US3015299A - Mooring anchor - Google Patents

Description

Jan. 2, 1962 R. c. TOWNE ETAL 3,015,299

MOORING ANCHOR Filed Dec. 23, 1959 2 Sheets-Sheet 1 INVENTORS 42 RICHARD C. 75w:

y JOHNNIE V. STALcuP MAW ATTORNEY Fls.3. 4/

Jan. 2, 1962 R. c. TOWNE ETIAL 3,015,299

' MOORING ANCHOR Filed Dec. 23, 1959 2 Sheets-Sheet 2 INVENTORS RICHARD c.7aW/VS BY JoH/wv/E V. STALcUP A roe/var United States Patent Qfitiee Fatented Jan. 2, 1962 3,015,299 MOORING ANCHOR Richard C. Towne, 822 N. Roderick Ave., Oxnard, Caiii, gohnnie V. Stalcup, 533 Acacia Road, Santa Paula,

Filed Dec. 23, 1959, Ser. No. 861,725 3 Claims. (Cl. 114-203) (Granted under Title 35, US. Code (E52) sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to anchors and particularly to those types that are especially designed for use as stable mooring devices for anchoring large marine structures permanently in place.

The use of various types of ship anchors for the mooring of large floating structures such as drydocks, cranes, large work platforms, and similar equipment has been found unsatisfactory with the increase in size of such floating structures. Such disadvantages of the ship anchors have resulted from their essential design. These types of anchors are used intermittently and are designed to develop a quick holding power with comparative ease of removal from the ground. In order to compensate for the removable feature, ship anchors are required to depend upon comparatively massive construction and weight. Many times, the weight of the anchor and its chain cable are sufficient to moor a vessel for the usual short time.

In the studies, tests, and experimentation performed in the selection and design of a suitable heavy-duty mooring anchor, all types of anchors were used including those designed particularly for this purpose. The design criteria for such a mooring anchor as determined from this investigation include the following:

(a) Light in Weight; fabricated from steel plate.

(b) Two flukes which can rotate to at least a 50 angle from the shank. Fluke area to be dependent upon the required holding power. Length and width of the flukes to be proportioned to produce the maximum moment or holding power.

A fluke tripping plate or palm of sufiicient area and slope to overcome the resistance of the underwater soil or ground on the lower side of the fiukes upon initial setting.

(d) Obstruction to anchor burial to be restricted to a minimum.

(2) Adequate-size stabilizers to prevent rotation of the anchor.

ln commenting upon these design criteria, it was found, for instance, that sheer weight in itself was undesirable and unnecessary. The skillful design and proportioning of parts with adequate strength to develop the required holding power were of much more importance than sheer weight. Such achieved lightweight construction greatly facilitated the handling and emplacement of our improved heavy-duty mooring anchors.

Fluke tripping plates or palms of adequate size and proper positioning 'were found particularly necessary where the mooring anchor was being used in mud bottoms. As the anchor sank into the mud, the pressure underneath the flukes forced them upwardly and they failed to develop their required holding power. This condition was found generally in connection with the testing of shipboard type, stockless, hawse pipe stowed anchors.

The shapes, dimensions, and angular relationships of shanks and crowns in prior art anchors, where the crown is considered that portion of the anchor structure joining the flukes to the shank, are such as to preclude easy entry into the holding ground. Such crowns are comparatively massive and are usually provided with forwardly extending tips or portions making an acute angle with the shank which construction provides obstruction to good penetration into the bottom soil. Furthermore, it was found that, as the holding power of an anchor is proportional to the moment of the projected fluke area about the ocean bottom, the ratio of holding power to weight can be increased by eliminating the massive anchor crown and putting the weight saved into larger fluke areas with a proportionately longer fluke to increase the moment.

