US2380119A - Anchor - Google Patents

Description

y 945. J. K. NOYRTHROP 2,380,119

ANCHOR Eiled March EL 1941 4 Sheets-Sheet 1 2 l F'J'EJE L Fifi-l' j FjE-E;

/5 DIRECTION OF PENETRATION v M /7 L 7 INVENTOR.

JOHN K Noe THEOP A T TOENEYQS'.

y I J. K. NORTHROP 2,380,119 ANCHOR Filed March 31, 1941 4 Sheets-Sheet 2 J'HA Nk Axis INVEN TOR. Jaw/v K [Va/a THEOP Z MQJMM A T TORNE'Y-S' y 1945. J. K. NORTHROP 2,380,119

' ANCHOR Filed March 31, 1941 4 Sheets-Sheet 5 INVENTOR. 'JOHN [C NOAQTHEOP A T TOENE'YS.

July 10, 1945. J. K. NORTHROP ANCHOR Filed March 51, 1941 4 Sheets-Sheet 4 Eli-1.5-

D/HEDRAL ANGLE INVENTOR. JOHN If. No.9 THEOP Patented July 10, 1945 My invention relates to anchors .andlmorezrparticularly to -lightweight ianchors which will :plane into bottom,v and develop .a holdingvpowen-sub stantially-independent of anchor weight;

Among the objects of myinventionare:

To providea lightweight anchorlofmelatively high holding power; to providea-lightweightianchor developing a high holding power-by virtue of planing action under the stress of a, cable pull; to provide a stable anchor; to provide an anchor wherein the stock is a portion of the fluke and aids in the development of 'the'holding' power-pf the anchor; to provide a splitflukeanchor-forming a dihedral angle under a cable pull, in order to stabilize the anchor; to providevan anchorhaving a flukeattachedto a stockat anangle thereto under a cable pull-,which will translate the-"forward pull into a planing motion, imbedding the anchor into the bottom; to provide ananchor maintaining an eficient planing 1 angletending to progress the anchor deeper into the'bottom' as the cable pull increasespto providean anchor having an extensive fluke area with-ashank at tached adjacent" the center ofjpressure; of the fluke; when imbedded 'in'bottom; to providean anchor that is cheap to manufacture,-has great structural strength-for'agiven weight, and; which has a highly effective application" of structural material, and to provide an anchor WhBIEalljfOf the weight is distributed between a fluke; area which is equally effective regardless of howthe anchor may fallon the bottom, anda shank member which is stressed primarily only in tension with a-secondary and comparatively small stress exerted as a bending moment to keep the fiukes at the proper planing angleyandto provide an improved type of anchor-wherein all the parts are designed to facilitat bottom penetration.-

My invention possesses numerous other objects and features of advantage, some of which, .tog'ether with the.foregoing,.wil1 be vsetforth in the following descriptionof specific apparatus cembodying and, utilizing my novel,method,., It .is therefore to, belunderstood that my method is applicable to other apparatus, and that I dol-not limit myself, in any way, to the apparatus of ,the

present application, as I may adopt various other apparatus embodiments,- utilizing-the method, within the scope of the appended, claims.

In the drawings;

Fig. 1 is a top view in. elevation ofone preferred form of myinventionw Fig. 2 is a 1 side gview partly -ing section and partly in elevation of thelancho f of Fig;-l.

Fige 3 is a. rear viewiin elevation of thezanchor of Fig. 1. i Fig; 4 is lanflanglei diagram showingl preferred angularrelationships of. the, anchor parts:. 1 Figs..5;- 6, 7, 8 andQzarediagramsshowingfluke shape modifications; 1

Figs.:110,-: 1 1; 12; and-.13 arerdiagrammatic side views in elevation. showinglznthe: behavioncf the anchor, of Fig; .1 ;during-.@planing into penetrabl'e bottom.

