to be dragged for some distance before the flukes will turn and enter the bottom. It is necessary to provide an extensive and eilective lifting or rotating mechanism at the after end of the anchor to start the nukes penetrating bottom. lf the lifting or rotating action on the flukes is effective, the flukes 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 or 20 feet before it develops any degree of holding power, while the lifting or rotating device at the rear of the anchor provides considerable resistanceto deep burial.

I have discovered that the holding power of a mooring anchor can be increased greatly to provide an anchor capable of holding more than any anchorof any type if the mooring anchor embodies certain presently related structural re lationships.

In use, the mooring anchor of this invention, when properly placed on bottom, is ready for instant use and is capable of providing substantial holding power immediately a pull is applied to its shank. Further, the mooring anchor of this invention is capable of such deep penetration into bottom that the anchor, in eifect, becomes locked therein because the bottom is so dense that the anchor cannot penetrate further. This assures excellent holding in even the softest bottoms because the mooring anchor of this invention will continue to bury itself until it has come to rest in hard dense bottom and cannot go deeper. The advantages and value of this are manifest to any one desiring a reliable mooring.

It is in general a broad object of the present invention to provide an improved anchor especially suited for use as a mooring anchor.

Another object of the present invention is to provide an improved mooring anchor wherein relatively high holding power per pound of weight of the anchor is provided.

A further object of the present invention is to provide a mooring anchor having a shank, stock, and nukes, and wherein the area of the nukes is located in such relation to the point of cable attachment and bears such a relation to the resistance area as to ensure continued penetration of the anchor into bottom until the anchor is nrmly seated in hard bottom.

An additional object of the invention is to provide a mooring anchor which can be manufactured easily and of relatively low priced materials, and which has high unit holding power so that the anchor provides Very inexpensive mooring.

The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter when the present preferred form of mooring anchor of this invention is disclosed.

In the drawings, Figure 1 is a side elevation of an anchor embodying the present invention.

' Figures 2, 3, 4 and 5 are, respectively. sections taken along the lines 2 2, 3 3, 4 4 and 5 5 of Figure 1.

Referring to the drawings, I have shown a structure including a shank 6, a single nxed nuke 1 having a rib I4 extending centrally of the nuke and welded to the shank as at It. At the rear of the shank a stock 8 is provided, this extending through a suitable aperture in the shank E and the nukes extending rearwardly and being welded to the stock so that a rigid structure is provided. The stock 8. however. may be at the forward end of the shank, 'if desired, and the anchor can be made of cast or forged parts or those cut from plate or other structural elements.

The shank is preferably tapered, being somewhat thinner at the forward end; this is ap" parent from. considering the several sectional thicknesses shown in Figures 3, 4 and 5. The underside of the shank is preferably made with a V, as at Il, to permit of ready penetration of bottom.

The shape of the nuke should be such as to enable it to engage bottom quickly and to penetrate bottom readily. To this end, the 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 as isv consistent with the other desired anchor characteristics. I have found that if one provides the nuke of such shape that' it has an entrance angle of between 35 and 55, preferably about 45,

, wardly from the apex of the triangle, the latter corresponding approximately to the point of the nuke. Since the outer edge of the nuke can be straight or curved or can be various combinations of straight and/or curved portions, resort must be had to an approximation of this nature to care for the various shapes which can be employed.

For the purposes of discussion and to enable the various essential dimensional and proportional relations to be readily understood, the following additional'dennitions and dimensions are employed in defining the mooring anchor of this invention.

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

Line BC is the axis of the 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 in a plane substantially parallel to the forward or advancing face of the nuke. The point I is the center of area of the nuke face; this point can be determined by application of usual and known geometric meth ods to those portions of the nuke face which provide the effective holding power of the anchor, it being unnecessary to take into account small nuke areas which, while possibly part of a nuke,

contribute little if anything to the anchor holding power and which otherwise make the ascertainment of the center of area of the entire nuke forward faces relatively difficult. The eiective shank length is the distano 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 nuke and is the distance between the point of the nuke and the rearward effective edge thereof; in the form shown in the drawing the rearward effective t edge on the nuke is substantially coincident with the stock axis DE.

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

The nuke angle, as indicated in Figure 1, is the angle between the axis BC of the shank and a plane GH, substantially parallel to the nuke 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 attach ment A and the areal center I of the effective nuke forward face.

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 nuke.

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

The nuke area is that portion of the forward face of the fluke which is effective to provide holding power in bottom engagement; in the form of anchor shown it comprises the entire area of the nukes. angularly .formed along its longitudinall axis, its

If the nuke is curved or is I Figure 1 `between the point of cable attachsrrrent A and the areal center I of the fluke area.

In the preferred. form of anchor shown in the drawing, the fluke 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 cut, 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 and even higher; it is also obviously possible to make the nuke, or at least some portion thereof, arcuate in transverse section. In this same connection, it must be pointed out that the nuke can be made with at least some portion of it in arcuate form along the longitudinal axis as well as the transverse axis. The effect of such variations on the operational characteristics and values is generally only slight at the most. In applying the teachings of the present invention to anchors wherein such arcuate or angular modifcations are introduced, one should generally make an approximation on 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 fiat 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 rela.- e.

tions to one another, as follows:

The relation of the uke 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 fluke 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 tou 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 cf 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 following table this variation is shown for anchors of different weights, the several anchors being made of the same material, in the same design and with the same strength:

n -5 Ou In addition to the foregoing, the mooring `anchor should have a stock adequate to prevent rotation and to ensure that the anchor initially rests on the end of the stock, a point of one of the nukes and an end of the shank; the stock should be from '75% to 85%, preferably 95% or more of the shank length. The stcckrcan be at either end of the shank, although it is preferable to have it at the after end oi the shank.

