US2643631A - Anchor - Google Patents

Description

June so, 1953 R. s. DA FQRTQ 2',s43,s31

ANCHOR Filed Sept. 10, 1946 4 sheets-shat 1 K Shank eng/h l2 l D A Fluke any 3 T 22 Af/ack an 9/e5 Poin/ angle U F l E J- F I E E GED/Er 0/ 1 /111: fbrwara' face. 2

l5 /6 I r F; IE El R I Z/- INVENTQR Richard .51 Danforfh ,6 ATTOR N EY June 30, 1953 R. s. DANFORTH 2,643,631

ANCHOR Filed Sept. 10, 1946 4 Sheets-Sheet 2 INVENTOE P/charoS. Danfor-fh ATTORNEY 30, 1953 R. s. bANFORTH v2,643,531

ANCHOR 4 Sheets-Sheet 3 Filed Sept 10, 1946 INVENTOR P/chardi Danfor/h ATTO RN EY June 30, 1953 R, s; DANFQRTH 2,643,631

ANCHOR Filed Sept. 10, 1946 4 Sheets-Sheet 4 IN POUNDS WEIGHT OF ANCHOR Patented June 30, 1953 ANCHOR Richard S. Danforth, Berkeley, Calif., assignor to Robert H. Eckhoif,

Piedmont, Califl, as trustee Application September 10, 1946, Serial N 0. 696,001

9 Claims. (Cl. 114208) This invention relates to an improved anchor of the type shown in my Patents 2,249,546 of July 15, 1941, and 2,320,966 of June 1, 1943. Such an anchor generally includes a shank with twin nukes generally mounted at one end of the 'shank and arranged to swing through a limited angle on either side of the shank. A stock is usually provided at either the forward end of the shank or at the after end of the anchor.

As compared to anchors known theretofore,

the anchors manufactured in accordance with my aforementioned patents provided vastly increased holding power as well as many operational advantages and improvements. For example, as is reported in Patent 2,249,546, a 29 lb. anchor of the construction disclosed in that patent held in excess of 6,000 lbs. in hard sand, or better than 290 lbs. per pound of anchor weight as compared to 2 lbs. per pound of anchor weight for a conventional stockless anchor in the same bottom; in addition, my anchor engaged bottom readily when a pull was applied, the anchor assuming its proper operational position so that continued pull urged the anchor downwardly until the anchor was firmly engaged and remained practically stationary against further pull; the anchor did not rotate under continued pull, that is, it was stable and continued its engagement, as compared to prior anchor structures of the same general type which frequently turned repeatedly about the shank as a central axis until finally the anchor freed itself from engagement with the bottom.

The principal load carrying members of an anchor are the shank and the fluke arm; both these may be likened in stress to the action of a cantilever beam. It has been heretofore established that the holding forces of similar anchors similarly disposed to the surface of a given sea bed are in proportionto the cubes of the characteristic lineal dimensions of the anchors such as the shank length. It should be understood, however, that there are many variable features in anchor design which may affect the penetration of an anchor and thereby affect materially the holding power.

The engineering design of a cantilever beam such as the shank or fluke arm is based upon the bending moment at any given section in comparison with the section modulus at the same point. The bending moment in turn is dependent upon the load applied to the anchor multiplied by the arm of application of this load. As the load applied to the anchor is proportional to the cube of a characteristic lineal dimension and the arm is directly proportional to a lineal dimension, the bending moment on the cantilever beam is proportional to the 4th power of a char acteristic lineal dimension, such as the length of the shank or fluke arm. The section modulus varies as the cube of a characteristic cross sectional dimension. The cross sectional. dimensions of the portions of an anchor acting as a cantilever beam should therefore vary as the $4; power of a characteristic lineal dimension in order to provide uniform stress in the metal as the size of the anchor is varied.