Fi -.114 is areal: view.

position showman-F1510. i

Fig; 15 is a rear, view; in :perspectiveyaof; the anGhor'positioned-in Fig. 12.:

Fig: 116-; is a cross sectional view. of. the: anchor shank; taken as indicated by line l fi l 6 in-FigLi 1,

sliehtz n areedh v In the prior patent issued toimyself eandrHarry M. I;Ge sner; No.1 2,075 82' 7,- dated :April; 6,, 1937', a lightweight: anchor was. .Vdescribed and; claimed; which has an exceptionallyv high-rgholdinga power with-respect to the; weight roi the .anchor; This nc or n on pre rr d a rma ara cterized y he; useof a fluke of thimsection attached, to a; sh nk -in such amanner-that-kthe" fluke presented its tip to bottom'when-lying,on therbottom,

with ya fluke angle; to bottom of approximately 601? This fluke, was maintained at an langle vof approximately 25, to -26? to the shank'axis .line andrconsequently to; the'lbotton line, when; the shank Twa parallel-.-,to bottom afterL penetration ofl thewfluke thereinto; Thus during; penetration the angle of thefiuke to thelbottomv plane changed IrrJ n- GO- at thestart'to 25 +-26", at fullpenetrate tion with intermediate angles occurringas more andmore i of the fluke 1 area; entered the.- bottom. Theholding-power of an anchor built inaccord ance with the previous applicationabove refer-red to,,.is thigh and will vary somewhat in accordance with ,thev thickness and area of theifl uke andsin accordance with the resistancen to v downward travel oi the anchor parts, to give weight :tov hold. ing ppwer ratiosof. over.1.:200.. r I v The anchor of the presentiinventionaisillustrated asv a divided,. balanced fluke anchor: and i a rimprovementeon the formeranchor in, that yj'Pr 1 Q1T-.iS ncapable of epractica'llyum limited penetration into bottom. r Ast a eonsee s quence, any; increaseof:cablepull-om the anchor tends ,to :burythe anchor. still :cle eper because of ,the .planing action thereon 1 This result is accomplished broad-1y. byq attachingathe shank ad- I iacen-t nd pref erably 'just' above the effective center, =01 ;pressureof thel-flukesections andbyho1d+ of ;.theanc,hon ofrFig. '1, resting on bottom prior to penetration anda-in the ing the flukes under a cable pull ata proper planing angle of 40 to 45 thereafter. Thus a cable pull on the opposite end of the shank and in the direction of shank extent will cause the fluke to progress into bottom along a plane substantially 40 to 45 to the line of cable pull. This means that the anchor including the shank may become completely buried in the ground, and that the shank may even be at an angle to the bottom plane, but as long as this latter angle does not exceed an angle placing the fluke in position to plane upwardly, the anchor will progress into the ground. When the shank is raised to an angle of 40 to 45 to the bottom plane, the fluke then j becomes parallel to the bottom plane and any increase in this shank-bottom angle will cause the fluke to rise toward the ground to meet the bottom level. Thus the anchor, merely by pulling on the shank at an upward angle to the shank,

may be made to plane out of the ground in order that itmay be quickly released or broken out of the bottom when desired. l

I have also .found that it is desirable to laterally extend the upper portions only of the fluke sections. These portions will act as a stock. All of the stock portion of a section is preferably in the same plane as the remainder of the fluke section and therefore aids in the planing action. Furthermore, I have found that when using a divided fluke anchor, with a central shank, that by hinging the fluke sections With relation to each other a dihedral angle can be maintained between them, this dihedral angle being highly efiicient in preventing the anchor from twisting, rotating, or cork-screwing out of the bottom, a common failing of prior anchors. I have found an efficient dihedral angle is a total angle of 30 from a straight line passing through theanchor crown, or for each fluke.

. Having described my invention broadly, other points will be brought out more in detail by di- I rect reference to the drawings. I

- 'Referring to Figs. 1, 2, and 3, a shank I preferably of cast steel or bronze-is provided at one end with a cable attachment 2, and at the-other end with a pin aperture carrying a hinge pin 3. Pin 3 is carried by-a yoke 4, this yoke being one end of a forged and machined taper pin 5.

Mounted ontaper pin 5, by-means of spaced hinge I lugs 6 and I, is a fluke section 8. 'Also mounted on taper pin 5 on hinge lugs 9 and I0 is an opposite fluke section II, lugs B and I and 9 and It) being offset and taper bored to fit alternately on pin 5, these sections being held thereon by end nut 12. The fluke sections are free to rotate on taper pin 5 within a predetermined range as will be explained later. The inner edge of each fluke section is provided with a tapering stiffenin rib l4 extending parallel to and closely adjacent shank I, and each fluke terminates in a penetrating point l5 at the end of stiffening rib I4 in order that a proper section engagement of relatively-hard bottom may be obtained. The forward edge of the fluke sections are preferably sharpened for best penetration.

