US2075827A - Anchor - Google Patents

Description

April 1937- J K. NORYTHROP ET AL 2,075,327

ANCHOR Filed Nov. 20, 1955 2 Sheets-Sheet 2 IN VEN TORS- .JOHN- K. NORTHROP. HARRY M. GESNER.

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A TTORNE Y Patented Apr. .6, 1937 PATENT OFFICE ANCHOR John K. Northrop, Los Angeles, and Harry M.

Gesner, Inglewood, Calif.

Application November 20, 1933, Serial No. 698,776

- 6 Claims.

Our invention relates to anchors such as may be used for mooring or holding all types of movable objects, particularly water craft, and more particularly to anchors of the shank and fluke type designed to develop holding power largely independent of the weight of the anchor.

Among the objects of our invention are: to provide an anchor having an unusually large ratio of holding-power to Weight; to provide an anchor which will penetrate the bottom by the angular positioning of a planar fluke; to provide an anchor having structural dimensions and angular relationships as will enable the anchor to bury itself in penetrable bottom; to provide an anchor of exceptionally light weight which may be used, for example, in places where weight is at a premium; to provide a simple and eiilcient airplane anchor; to provide an anchor which may be folded in compact form for easy stowage; and to provide an anchor operating by virtue of planing characteristics rather than by weight.

Other objects of our invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but we do not limit ourselves to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

In the (drawings which illustrate several preferred embodiments of our invention:

Figure l is a top view of a single fluke anchor.

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

Figure 3 is a cross sectional view through a fluke, taken as indicated by the line 3--3 in Figure 2.

Figure 4 is a view in elevation, showing the junction of a fluke arm shank and stock as viewed from the rear.

Figure 5 is a sectional view, taken as indicated by the line 55 in Figure 4.

Figure 6 is a side elevational view of a double fluke anchor.

Figure '7 is a cross sectional view of the fluke arm, taken as indicated by the line 7-1 in Figure 6.

Figure 8 is a sectional view, taken as indicated by the line 8-43 in Figure 6.

Figure 9 is a view, partly in section and partly in elevation, taken as indicated by the line. 9-9 of Figure 6.

Figure 10 is a cross sectional view of the shank, taken as indicated by the line lfl-Illin Figure 6.

Practically all existing anchors depend, to a large extent, on their weight for the holding power developed. Various types and shapes of fluke have been evolved in the past to furrow' the bottom and resist dragging of the anchor by the moored craft. In general, it may be stated that the fluke sizes and shapes and their relation to the shank and line of pull in existing anchors, are such that comparatively great anchor weight is a vital necessity to the proper engagement of the fluke in the bottom, and that the fluke alone would be relatively ineifective to develop any considerable holding power if the anchor weight was substantially decreased.

This fact often has been proved in comparative tests of cast anchors of similar shape but having varying specific gravity. Attempts have been made to obtain satisfactory holding powers in anchors cast of aluminum alloys instead of bronze or iron. These tests have always shown that the holding power of the aluminum anchors is greatly inferior to the heavier types, and that weight is essential in order to obtain proper fluke engagement and holding power. The statement may be further substantiated by the fact that fluke angles which are now in almost universal" use, are such that the forces .under load tend to disengage the fluke from the bottom, and these forces must be counteracted by the weight of the anchor on the fluke to maintain proper engagement. The anchor of our invention employs new principles to develop its holding power.

In broad terms, the anchor of our invention has a fluke shape, fluke-shank angles, and interrelation of other parts, such that when a dragging load is applied to the shank the fluke enters the bottom and buries itself, this action being due almost solely to the pull on the shank from the anchor cable, and only in a very minor degree to the weight of the anchor.

Such an anchor may be designed on a basis of fluke size and structural strength from strong alloysteels, taking into account strength alone without regard to weight. The resulting structure will develop a much higher ratio of holding power to weight than conventional types, and at the same time is less affected by bottom conditions, as the force tending to cause entrance of the fluke into the bottom is existant regardless of the type of bottom. On the other hand, conventional typ s depending on weight are afiected by bottom consistency, which to a large degree regulates the penetration and holding power of the fluke.

That the above theory is sound may readily be determined by comparative tests of various anchors. American and British naval aircraft organizations have conducted a large number of nassuro JUN 4 1941 tests on various types of anchors for use on sea planes and flying boats where the saving of weight is particularly important. In general, these tests have shown a holding power-weight ratio 5 for the anchors tested of from 5 to '1 to to 1, depending upon the type of anchor and bottom conditions, whereas the anchor of our invention has developed ratios up to and including 200 to 1.

Referring now to the drawings, Figures 1 and 2 show two elevational views of a typical anchor of our invention, having one fluke only. Basically, the anchor comprises a shank I, a fluke arm 2, a fluke 3, and a cross arm or stock 4. These essential parts may take various forms, but certain relationships which are essential should be maintained in orderto achieve the best results.