As a result of the cross sectional dimensions varying as the 7% power of a characteristic lineal dimension, the weight of the portions of an anchor so designed for uniform strength vary as the power of a characteristic lineal dimension such as the shank length, or as the power of the load. As a result of this variation in similar anchors of uniform strength, the larger the anchor and the greater the weight, the less is the ratio of unit holding'power to unit weight. These relations do not apply to geometrically similar anchors of different weights for these will not have uniform strength.

In my prior Patent 2,249,546, I have pointed out that an anchor of the type with which this invention is concerned should include various of the following factors in combination to ensure attainment of the operational characteristics essential to a reliable anchor of good holding power.

' A. The fluke area should be not less than 0.4

the resistance area. Preferably it should be not less than 0.6 and even more preferably it should be greater than the resistance area.

B. The resistance area should be less than 25% of the square of the shank length, pref-' erably less than 13%, and more preferably less than 10% of the square of the shank length.

0. The point angle should be less than 75 and preferably less than 70.

D. If 35% or more of the fiukearea is aft of the pivot point the-attack angle should be in the range of 30-50; if less 'than'35% is aft of the pivot point, that is more than 65% of the fluke area is forward of the pivot point, the attack angle should be in the range of 4060.

E. The stock length should be at least twice the distance between the respective centers of area of the fluke and preferably two and onehalf or three times this distance.

In that patent I also emphasized my finding that it was necessary to coordinate the resistance area with other anchor characteristics such I as the fluke area. While these and other terms are fully defined in that patent, for convenience, I will presently define these and other characteristics. For the present, it can be pointed out that the ability of an anchor to dig in and penetrate bottom until the anchor is securely buried in the bottom is dependent upon the resistance of the anchor to burial; the driving force applied to the fiukes under continued pull on the shank must be sufficient to cause the anchor to make the desired penetration into the bottom.

In constructing similar anchors of uniform strength but of different weights in accordance with my patents, I observed that the holding power of each anchor per pound of weight decreased as the weight of the anchor increased even though the other operational advantages remained. This is attributable to the previouslymentioned fact, that is, as characteristic lineal dimensions are increased to produce a similar anchor of uniform strength but of greater weight, the weight of the principal load carrying members increases as the power of any of such characteristic lineal dimension; in similar anchors of uniform strength but of different weights, the heavier the anchor the less is the unit holding power per unit of weight. I have now discovered that the resistance area of an anchor is not the only factor to be considered in constructing an anchor'to have a high holding power per pound of weight and that one should consider additionally and give attention to the resistance to burial of those portions of the flukes which are effective to cause the anchor to dig in to bottom and penetrate bottom continuously. The portions of the flukes which are effective to cause the anchor to dig in and penetrate bottom are generally those which are forward of the pivotal mounting of the flukes on the shank. Since it is usual in anchors of the type with which this invention is concerned to provide a crown structure at the after end of the anchor to ensure that the flukes will engage bottom promptly when the anchor is dragged along the bottom and since the crown provides additional resistance, it is preferable to consider only those fluke portions which are forward of any substantial portion of the crown. Because the forward extension of the crown may vary, I have found it more reliable to consider only those fluke portions which are forward of the pivot at least one-fifth (20%) of the length of the shank.

To ensure attainment of the maximum holding power by an anchor of a given weight and to coordinate the driving force of the flukes with the resistance of the flukes to burial I have found that (a) the projected cross sectional area of the fiukes measuredon a plane passed through the fiukes at a distance forward of the pivot oneflfth the shank length and normal to the longitudinal axis of the fiukes (hereinafter termed the fluke resistance area and further defined in detail) should bear a relationship to (b) the area of those portions of the nukes and the fluke arms which are forward of the fluke pivot mounting at least one-fifth of the shank length (herein after collectively termed the fluke forward faces) and (c) to the weight of the anchor.