Adjacent the crown of the anchor each fluke section is provided with oppositely disposed crown bosses l6 and I1, these bosses being close to lugs 6. 1, 9 and I0, and extending generally at right angles to the plane of the fluke sections. These bosses l6 and I1 arepreferably ofthinner sec- 'tion in the direction of ribs l4," and are opposed on-each side of each flukesection so that contact of the ends of either bosses l6 or bosses I! in'accordance with rotation of the fluke sections on pin 5 fixes the dihedral angle during the action of the anchor at approximately 15 for each fluke, as measured to a plane through the hinge line of the fluke hinge and disposed symmetrical to both fluke sections.

The top of each fluke section extends laterally to terminate in relatively narrow portions 20, coplanar with the remainder of the fluke, these extensions acting together to give a stock action to the-anchor inorder to insure that the anchor will lieflat on the bottom when thrown overboard from a vessel or vehicle.

Shank I is free to rotate on hinge pin 3 but is limited in the amount of rotation by shankend shoulders 2| on either side of pin 3, these shoulders oneither side coming to rest against flat surface 24 forming the bottom of yoke 4, and I prefer that the angle be close to the range of from 40 to 45 on either swing of the shank I, or to total swing.

Before proceeding with the description of the action of the anchor. in bottom, it is believed advisable to point out just why certain angle are desirable in the anchor of my .invention. I propose to discuss the anchor first as if the fluke were held in coplanar relationship so that the combined sections act as a single fluke, and in the same plane, thus eliminating any dihedral relationship. Under these conditions the most efficient planing and holding angle is obtained when the pull is applied to the fluke at or near the center of pressure, at an angle of 40 to 45. Ihe center of pressure is defined as being the point of application of all the actual pressure forces acting on the fiukesurfaces during penetration. At 45 approximately 70 per cent of the forward pull is translated into a downward moment along the plane of the fluke, and the area of the fluke, as projected along the line of pull, is sufficiently large to provide good holding power once the fluke is embedded. At lesser angles than 45 the downward progression is less even though the moment is greater. The projected area of the fluke in the direction of pull at angles less than 45 will, of course. be smaller. Theoretically, at angles larger'than 45 the percentage of forward pull translated into downward movement becomes less and less, although the effective areaof the fluke normal to the direction of pull becomes larger as the fluke approaches a 90 angle with the shank, at which point all downward moment would theoretically cease. ;'In practice the downward movement would cease before the 90 fluke shank angle is reached because the frictional component of the average bottom will prevent penetration if the angle of pull is substantially greater than 60. The basic reason that my anchor is able to plane into the bottom is that the fluke angle is such that the coefficient of friction does not prevent such planing, whereas in ordinary anchors, this coefficient of friction is opposed to planing action.

It is desired in the present anchor that the anchor shall at all times maintain an efficient planing angle. When the ,fiuke is buried and under a cable pull, it also is highly desirable that the shank be attached to the fluke adjacent the 'center of'pressure, and held with relation to the fluke at a planing angle as close to 45 as is pracnuke hinge line, it is advantageous to hinge the shank to the fluke with the effective center of pressure. between theshank-fiuke hingelline and the: fluke point, but with the efiective zcenter 'of pressure close to the hinge line, inforder that there may be slightly greater. pressureexertedv on the fluke pointside of the hinge line, than on the oppositeside of the hingeline, in order that the anchor may-never have any tendency to jackknife, or close up with the flukesections in the plane of the shank. From a practical .point of against the fluke in bottoms is not evenly dis- Weight operated tributed over the fluke area. anchor theory is based on the rough, and approximately correct, assumption that holding power varies directly with the depth of. penetration. This theory accounts for the factthat the holding power of weight type anchors varies approximately with weight for a given series of geometrically similar weight anchors. From a-prac t'ical standpoint therefore the pressure exerted on the fluke of the anchor of my invention during penetration would always be greater at thepoint of fiuke'than at the crown of the anchor, and this diiierential in pressure is suflicientl great to maintain the center of pressure belowthe hinge line even though the geometrical center of pressure calculated with uniform pressure over the entire fluke-may be located attimes at the crown side of the hinge line. All that is necessary therefore, is that the shank-fluke hinge line shall-be located adjacent the actual center'of pressure as developed in bottom, but-with the efiective center of pressure preferably located between the shank-fluke attachmentand the digging ends of the fluke section, irrespective of where the calculated, geometrical center of uniform pressure is, with respect to the shank-fluke hinge line. The center of area of the fluke sections need only be approximately determined, and can be readily found by inspection. As-the effective center of pressure is, when the anchor is buried, moved slightly toward the digging ends of the fluke sections from the center of area, as above explained, the approximate location of the effective center of pressure can also be determined by inspection.