It was further determined that the fluke angle of an anchor has a definite effect upon the holding power. The fluke must bite into the bottom at an angle which will allow the fluke to penetrate rapidly to a depth which will produce the maximum moment or holding power. A small fluke angle results in rapid penetration but does not produce a large projected fluke area to resist dragging through the bottom soil. A large fluke angle presents an increased projected fluke area but does not permit proper fluke penetration. As one of the results of the extensive experimentation, it was found that the best fluke angle for sand is 35 and that for a mud bottom is 50.

It was also found that prior art anchors tended to rotate excessively when being dragged over the ocean bottom. To correct this situation, it was necessary to provide stabilizers extending laterally from the crown section. The improved stabilizers, as hereinafter described, were designed to adequately prevent rotation of the mooring anchor and increase its holding power but not to unnecessarily interfere with the penetrating ability of the fiukes.

The principal object of this invention, therefore, is to provide a comparatively lightweight, maximum performance mooring anchor constructed in satisfaction of the foregoing design criteria.

Another object of our invention is to provide a mooring anchor which has an optimum weight to holding power ratio and can be fabricated principally from steel plate.

A further object of our invention is to provide a lightweight, maximum performance mooring anchor which can be easily adapted to function in either sand or mud ocean bottoms.

Still another object of our invention is to provide a twin fluke mooring anchor having proportioned fluke areas to develop maximum holding power.

Another object of our invention is to provide a lightweight, heavy duty mooring anchor having maximum penetrability into any type of ocean bottom encountered coupled with anti-rotation means whereby the maximum holding power may be rapidly developed.

Other and further objects and advantages of our invention will be appreciated in View of the following description and drawings wherein like reference characters denote like parts throughout the several views and where- FZGURE 1 is a general plan view of our improved mooring anchor;

FIG. 2 is a side elevation thereof;

FIG. 3 is an end view thereof, partly sectioned;

FIG. 4 is an enlarged, partly sectioned, plan view taken on the line 4-4 of FIG. 3;

FIG. 5 is a sectional elevation taken on the line 55 of FIG. 1;

FIG. 6 is another sectional elevation taken on the line 66 of FIG. 1;

FIG. 7 is a sectional elevation of one of the stabilizers taken on the line 7-7 of FIG. 1;

FIG. 8 is a partial end view showing the fitting of the palm extensions shown in phantom in FIG. 2;

FIG. 9 is a cross section of the shank taken on the line 9- of FIG. 2;

PEG. 10 is a cross sectional elevation showing certain details of our invention;

FIG. v11 is a view in perspective of one of the parts;

FIG. 12 is partly sectioned elevation of our improved anchor as used in a sand bottom; and

FIG. 13 is a partly sectioned elevation of our improved anchor as used in a mud bottom.

Referring to FIG. 1, our improved mooring anchor 29 Comprises a shank 22, a pair of reinforced plate flukes 24, a crown assembly 26, a pair of stabilizers 28 and a trunnion bar 3ft.

Shank 22 may be forged, Cast, cut from plate, or fabricated from plate. its general cross sectional shape may be in the form of an elongated octagon as shown in FIG. 9. It will be noted that its greatest cross-sectional diinension is in the vertical direction, thus providing strength as well as penetrability of the shank itself into the ocean bottom. A reduced forward end portion 23 is provided with an horizontal hole for receiving the cross 'pin' 32 of the usual shackle 33. The after, or leftward, end of the shank is formed in a rectangular cross section and is provided with vertically extending abutments 34 as shown in FIGS. 2, 5, and 10. The after faces 35 of these abutments 34 are formed at an angle of 20 with the vertical transverse axis of the shank 22. As shown, these faces 35 slope upwardly and downwardly in the forward direction and, as will be more fully decribed hereinafter, serve as limiting Stops for the rotatable movement of the flukes 24 and crown assembly 26. The after end 36 of shank 22 is generally semi-circular in shape in the vertical plane and is provided with a generally concentric horizontal bore 37 of a sufficient size to accept the trunnion bar- 36. A pad eye 33 secured to the shank 22 at approximately the center of gravity of the anchor assembly, as shown in phantom in FIG. 2, may be provided, particularly in the larger sizes, for ease in handling.