Stated concisely, I have found that the area of the fluke forward faces and the fluke resistance area should have a certain relationship and that this can be coordinated with the weight of the v anchor. I have determined that when the aforementioned; areas are measured in square inches and the anchor weight is -taken in pounds (W) Fluke resistance area 0.133 Area fluke forward faces ololoW. (mmlmum) Fluke resistance area Q 0.1363 Area fluke forward faces OOIQW (pleferred) Fluke resistance area I Area fluke forward faces (maxlmum) If these'ratios are observed, then the fluke resistance area, the area of the fluke forward faces and the Weight of the anchor can be successfully coordinated and one can secure the maximum operational holding power consistent with the strength of the anchor.

It is the generally broad object of the present invention to provide an improved anchor structure wherein the desired characteristics of assured deep burial under continued pull is present, the maximum holding power is attained and the anchor is free from such disadvantages as furrowing, skidding and rotation, and the anchor is uniformly stressed with variations of weight and size.

The usual method of constructing anchors of the type with which the present invention is concerned has been to form the several major parts, that is the stock, shank and flukes, by

- casting these in suitable molds in accordance with usual foundry practice. This type of construction, while satisfactory, is relatively slow and is comparatively expensive. Another alternative is to form the several parts as by forging, rolling or stamping, subsequently welding or riveting the individual component elements together. While this type of construction is generally more. rapid than the usual foundry practice, it is relatively expensive and is not suited to the production of a relatively great number of anchors at low unit cost. I have now found that it is possible to form the anchor of standard metal structural elements or from metal sheets, particularly the fluke portions of the anchor so that a complete anchor can be readily assembled by a few relatively simple welding operations.

Another object of the present invention is to provide an anchor construction in which major components of the anchor can be formed from readilyavailable structural steel elements.

The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter wherein thepresent preferred form of anchor construction is set forth.

In the drawings accompanying and forming a part hereof,

Figure 1 is a side elevation of an anchor embodying the present invention .with the flukes in one operational position with respect to the shank.

Figure 2 is a plan view of the anchor as shown in Figure 1.

Figure. 3 is an end view looking at the ends of the flukes with the shank in an operational position.

Figure 4 is a plan view of the anchor shown in Figures 1-3 with the fiukesand shank extending parallel to one another.

Figure 5 isa side elevation, partly in section,

aeeaesr Figure 6 is a section taken along the line 66 in Figure 5 and illustrating the construction-ofthe crown of the anchor.

Figure 7 is a rear elevation of the crown portion of the anchor.

Figure 8 is a section along the line 8-8 in Figure 4.

Figure 9 is a diagrammatic view showing one of the methods used in fabrication of the nukes.

Figure 10 is a plan view illustrating one step in the manufacture of the flukes.

Figure 11 is a plan view of a modified form of anchor.

Figure 12 is a view along the line l2-l2 in Figure 11. s

Figure 13 is a graph showing the ratio of the fluke resistance area to the area of the fluke forward faces wherein curve A corresponds to the value 0.010 W and curve B corresponds to the value of the formula 0.27 Vi for a given weight of anchor, in pounds.

The anchor shown in Figures 18 comprises a shank ii a twin fluke unit 9 comprising the crown generally indicated at l2, fluke arms H and nukes It and a stock [3 which provides a hinge mounting for the twin fluke unit 9 at the after end of the shank. The forward end of the shank is provided with an elongated aperture it so the eye end of a shackle can be inserted and the shackle pin inserted in the shackle eye-ends to join the shank directly to a chain link. By constructing the shank end with such an opening one less shackle is required as compared to the usual practice.

The shank is preferably tapered longitudinally, as is shown in Figure 1, to provide the maximum strength at the after end where the greatest strength is required. The shank is also tapered on its transverse axis to permit it to enter and pass through bottom with a minimum of resistance. The shank has an aperture at its after end as do the fluke arms ll through which stock 53 is passed to hinge the fluke unit S on the shank end. In the form of anchor shown in Figures 1-8, thestook is preferably tubular and is open throughout its length to lighten this por-- tion of the anchor.