In the design of my described anchor, or in the design of variations in fluke shape of my anchor, the fact that the anchondoes not jackknife, or close up the flukes parallel to the shank will of cours indicate that the actual center of pressure as the anchorisbeing used, is below the hinge line. I would also like to point out that icy-placing the actual shank-attachment'at a hinge line only slightly removedfromactual center of pressure as the anchor is being used, the stress on the shank is almost Whollytension; and that the bending moments existing in the anchor parts are small, and need only be sufficient to cause the fiukes to remain inplaning position with relation to the shank during use.-=

Thus the weight and bottom resistance of fluke arms. is eliminated and all structural weight "is concentrated in one useful fluke area and'in one. structural member which combines the function. of holding the fiukes at the proper angle to the line of pull, and connecting that line of pull to the flukes. Unlimited penetration is thereby accomplished.

One other feature is also important, which relates to the shank length, and with fluke length. When the anchor starts to penetrate into. the ground, resting on the fluke points and the cable attachment end of the shank, it is desirable that the angle of the fluke to bottom be not in excess of 60 in order that penetration may be readily started. As the frictional resistance to penetration at angles in excess of 60 increases so rapidly as to prevent proper penetration I thereforeprefer to adjust the shank length with relation-to fluke length to bring the anchor at or near that initial angle. In the anchor illustrated, the maximum fluke-shank angle is 40". A line drawn from the cable attachment end of the shank. to the center of pressure as found to exist in ordinary bottoms makes an angle with the fluk of thus placing the efiective pull exactlyon the center of pressure at that angle; and the line drawn from the cable attachment end of'the shank to the points of the fluke sections makes an angle with th fluke of approximately 56. This anchor has a ready initial penetration and-a continued planing action under a cable pull, with the desired bending moment necessary to keep' the flukes open.

The use of a dihedral angle in the composite fluke doe not change the relationships outlined above, as both fluke sections are planar. The

' dihedral reduces th efiective fluke section area normal to the line of cable pull slightly and this feature is utilized to stabilize the anchor. Thus, if the anchor tends to rotate,-the effective area of the rising fluke section normal to the line or" cable pull becomes greater and the area of the fallin one less, and the rising section thus oifer's more holding power than the opposite fluke section, thus counteracting the turning movement and returning the anchor to a central position, exactly as occurs in airplanes when a dihedral angle is used between two wing sections to stabilizethe machine.

Having thus described th structure of the anchor and pointed out the advantages of certain angular relationships of the parts thereof, I will now describe the action of the preferred form of anchor in bottom.

Referrin to the diagrams in Figs. 10 to l3,inelusive, and beginning with Fig. 10 showing the manner in which the anchor behaveson first reaching the bottom, the anchor may be provided with a cable 39 attached to the shank 2 0f the. anchor and the anchor thrown overboard to lie on bottom 31. The anchor will then assum the position shown in Figs. 10 and 14. Before any pull is applied, the points 55 of the flukes, the

ends of the stock portions of the flukes and the end of bosses H5 or ll will rest on bottom together with the end of the shank, irrespective of which side up the anchor happens to fall. As the pull is applied to the shank, in line-with the general direction of the shank, the ends/0f the bosses I 6 or ll penetrat the bottom to some extent "as do the ends of the stock portions, 28 and asthe anchor starts to move theyproducea pitching moment which throws points ifi-iinto bottom where. they. catch. The fluke; sections then hinge with respect to the shankaon thefiuke shank pivot 3 as shown in Fig. 11 until'the shank reaches its maximum permitted angle "to' the flukes. At this time the dihedral angle may also be present because the weight of the stock sections 20 may rotate fluke sections Band H on pivot 5. The anchor then planes into bottom as shown in Fig. 12. In this figure the shank is shown just ready to enter bottom with the ends of the stock portions 29 touching theground. The dihedral angle under the forward pull is now fully held at its maximum, and the rear bosses IE or I! as shown in Fig. are touching to maintain this angle. Under a continued forward pull the anchor continues to plane into the ground even though the shank may assume an angle with the bottom plane, and the fluke sections may become completely buried in theground. However, a stronger pull will force the fluke still further into the ground, and under an extremely heavy pull the entire anchor including the shank and stock portions of the fluke may become bur ied, thereby developing an exceptionally high holding power, the dihedral angle at all times protecting the anchor against rotation. As long as the shank does not exceed an angle of :45 with the bottom plane, there will be no tendency for the anchor to come out of the bottom. Thus, increase in forward pull creates downward movement of the anchor, and the resultant downward movement of the anchor increases its holding power. I have, for example, made experiments with a ten pound anchor wherein the shank and fluke sections are of cast steel, the flukes being of thin sections and of the same contour as shown in the drawings, with a shank-fluke angle of 40,