The twin fiukes 24 are formed from plate steel and are provided with an off-centered ogival leading or forward 1 edge 25 and a square trailing edge 27. The leading edge 25 is scarfed or c'hamfered, as shown, for increasing the penetrability of the fluke. Triangular fluke stiffeners 29 are provided on the upper and lower surfaces of the fluke for the purpose of strengthening and stiffening the fluke. These stifieners may be made of plate steel and are secured parallel to the longitudinal axis of the fluke by welding. They are generally triangular in form with the 'after lower apex being an obtuse angle of approximately 130". This results in a backward sloping edge .31. As

shown in FIG. 6, the included angle'between the two backward sloping edges 31 of the lower and upper stiifeners is approximately 160". As willgbe seen later, this angle of 100 is important in that it not only establishes the forward entrant angle of the entire crown assembly "and the stabilizers but it assists in tripping the fluke assembly to its maximum limit of 50 with respect to the longitudinal axis of the shank.

Tripping palms 46 are rectangularpieces of plate steel that are cut the same width as the fluke. Two tripping palms are used for each fluke. They are :welded to the trailing edge 27 of the fluke and to the backward sloping edges '31 of the stilfeners 29. The included angle between the two palms is, of course, 100.

Three palm stifieners li and 42 "are provided for each fluke assembly. As will be noted from FIGS. 3 and 4, palmstiifeners 42, are made of heavier plate than palm stifieners 41. These palm stifieners 4 1 and 42 are five sided as shown, with the two larger sides 43 meeting at 'an includedfangle ofapproximately 100. At the apex of the 100 angle, a circular cut-out 44 is provided. This circular cut-out is of a diameter sufficiently large to accept the trunnion bar 39.. After being so formed, the three palm stiffeners'are welded into place. between the fmountedtripping palms with the heavier stifieners being i placed on the inboard or shank. side'of the fluke assem- V bly. Itwill be appreciated, here, that the palm stiifeners fluke assembly to swing in limited rotation with respect to the longitudinal axis of the shank.

At this point, it is to be understood that one fluke assembly comprises one fluke 24, six fluke stifieners 29, two tripping palms 40, and three palm stitfeners.

Stopper 45 is then formed from a casting, forging, or piece of plate steel. Its posterior sides 46 and general configuration match the corresponding sides, dimensions, and configurations of the palm stiffeners 42. Its semicircular cut-out 47, however, is of a greater diameter and is concentric to the generally semi-circular end 36 of shank 22. The foreward faces 48 are formed at such an angle that the extension thereof toward the center of radius of the semi-circular cut-out 47 would include an angle of approximately 120. Thus, as will be more fully described, when the fluke assembly is rotated about the trunnion bar 39, the stopper faces 48 and the 20 inclined faces of 'abutments 34 limit the rotation to 50 either side of the longitudinal axis of the shank. Furthermore, stopper is made With a sufficient thickness to slightly exceed the transverse dimension of the shank 22 at the crown end 36 plus the thickness of the two spacer washers 49 as shown best in FIG. 4.

With two fluke assemblies held in a horizontal position on each side of a similarly held shank, a trunnion bar 39 may then be inserted through the cut-outs in the fluke stiifeners and through the bore 37 in shank 22 with the spacer washers 49 on each side of the shank. Stopper 45 is then fitted between the two fluke assemblies and welded, or otherwise-suitably secured, to the'adjacent heavy palm stifieners 42. To complete the crown assembly 26, rectangular back plates 5% and 51 are welded to the fter edges of the palm stiffeners 41 and 42 as indicated in FIGS. 3 and 6. As there shown, these back plates extend the full width of the twin fluke assembly and thus, in

a conjunction with the stopper 45, solidly unite two fluke with" their :circular cut-outs embracing the trunnion bar constitute the hinge or articulated joint which. permits the and palm assemblies into one twin fluke and crown assembly. Rear pad eye 52 may be welded to the center of the outside side of plate 51 for further ease in handling the assembled mooring anchor, particularly when removing the anchor from the ocean bottom if need for such removal should occur. 7