The crown i2 is provided by two plates [5 each cut away as at 23 to provide two legs ll which extend on either side of the fiukes to provide a passage in which the shank can swing, the swing of the shank flukes on the stock being limited by stops it which are welded to fluke arms H and, in the larger anchors, to each of the plates E5. In the form of anchor shown in Figures 1-8 in position by-a weld made between each fluke rear edge and the stock adjacent the outside edge of each fluke. The stock, in this form ofanchor, is preferably made of a length of tubing to reduce the weight at'the rear end of the anchor.

In accordance with this invention, the twin fiukes unit 9 utilized 7 in the anchor shown in Figures 1, 2 and 3 is provided by cutting the unit from anI-beam 3| (Figure 9) having flanges 32 joined by a web 33 as appears in Figure 9 wherein I have shown diagrammatically two fluke units 9 laid out on a length of the beam. The beam can be a standard structural element having two flanges joined by a web or a T or similar section or one specially rolled to provide a section of the desired shape and material. By utilizing such an element, one is able to fabricate the fluke unit by suitable cutting operation and to form the unit from a metal of suitable strength to provide a structure having a desired strength per unit of weight. Depending on the size of the fluke unit, one can achieve various lay-outs. of the fluke unit on. the structural element employed, a typical lay-out being that previously referred to and shown in Figure 9; In the larger size anchors, the width of web portion 3 1 usually does not admit of the lay-out of two fluke units opposite one another as I have shown in Figure 9 and it is necessary to stagger the fluke units with the angular edge of a fluke in one unit falling against an edge of a fluke in another unit. The web portion 34 is cut away and the flange is bent as at 35 so that the fiukes are in the same plane and extend in the same direction from the bent portion 38. The flanges 32 are preferably tapered as appears in Figure 1 toward the fluke points and the edges of the fiukes are sharpened so the flukes easily penetrate bottom.

In that form of anchor shown in Figures 11 and 12, the stock is provided by a length of rod or tubing and the flukes are fashioned by cutting from a plate and forming a rib 4! on each of the fiukes in a brake or other sheet metal Working device. Therib is formed on only one side of each fluke (Figure 11) so that a fluke can be used for only a right hand or a left hand fluke, as the case may be. Because of this, the two ribs in each anchor extend in the same directions but on only one side of the flukes. With this construction, equal resistance to burial is provided by each fluke in either operational position. This type of fluke is especially suitable for use in relatively light weight anchors since relatively light each fluke arm is formed with a recess ISA in which the forward end of each stop fits. Each of the plates includes a portion 49 sloping upwardly and rearwardly from the fiukes at an angle between .26 and 45 and terminating in a substantially fiat portion 2t which is substantially para lel to the flukes as is disclosed in my Patent 2,3u-i,666. An aperture 25 is provided in each of the plates 55 adjacent the junction of portions iii and crown to burial.

To support plates H5 in a spaced relation to one another and to the stock, spacers 22 positioned between the plates and feet 22A are welded to each of the plates (Figures 7 and 8). The spacers and fluke arms each have an aperture through which the stock is passed, and in which it is supported (Fig. 6). The stock is retained all to reduce the resistance of the sheet metal plates can be utilized to form the several parts which can be'joined by spot welding. The crown construction utilized is like that previously described except that stops it are omitted, the swing of the shank relative to the fiukes being limited by the aperture 23 formed in each plate It. a

Both forms of anchors are characterized by a relatively high strength and simplicity in the manufacturing operations, a few simple welds sufficing to'join the several parts together. For example, the stock is inserted in place and welds are then made between the .rear edges of the ilukes and the stock as at 32 to secure the stock in place; 'With the stock supported in the crown and joined to the fluke edges, "each projecting unsupported end of the stock becomes a short cantilever beam of relatively great strength. This enables a lighter stock to .be utilized.

The various anchor and dimensional relations which l have found to be essential toor desirable for the production of high holding power coupled 7 with reliability and the terms which I have utilized heretofore or to which I will make further reference are as follows:

Referring to Figures 1--3, A is the point of the cable attachment; B is the axis or the pivot, in this case the center line of stock 13; the line B-B is the axis of the stock; the line -D is the axis of the shank. 7 v

The line E -F lies in a plane coinciding with the advancing faces of the flukes. The points H H are the points or forward ends of thefiiik'es.