In Figures 2 and 6 the various lengths and angles are illustrated and may be defined as folows:

1. Shank length. The axial distance along the shank from the point of rope attachment to a line projected at right angles to the shank axis and touching the rear edge of the fluke at the center line thereof.

2. Fluke arm length. The shortest distance from the axis of the shank to the rear edge of the fluke at the center line thereof.

3. Fluke length. The length of the center line of the fluke.

4. Fluke angle. The angle between a line parallel with the shank axis passing through the rear edge of the fluke at the center line thereof and the center line of the fluke.

As an example, for a ratio of fluke arm length to shank length of 1 to 3 and a ratio of fluke length to shank length of 1 to 2%, a fluke angle of 21 is satisfactory. If the fluke angle is increased to 26 the shank length should be increased 30%, and if the fluke angle is the shank should be increased in length 60% for best results. In general it may be stated that 25 is approximately the best fluke angle for an anchor of reasonable proportions, and that the maximum fluke angle for best results with an unusually long shank is around 35,

In this connection it is interesting to note that in a series of many examples of the ordinary type of fluke and shank anchors depending on weight for their holding power, tested by various agencies, the fluke angle varied from 35 to 70, with the large majority near the high limit, further establishing the fact that the tested anchors were principally dependent on weight for the engagement of. fluke and bottom.

Fluke arm length and fluke size can be varied throughrather wide limits. Ratios of fluke arm length to shank length of from 1 to 6 to 1 to 3 give good results. Some advantages attend the use of the longer fluke arms, however, as such proportions allow the fluke to bury itself more deeply and develop greater holding power. The deeply buried fluke also produces a pitching moment which buries the cable end of the shank and helps it to resist high angles of cable pull.

We prefer to form the anchor of our invention, for the efficient functioning of the device, of high strength alloys such as stainless steel for example. These alloys are used not only to save weight but also to allow the various parts to be made as 70 thin as possible. The natural tendency of the fluke to bury itself is greatly aided by making the fluke 3 and fluke arm 2 smooth, thin, and with sharp edges. Initial penetration may be further aided by providing the fluke with a central sharp 5 point 3 so that in hard bottom penetration will start immediately. Due to the fact that the total weight of the anchor is small, the acute angle of this sharp point is of great help in preventing dragging immediately after bottom is contacted, and once penetration starts the anchor at once planes to its final position. The sharpness of the point, therefore, together with the thin fluke section adjacent thereto gives practically immediate penetration. The fluke arm is preferably of open section as resistance to bottom penetration at this point causes a sharp limitation in the depth to which the fluke will bury itself with a corresponding decrease in holding power.

Advantages may be gained by the use of a stock or cross arm, having a substantial area normal to the shank. We prefer, therefore, to make the stock 4 of triangular section having a flat surface substantially normal to the shank. Such an arm is pulled into a soft bottom by the downward force of the fluke, and increases resistance to the forward motion of the anchor. The cross arm or stock 4 not only holds the fluke at such an angle as to engage the bottom and cause the point to enter, but is preferably made hollow and welded so as to be water-tight. When the anchor is thrown overboard the buoyant force exerted by the hollow stock causes the anchor to fall, at reasonable depths, fluke down, so that the point will readily engage the bottom.

Referring again to the drawings for a more detailed description, the shank l is of U-shaped section and so formed that the opening of the U faces the fluke 3. We prefer to taper the shank so that it is slightly deeper at the junction of stock and fluke arm than at the attachment end. A cable may be attached to the free end of the shank by a shackle 5.

The anchor shown in Figures 1 to 5 is adapted to fold. The fluke 3 is welded or otherwise fastened to lips 6 formed on parallel fluke arm ribs 1. It is desirable to provide the fluke with a longitudinal stiffening bend 9 between the attachment points of the ribs l. The free ends of the ribs I are preferably bent over toward each other and butt-welded, and a strengthening plate I!) welded across the butt-weld. The fluke arm ribs 1 adjacent the strengthening plate in, and the shank i adjacent the large end, are provided with triangular apertures through which the triangular stock 4 may pass, thus locking the shank l to the I fluke arm 2 in proper angular relation. The stock 4 has a centrally located depression H, and the shank carries a spring I2 which has a projection l3 on its free end adapted to fall into the depression II when the stock is centrally located with respect to the shank and fluke arm. A reenforcing strip I4 is fastened to the shank I around the triangular apertures to strengthen the shank at this point.

Given the anchor as shown in Figures 1 and 2, the procedure necessary to fold the anchor is as follows. The spring I2 is depressed, thereby allowing the stock to be completely withdrawn through the apertures in the fluke arm and shank. We prefer to fit this cross arm into the hollow portion of the shank for carriage. The fluke arm is then loose and slidable upon the shank and may be folded until the fluke lies flat with the shank. Center punches l5 are provided on both ends of the shank to prevent the fluke arm from sliding off and becoming separated from the shank. The anchor, thus dismantled, may be packed in an extremely small space.