As described thus far, the twin fluke assembly is capable of rotating to an angle of approximately 50 each side of the longitudinal axis of the shank 22. As has already been mentioned, the best fluke angle for use on or in a sandbottom has been found, by actual experiment, to be approximately 35. To limit the fluke angle, then, to 35, a pair of wedge inserts 55 has been provided'for interposition between the forward faces 48 and stopper 45 and the after inclined faces 35 of shank abutments 34. These wedge inserts are removably secured to the after end of abutments 34 by means of bolts 56 which pass through longitudinal bores 57 in aliutments 34 as best shown in FEGS. 10 and 11. The after face 58 of the wedge insert 55 is counterbored as shown to accept the heads of the bolts es, thus presenting a smooth surface. The forward face 59 of the wedge insert is inclined forwardly at an angle of 26 to match the angular face 35 of abutment 34 while theafter face 58 is inclined forwardly at an angle of 5 with the vertical transverse axis of the shank 22. Thus, as the tips of the flukes drop downwardly from their position of horizontal alignment with the longitudinal axis of the shank, the upper face 43 of stopper 45 can turn through the arc of 35 until it abuts against the after face 58 of the upper wedge insert 55. With the wedge inserts in place, the anchor is now ready for use other in a sandy bottom. As the anchor is dragged along the bottom, as illustrated in 12, the tripping palms 4t force the flukes into their maximum angle of 35 and they penetrate easily into thesand; I j V Where the anchor is to be used on a mud bottom, addi- "tional tripping palm area is required in order to counterbalance the upward pressure being exerted on the lower surfaces of the fiukes as the anchor sinks downwardly through the mud. Such upward pressure prevents the flukes from opening to the designed angle of 50 and thus prevents them from developing their maximum holding power, in order to counteract this condition, palm extensions 60, which may be seen in phantom in FIG. 2 and otherwise illustrated in FIGS. 8 and 13, are provided which may be welded to the crown assembly 26.

These palm extensions 60 comprise a rectangular plate 61 which has a width, transverse to the shank axis, equal to that of the back plates 50. Aplurality of stiffening ribs 62 are secured to one surface of the palm extension. These stifiening ribs extend below the lower edge of the palm extension plate and their lower edges 63 are formed at such an angle that as the palm extension is applied to the upper edge of the upper tripping palm 4t? and its plane coincides with the plane of the tripping palm, the lower edges 63 f the stifiening ribs 62 contact the upper or outer surface of the back plate 50. The meeting horizon tal edges or the tripping palm and palm extension are then welded together as is the lower edge 63 of the stifiening ribs 62 to the back plate 50. For additional security, the lower portion of the palm extension stiffening ribs 62 may be welded to the after surface of the tripping palm 40. Obviously, the above description pertains to the securing of the upper palm extension to the tripping palms or crown assembly. The second palm extension may be similarly installed by turning the anchor over. When the mooring anchor is to be used on or in a mud bottom, the wedge inserts are either removed or not used and the extended palms serve to trip the ilukes to their full fluke angle of 50. In order to prevent the anchor from rotating about the longitudinal axis of the shank as it is dragged along the bottom, two lateral stabilizers 28, extending from each side of the crown assembly, are provided. As shown in FIGS. 1, 3, 4, and 7, each Stabilizer is formed from four generally triangular plates welded together to form an outwardly tapering box-like structure with the larger end adjacent and welded to the crown assembly. Stabilizer main plates 64 are in the form of truncated right triangles and are welded together at an angle of 100 to match the angle formed by the tripping palms iii. Hori- 'zontal stabilizer stifieuing plate 65 is a truncated right triangle and is welded to the inner junction of tie two main plates 64. Stabilizer backing plate 66 is then formed of a truncated isosceles triangle and is welded in a vertical position to the inner surfaces of main plates 64 and to the after or outer edge of the horizontal stiffening plate 65. After the twin fluke assembly is joined to the shank by means of the trunnion bar 30, stabilizers 28 may then be welded in place on each side of the crown or twin fluke assembly with the stabilizer main plates matching with their corresponding tripping palm plates. it will be noted from FIGS. 3 and 4 that, after the stabilizers have been welded in place, stabilizer horizontal stiffening plates 65 and backing plates 66 extend horizontally and vertically across the ends of the trunnion bar 30 and serve to hold it in its proper place in the crown assembly. Gussets 67 may be welded in place between the leading edge of'the stabilizer and the outboard edge of the fluke for further strengthening the stabilizer.