with a shank length sufiicient to give a 56angle with a line connecting the cable end of the shank with the points of the fluke, and found that this anchor will develop a holding power of in excess of 4,500 pounds. Repeated experiments have shown that a weight-to-holding-power ratio of at least 1:500 may be readily obtained. Increased holding power of my anchor may be attributed to efficient distribution of weight and unlimited penetrating power due to the fact that the fluke is maintained at all times after penetration at an efiicient planing angle.

In Figs. 5 to 8, inclusive, I have shown various modifications of fluke shape which may be used in conjunction with the anchor of my invention. The fundamental basis of all of these shapes is that the digging end of the fluke shall be relatively sharp-pointed with a gradual increase in width, the fluke section having its maximum width at the crown end. There will be some variation in the positions of the effective centers of pressure when using fluke sections of different contour, as it will be obvious that different fluke section shapes may shift the center of pressure slightly toward or away from the crown of the anchor. Such a shift in the effective center of pressure, however, is not important unless the shift would bring the hinge line of the shank on the point side of the effective center of pressure in which case the anchor would of course will be obvious from an inspection of Figs. 5 to 9,

inclusive, that certain of these anchors have greater actual fluke section area than others and this change in area may be very effectively utilized for anchors designed for special purposes. For example,'an anchor with the fluke section shape of Fig. 6 may be utilized in relatively hard bottom with good penetration and consequent good holding power, wherein a fluke section shape such as shown in Fig. 9, may be utilized in relatively soft muddy bottom in order to give greater holding power and greater planing ability.

The shapes shown in Figs. 7 and 8 are intermediate in area between the sections shown in Figs. 8 and 9. The type of fluke area shown in Fig. 5 may be utilized when it is advisable to use a. relatively short effective stock, and where it is desirable that the effective center of pressure be well toward the points of the fluke sections. The features common to all the shapes shown are that the points of the fluke sections are sharpened and closely adjacent the shank plane, that the opposite edges of the fluke section are extended laterally to insure the anchor lying flat on bottom, and that the effective center of pressure of the combined fluke sections be kept relatively close to and preferably on the point side of the shank hinge line.

I do not therefore wish to be limited to any particular fluke section shape as it will be obvious to those skilled in the art that by following the teachings given herein, almost innumerable fluke shapes will be satisfactory for various purposes as desired. In that regard I have found that the shape shown in the anchor of Figs. 1 to 3, inclusive, is a satisfactory compromise for use in hard, medium, and soft bottoms. The fluke section shape has the sharp points for initial penetration, relatively slow flaring of the fluke section near the point, with the gradual lateral extension of the sides of the fluke sections into the stock portions 20. Such an arrangement places the larger part of the actual area of the fluke lose to the shank plane with the effective center of pressure close to the hinge line to keep the fiukes open under all circumstances.

It is to be noted that all parts of my anchor are designed to facilitate complete penetration beneath the bottom plane. The flukes are of thin section and present little resistance to the bottom material. Crown bosses l6 and I! are streamlined in the direction of penetration to reduce penetration resistance, and the entire stock surface opposed to bottom is reduced to the minimum. Thus the anchor planes readily into and beneath the bottom without resistance which would be caused by extended surfaces opposed to the line of penetration movement.

I claim:

1. An anchor comprising a shank, a cable attachment at one end of said shank, and a fluke having a digging end-and an opposite end, said shank bein attached to said fluke intermediate the ends thereof at a point closely adjacent the effective center of pressure developed on said fluke by a cable pull through said shank, when said fluke is completely buried in penetrable bottom, with a fluke-shank angle of approximately 40 to 45, portions of said fluke being extended laterally on the opposite side of the shank. attachment from the digging end of said fluke along substantially a smooth curve, to form an effective stock.

2. An anchor comprising a pair of substantially planar fluke sections having adjacent long dimensions and outwardly flaring edges, said sections when combined forming a symmetrical split fluke. a hinge pin extending between the adjacent edges of said fluke sections adjacent the wider portions thereof, hinge bearings on each of said sections and engaged by said hinge pin, means for limiting the rotation of said fluke sections relative to each other around said pin as an axis, a shank rotatively connected to the lower end of said hinge pin, and means for limiting the rotation of said shank with respect to said hinge pin.