The effective shank length is the distance A-B from the point A of cable attachment to the axis of the pivot '3; it is indicated by the dimension and is referred to herein as the shank length. The measurement M is the dlstance between the pivot axis BB and the mike poi'nts and is referred to herein as the over-all fluke length. The measurement N, as shown in Figure l, is a distance from the axis of the pivot, along the axis of the fluke, equal to of the shank length. in the claims, where reference is made to this measurement, it is of course to be made along the fluke axis.

The measurement 0 is the length of that ortion of the crown which extends rearwardly in a plane approximately parallel to that of the nukes.

The measurement P between the centers of area G'G of the entire face area of the cares and fluke arms is termed the fluke center "spacing; the centers G-G can be located by usual and known geometrical methods.

The measurement Q (Figure 6) is the distance taken along the stock b tween the longitiidinal axis of the shank and that point whereat line Q'Q', projecting a substantial portion of the inside edge of the fluke, intersects the center line is -3' of the'st'ock. I I

The measurement R is the over-all length of the stock.

The angle S between the plane of the fluke forward faces and a plane passedthrough the point ofcable attachment A and the centers of areas Ki-K' of the fluke forward faces (these centers being located as hereinafter described) is termed the attack angle;

The angle T between the filament the fluke forward faces and the axis of the shank is termed. the fluke angle. n

The angle U between the plane of the fluke forward faces and a plane passed through cable attachment point A and the points or forward ends H-H of the flukes is termed the point angle.

The angle V is the fluke directional angle, between the axis of the shank (Figure 2) and a straight line approximating the inner edge of the fluke.

The angle X is the fluke point angle, between the inner and outer forward ed es of the fluke. This angle ls preferably from 2:1" to 27.

The angle Y is the crown an le (Figure 1) taken between the crown face and the fiilke'axis.

The resistance area is the total sectional area of the anchor projected parallel to'the fluke axis with the flukes open, the projection being made onto a plane normal to this axis. It can be visualized as the shadow cast on level ground by the sun in zenith when the anchor in operational position (the nukes open) is held with the fiukes pointing directly toward the and is represented by the entire area in Figure 3.

The fluke area" is the sum of the areas of the entire front face'sof the two nukes.

8 The fluke forward faces comprise those portions of the nukes forward of the stock a distance greater than 20% of the shank length, the area tional area of the fiukes projected from a point spaced an infinite distance in advance of the fluke points H onto the plane I-J and measured in square inches.

The weight, W, of the anchor is the weight of Q the complete anchor in pounds. The ratio of the fluke resistance area to the area of the fluke forward faces, for a given weight of anchor, is shown in Figure 13, wherein curve B corresponds to the ratio for a given weight determined by the formula O.027W- while curve 'B corresponds to the ratio for a given weight of anchor determined by the formula 0.010W- While the weights run only between one and one hund'red thousand pounds, the curves can be extended as straight lines to include smaller or larger weights of anchors.

When an anchor is dragged over the bottom it is essential that the flukes move immediately into position to engage and bury in the bottom. A common failing of many anchors is that of skidding, i. e. the flukes remain in or are elevated above the plane of the shank as the anchor is dragged along the bottom. This failing is particularly evident when the bottom is soft mud. To reduce the tendency to skid, I have found attention should be given to several structural components, the length of the after portion of the crown (measurement 0), the spacing of the flukes with respect to the shank and the fluke directional angle (angle V). These will be discussed in the order in which they have been named.