Various prototype mooring anchors have been: con--' structed in accordance with the above description varying from 200 to 12,000 lbs. in weight; 42 to 186 inches in length; and 59 to 197 inches in width overall, including stabilizers. in addition to the definite angles of limited rotation of the fiukes with relation to the shank, i.e., 50 for a mud botton -aud,35-* -l for a sand bottom, it was found that a definite proportion between the fluke length and the length of the shank was necessary to develop maximum fluke moment and holding power. This proportion varied within the narrow limits of :535 and .600

in the improved mooring anchors. All such anchors, on

being proof tested, exhibited a higher holding power to weight ratio than was possessed by other prior art prototypes.

While we have described and illustrated a preferred embodiment of our invention as being constructed principa lly from steel plate materials, for ease of construction anywhere such materials may be available, it is to be understood that various parts could be of cast or forged metals and various modifications falling within the scope of the appended claims could be accomplished by those skilled in the art.

Having thus described our invention, we claim:

1. A light-weight, heavy-duty mooring anchor comprising:

a shank having an outer end with a shackle for attachment to a mooring cable, on inner end with a trunnion bar receiving bore, and integrally formed abutment means on opposite vertical edges of said shank near said bore, said abutment means having inner faces parallel to the axis of said bore and inclined outwardly toward the outer end of said shank;

a generally angular box-like crown assembly having main sides meeting in an apex pointing toward the outer end of said shank, said crown assembly being disposed equally on either side of said shank with said apex parallel to the transverse axis passing through-said shank bore and disposed toward the outer end of said shank with relation to said transverse axis;

a trunnion bar extending transversely of said shank through said bore;

means in said crown assembly for receiving the trunnion bar whereby said crown assembly is pivotally supported about the inner end of said shank;

centrally disposed massive stopper means carried by said crown assembly, said stopper means being adapted to coact with said shank abutment means to limit the rotation of said crown assembly with respect to said shank to an angle of 50 on either side of the longitudinal axis of said shank;

detachable means for attachment to the inner faces of said shank abutment means for limiting the rotation of said crown assembly to an angle of 35;

twin fiat fiukes secured to the apex of said crown assembly, said flukes being disposed on opposite sides of said shank and extending toward the outer end of said shank a distance of .535 to .600 of the length of said shank; and

a plurality of truncated triangular stifieners for each of the flat sides of said flukes, said stifieners being disposed parallel to the axis of said shank.

2. A mooring "anchor as claimed in claim 1 further characterized by the main sides of said crown assembly constituting tripping palms for said twin fiukes and wherein palm extensions are provided for attachment to said tripping palms for increasing the eitect of said tripping palms and counteracting the upward pressures exerted on said fiukes when said anchor is penetrau'ng a mud bottom and the limit of rotation of said crown assembly is predetermine lly set at 50 on either side of the longitudinal axis of sand shank.

3. A mooring anchor as claimed inclaim 1 further characterized by having angular metal plate stabilizers extending laterally from said crown assembly on each side of said shank, said stabilizers preventing rotation of said anchor about said shank, acting to assist said tripping palms in rotating said fiukes about said trunnion bar, and acting to retain said trunnion bar in said crown assembly.

8,833 Great Britain of 1896 617,3 67 Great Britain Feb. 4, 1949 Great Britain Dec. 28, 1950 I

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