To ensure easy penetration, the anchor should have an atta-ck angle, as previously defined, of from to 55, preferably one in the range of -50 and even more desirablybetween 33 and 48.

The point angle should also be between 50-80 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 cf itself it is not a vital determinant; if it is in the range of 25 to 39'and preferably 28 to 35, conditions are usually satisfied; the preferred angle is of a value of 30 for cast steel anchors and 34% for anchors made of'plateand structural steel.

Anchors of this design have been proved in tests by government authorities to have from seven to ten times the holding power of mooring anchors previously used.

I claim:

1. An anchor consisting solely ofa 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 fluke disposed symmetrically on each side of said shank, said fluke beinga thin flat plate extending fxedly forward from a junction with the stock atan angle to the shank of from about 25 to about 39, the outer edges of said fluke providing an entrance angle, as herein defined, of from about 35 to about 55, said fluke having a sharp terminal end at its forward end, the fluke having its rear terminal end secured to the stock on each side of the shank, the ratio of the area of said fluke to the square of the shackle distance, as shackle `distance is herein delined, being greater than 0.16, the stock having a length of at least of the length of the shank, the anchor having an attack angle, as herein defined, of between 25 and 55..

2. An anchor consisting solely of va 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 fluke disposed symmetrically 0n each side of said shank, said fluke being a thin fiat plate of generally triangular shape and extending fixedly vforward from a junction with the stock at an angle to the shank of from about 25 to about 39, the outer edges of said fluke being at an angle t0 one another and defining a sharp terminal forward end, the fluke having its rear terminal end secured to the stock on each side of the shank, the ratio of the area of said fluke to the square of the 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.

3. 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 fluke disposed symmetrically on each side of said shank, said fluke extending 'I xedly forward in a single plane from a junction with the stock at an angle to the shank, the outer edges of said fluke dening a sharp terminal end, the fluke having its rear terminal end secured to the stock on each side of the shank, the ratio of the area of said fluke 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.

4. An anchor consisting solely of a shank having a forward 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. iiuke disposed symmetrically on each side' of said shank, said fluke being a thin flat plate triangularly shaped and extending flxedly forward from its junction with the stock at an angle to the shank of from about 28 to about 36, the outer edges of said iluke providing an entrance angle, as herein defined, of about 45, said nuke having a sharp terminal end, the fluke having its rear terminal end secured to the stock on each side of the shank, the ratio of the area of said fluke to the square of the shackle distance, as shackle distance is herein defined, being greater than 0.16, the stock having a length of at least 85% of the length of the shank, the anchor having an attack angle, as herein defined, of between 30 and 50.

5. A fixed fluke anchor comprising 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 Va common plane; and a fluke secured in a position of fixed angular relationship at the after end of the shank and disposed symmetrically oneach side of the shank and terminating in a single terminal end; said fluke extending forwardly from its connection with the shank in approximately a single plane, with its rear edge substantially intersecting said common plane at the after end of the shank; the longitudinal axis of the stock being substantially parallel to the plane of the nuke; the fluke area to shackle distance ratio, as herein delined, being greater than 0.16; the resistance area to shackle distance ratio, as herein deiined, being less than about 0.20, whereby the anchor has a minimum of resistance to burial.

`6. A fixed fluke anchor comprising 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 dening a common plane; and a iiuke secured Iin a position of xed angular relationship at the after end of the shank and disposed symmetrically on each side of the shank and terminating in a single terminal end; said fluke extending forwardly from its connection with the shank in approximately a single plane, with its rear edge substantially intersecting said common plane at the after end of the shank; the longitudinal axis of the stock being substantially parallel to the plane of the fluke; 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; the attack angle, as herein dened, being from 25 to 55, whereby the anchor has a minimum of resistance to burial.

7. A fixed fluke anchor comprising 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 fluke secured in a position of fixed angular relationship at the after end of the shank and disposed symmetrically on each side of the shank and terminating in a single terminal end; said fluke extending forwardly from its connection with the shank in approximately a single plane, with its rear edge substantially intersecting said common plane at the after end of the shank; theilongitudinal axis of the stock being substantially parallel to the plane of the fluke; the fluke area. to shackle distance ratio, as here-in deiined, being greater than 0.13; the resistance area to shackle distance ratio, as herein defined, being less than about 0.20; the point angle, as herein defined, being from 50'to 80, whereby the anchor has a minimum of resistance 'to burial. Y

8. A fixed flukeanchor comprising the follow*- ingV structural elements: a shank having'a forward and an after end; a stock connected to and g 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 nuke secured in. a position of fixed angular relationship at the after end of the shank and disposed symmetrically on each side of the shank and terminating in a single terminal end; said fluke extending forwardly from its connection with the shank in approximately a single plane, with its rear edge substantially at the after end of the shank; the longitudinal axis of the stock being substantially parallel to the plane of the fluke; the ratio of the area of said fluke 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 the shank; the anchor having an attack angle, as herein defined, of between 25 and 55, whereby the anchor has a minimum of resistance to burial.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain May 4, 1864

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