The length of the after portion of the crown which extends generally parallel to the flukes should be at least 6% of the shank length, that is, dimension 0 should be at least 6% of dimension K. Preferably, the after crown portion should have a length of 8%10% of the shank length. By lengtheningthis portion of the crown, the tendency to skid is reduced. In prior anchors (such as that shown in my Patent 2,354,666) this element has been relatively short, usually about 2% or" the shank length.

skidding is also affected by the spacing of the 'fiuke arms from the shank. I have found that the skidding tendency can be reduced by spacing the fluke arms from the shank and flaring the fluke arm inner edge outwardly with respect to the shank. The fluke arm inner edge can be straight or curved; according to my investigamom, a straight line approximating the fluke arm inner edge (Q' Q') should, when projected, intersect the center line of the stock (B'-B') at a point spaced from the center line of the shank a distance equal to 1.5% to 3% of the shank length. In Figure 6, I have shown this distance as the dimension Q; reliable performance has been secured when this distance, dimension Q, is

2.25% of the shank length. In addition, a line approximating the fiuke arm inner edge should make an angle of approximately 4 with the shank center line; this is angle v, the fluke direcfluke arms is then approximately 8.

The distance between the fluke arms is generally between 3% and 6% of the shank length with the preferred spacing equivalent to 4.50% of the shank length. The radius of curvature of portion 36 (Figure 10) should be such as to ensure thi spacing.

The utility and advantage of the present invention is illustrated by comparing the holding power of an anchor constructed in accordance with my prior Patent 2,249,546 and one constructed in accordance with this invention; A thirty pound anchor embodying the several structural features and relationships of my patent was chosen for comparison with a seventeen pound anchor of the present invention because the principal anchor components were of approximately the same size;; Testing the two anchors underthe same conditions and on the same bottom resulted in the thirty pound anchor resisting a pull of 6,000 pounds hile the seventeen pound anchor resisted a pull of 9,000 pounds. On a per pound basis the thirty poundanchor held 200 pound per pound while the seventeen pound anchor held 530 pounds.

I claim:

1. An anchor of the twin fluke type comprising a shank having a forward and an after end with 'a cable attachment at its forward end; a pair of flukes; a crown at the after end of said fiukes comprising two plates, each of said plates sloping upwardly and rearwardly from the fluke faces to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the flukes; spacers joining the plate portions together; and a stock mounted in said spacers and joined to the pair of nukes and pivotally mounting said flukes at the after end of said shank with the fiukes extending forwardly from the stock.

2. An anchor of the twin fluke type comprising a shank having a forward and an after end with a cable attachment at its forward end; a pair of nukes; a crown at the after end of said fiukes comprising two plates, each of said plates being joined to said nukes at the forward end of the plate and sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the flukes; spacers joining the plate portions together; and a stock mounted in said spacers and joined to the pair of flukes and pivotally mounting said fiukes at the after end of said shank with the flukes extending forwardly from the stock.

3. An anchor of the twin fluke type comprising a shank having a forward and an after end with a cable attachment at its forward end; a pair of flukes each supported on a fluke arm; a crown at the after end of said flukes comprising two plates, each of said plates being apertured to permit said shank to swing with respect to said flukes and provide a stop for such swinging movement, each of said plates sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and sub stantially parallel to the plane of the fiukes; spacers joining the plate portions and fluke arms together to support the same; and a stock mounted in said spacers and in said fluke arms and pivotally mounting said fiukes at the after end of said shank with the flukes extending forwardly from the stock,

"4. anchor of the twin fluke type comprising a shank having a forward and an after end with a cable attachment at its forward end; a pair of substantially like flukes, each fluke having an arm along theinner edge thereof extending beyond the rear edge of the fluke and joined to the arm of the other fluke; a crown at the after end of said flukes comprising two plates, each of said plates being joined to said fiukes at the forward end of the plate and sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the fiukes; spacers joining the plate portionsand said arms together; and a stock mounted in said spacers and in said fluke arms and pivotally mounting said flukes at the after end of said shank with the fiukes extending forwardly from the stock.