3. An anchor comprising a shank, a fluke section attached on each side of said shank, with a rotation stabilizing dihedral angle of approximately of said fluke sections under a cable pull.

4. An anchor comprising a pair of fluke sections having adjacent edges and connected between said adjacent edges by a hinge, a shank attached to both of said sections on the line of said hinge, and cooperating stop means limiting the relative movement of said fluke sections to a rotation stabilizing dihedral angle for each section as measured to a plane through the line of said hinge and disposed symmetrical to said fluke sections.

5. An anchor comprising a pair of fluke sections having adjacent edges and connected between said adjacent edges by a hinge, a shank attached to both of said sections on the line of said hinge, and cooperating stop means limiting the relative movement of said fluke sections to a rotation stabilizing dihedral angle of approximately 15 for each section as measured to aplane through the hinge line of said hinge and disposed symmetrical to said fluke sections.

6. An anchor comprising a pair of fluke sections having adjacent edges and connected between said adjacent edges by a hinge, a shank attached to both of said sections by a second hinge on the line of said first hinge, cooperating stop means limiting relative movement of said fluke sections to a symmetrical dihedral angle of approximately 15 for each section as measured to a plane through the hinge line of said hinge and disposed symmetrical to said fluke sections, and additional stop means cooperating with said shank and fluke sections to limit rotation of said fluke sections on said second hinge to 40-45 on either side of said shank.

7. An anchor comprising a pair of fluke sections having adjacent edges, having hinge bearings mounted thereon, a hinge pin passing through said hinge portions hingedly connecting said fluke sections, stop means limiting rotation of said fluke sections on said hinge pin to opposite and equal dihedral angles on each side of a commonfluke section-hinge pin plane, a shank having a cable attachment at one end thereof, a second hinge joining said hinge pin and the other end of said shank intermediate the, extent of the adjacent edges of said fluke sections, and additional stop means limiting relative rotation of said hinge pin and said shank to equal angles on each side of the coextensive position thereof.

8. An anchor in accordance with claim 7 wherein said stop means are respectively proportioned to hold said anchor when embedded with said fluke sections at a dihedral angle of approximately 15, and with said hinge pin at an angle to said shank of from 40 to 45.

9. An anchor in accord'ancewith claim 7 wherein said fluke sections are provided with digging ends and wherein the ends of said fluke sections on the opposite side of said hinge pin-shank attachment are extended laterally in the general plane of each fluke section to act as stock portions.

10. An anchor comprising a shank, a cable attachment at one end of said shank, a fluke section on each sideof said shank, said fluke sections being connected together and to the other end of said shank, said shank connection being adjacent the effective center of pressure as developed on the combined area of both of said sections under a cable pull when buried in penetrable bottom, means for holding said fluke sections at an angle of approximately to to the shank when so buried, said fluke sections being connected to gether by a hinge, and means for limiting the relative rotation of said fluke sections on said hinge to provide a rotation stabilizing dihedral angle on said fluke sections when under said cable pull in bottom.

11. An anchor comprising a shank, a cable attachment at one end of said shank, a fluke section on each side of said shank, said fluke sections being hingedly connected togetherand to the other end of said shank, said shank connection being adjacent the effective center of pressure as developed on the combined area of both of said sections when buried in penetrable bottom, and means for limiting the relative rotation of said fluke sections on said hinge to provide a rotation stabilizing dihedral angle on said fluke sections of approximately 15 when under cable pull.

12. An anchor comprising a shank, an extension hingedly secured at one end of said shank,

and afluke hingedly secured to said extension for movement normal to the movement of said shank. 13. An anchor comprising a shank, an extension hingedly secured at one end of said shank, a pair,

side of said common plane, and meansfor limiting the hinge movement of each fluke to a predetermined angle on either side of said common plane.

14. An anchor in accordance with, claim 2 wherein said fluke section limiting means limits the relative rotation of the two fluke sections to substantially 60 and wherein said shank limiting means limits said shank rotation with respect to said hinge pin to approximately 40 to 45 on each side of said shank.

15. An anchor inaccordance with claim 2 wherein said fluke section limiting means limits the relative rotation of the two fluke sections to substantially 60 and wherein said shank limiting means limits said shank rotation with respect to said hinge pin to approximately 40 to 45 on each side of said shank, and wherein the length of said fluke sections and the length of said shank are coordinated to provide an initial fluke penetration angle of approximately 60 under a cable ull. p JOHN K. NORTHROP.

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