5. An anchor ofthe twin fluke type comprising a shank having a forward end; a pair of substantially like flukes, each fluke having an arm along the inner edge thereof extending beyond the rear edge of the fluke and-joined to the arm of the other fluke; a crown at the after end of said flukes comprising two plates, each of said plates being apertured to permit said shank to swing with respect to said nukes; a stop secured to each fluke arm to limit such swinging movement of the" shank; each of said plates being joined to said flukes at the forward end of the plate and sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the flukes; spacers joining the plate portions and arm together; and a stock mounted in said spacers and fluke arms and joined to the rear ends of said flukes and pivotally mounting said flukes at the after end of said shank with the flukes extending forwardly from the stock.

6. An anchor of the twin fluke type comprising a shank having a forward and an after end with a cable attachment at its forward end; a pair of nukes, each fluke having the inner edge thereof bent to project outwardly from one face of each fluke; a crown at the after end of said flukes comprising two plates, each of said plates being joined to said flukes at the forward end of the plate and sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the flukes, each of said plates being apertured cooperatively adjacent the shank to provide a stop for limiting the relative movement of the flukes and shank; spacers joining the plate portions and said arms together; and a stock mounted in said spacers and in said fluke arms and pivotally mounting said fiukes-at the after end of said shank with the fiukes extending forwardly from the stock.

7. An anchor of the twin fluke type comprising a shank having a forward and an after end with a cable attachment at its forward end; a pair of flukes, each fluke having an arm along the inner edge thereof extending along and projecting outwardly from only one face of each fluke; a crown at the after end of said flukes comprising two plates, each of said plates being joined to said flukes at the forward end of the plate and sloping upwardly and rearwardly to terminate in a plate portion extending rearwardly beyond the flukes and substantially parallel to the plane of the flukes; spacers joining the plate portions and. said arms together; and a stock mounted in said spacers and in said fluke arm and pivotally mounting said flukes at the after end of said 11 shank with the fiukes extending forwardly from the stock.

8. An anchor comprising a pair of fiukes lying generally in a, common plane, .for pivotal movement between said .flukes about an axis to, the rear of said fiukes, a pair of .thin, fiat crown plates, each plate having an opening therein to admit the shank and being joined to both' flukes "on each side of the shankopening andhaving one thin, flat portion sloping rearwardlyv away from the fiukes to a second thin, fiat portion extending rearwardly from the first portion and substantially parallel and in a spaced relation to the fiukes and to the second portion on the other crown plate, and astop secured on the underside of each first plate portion .on each side .of said opening between onesideof the fiukes and the second portion of .the crown. plate and including a transversemember inclined rearwardlytoward the plane of said flukes for engagement with the shank.

9. ..An anchor comprising a pair of fluke blades lying generally. in a common plane, a flange on the inner edge of .each blade projecting at right .angles from at least one .face of said blade, a pair of thin, flat crown plates each, having an opening therein and being joined to both flukes on each side of the opening and having one thin, flat portion sloping rearwardly away from the .flukes tow a second thin,..flat. portion extending rearwardly from theffirs't portion substantially parallel and in a spacedrelation to the flukes and to the second portion. .on the other crown plate, a stop including a transverse member inclined rearwardly toward the plane of said blades, a pair of spacers each secured to one of the flanges and to the. second portion on each plate, and a shank engageable with said stops and mounted for pivotal movement between said flanges about an axis to therear of said stops and between said stops.

. RICHARD S. vDANFORTH.

References Cited 'lnthe file of this patent UNITED. STATES PATENTS Number Name Date 503,591 Fisher Aug. 22, 1893 527,060 House Oct. 9, 1894 532,184 Rettig Jan. 8, 1895 670,368 Byers Mar. 19, 1901 814,229 McGillivaryet a1. Mar. 6, 1906 1,329,563 Upson Feb. 3, 1920 1,331,095 Curry Feb. 17, 1920 1,373,741 Jones Apr. 5, 1921 1,562,746 Eells Nov. 24, 1925 2,249,546 Danforth July 15, 1941 72,282,566 Danforth May 12, 1942

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