Figures 6 to 10 show a double fluke anchor.

'In this case we prefer to make the stock I of two U beams l6, welded back to back. In this case,'

as in the single fluke anchor, the fluke arms 2 are formed of two fluke arm ribs 1, but they are not joined at their free ends. The shank is pro- 5 vided with a pair of pivot bolts l'l, passing through an aperture in a corner of the ribs 1, and through the shank, to form a pivot for each arm. Ahead of and at right angles to the pivot bolts l'l, fastened to the outside of 'the shank are cross arm brackets I8 carrying cross arm pivot bolts I! which pass through, on each side, a pair of locking plates 20 to which cross arm sections 2| are welded or otherwise fastened. We prefer to form these cross arm sections of reversed 6- l5 shape, the flat surface being normal to the shank with the open portion of the channel to the rear. On the end of each fluke arm rib opposite the pivot, is an oblong opening 22 which registers with a similar opening 23 in the shank when the 20 fluke arm is in operating position. The end of each locking plate 20 is provided with a tongue 23 which is adapted to pass through the openings 22 and 23 when the cross arm sections stand at right angles to the shank. In order that the 25 locking plates may remain in position, the tongue is provided with an offset 24, and the plates on each arm are slightly sprung toward each other so that when the tongues are in the apertures the offset catches under the shank wall and holds the 30 locking plates in position.

Having the anchor of Figure 6 in erected position, the anchor may be dismounted by forcing each cross arm inward so that the locking plates are spread and the offset released. The cross 35 arm sections may then be folded down flat against the shank, the tongues being withdrawn from the apertures in the fluke arm ribs and the I shank. This leaves the fluke arms free to pivot on the pivot bolts I1, and the fiukes may then be 40 folded in line with the sections and the shank.

Figures 7 and 9 show the attachment of the fluke to the fluke arm ribs, the attachment being practically the same as in the single fluke anchor of Figures 1 and 2. As in the double fluke type 5 the mere presence of a cross arm or stock insures that one or the other of the fiukes will engage the bottom; it is not necessary, in this case, that the stock have any buoyancy.

In operation, the anchor is thrown overboard 50 and irrespective of whether the anchor is of the single or double fluke type, the point of the fluke will be in a position to engage the bottom and cause the point to enter. As the cable load is applied, the anchor gradually turns about its 55 shank axis and develops its maximum power with the fluke buried almost straight down and with the stock engaging or buried in the bottom material. I a

It is obvious that the condition then existing is 60 stable and that dragging of the anchor will not cause it to turn and disengageas is the case with many stockless types. a

In the anchor shown in Figures 1 and 2, the stock not only provides flotation but also provides 65 a certain resistance to the anchors passage through the water, and thus aids the anchor to fall, point down, when cast off in water of reasonable depth. This particular type of anchor is eminently suitable for temporary or emergency use, and has the advantage of compactness and light weight. 5

The location of the stock adjacent the fluke arms rather than at the opposite end of the shank, as is often the case, insures the burying of the stock in the bottom even at large angles of pull, and so further contributes to the holding 10 power.

It is obvious that there are other means of locking and folding the various component parts of the anchor, and we do not wish to be limited to the particular construction shown, other constructions within the scope of the claims being apparent to those skilled in the art.

We claim:

1. An anchor comprising a fluke attached to a shank by a fluke arm, said anchor having a ratio of fluke length to shank length of approximately 1 to 2 a ratio of fluke arm length to shank length of 1 to 3, and a fixed fluke angle of approximately 21, whereby the holding power in penetrable bottom is substantially independent of 25 weight.

2. An anchor comprising a fluke attached to a shank by a single fluke arm, said anchor having a ratio of fluke length to shank length of approximately 1 to 2 a ratio of fluke arm length to shank length of 1 to 3, a fixed fluke angle of approximately 21, whereby the holding power in penetrable bottom is substantially independent of weight, and a stock extending through the junction of said arm and shank, at right angles thereto, said stock having a buoyant factor associated therewith suificient to cause said anchor to fall through water fluke down.

3. An anchor comprising a single fluke at-M tached to a shank by a fluke arm, and a stock passing through the junction of said arm and shank, said stock being hollow and water-tight and of sufficient buoyancy to cause the point of said fluke to contact bottom when dropped through water. a

4. An anchor comprising a fluke attached to a shank by a fluke arm, and a stock passing through the junction of said arm and shank, said stock being shaped to provide a relatively high resistance to forward motion andrelatively low resistance to downward motion when said stock is engaging the bottom with the fluke of said anchor buried therein.

5. An anchor comprising a fluke attached to a shank by a fluke arm, and a stock passing through the junction of said arm and shank, said stock being of triangular section and positioned to have a flat surface normal to the shank.

6. In an anchor having a fluke attached to a shank by a fluke arm, a stock passing through the junction of said arm and shank, said stock being hollow and water-tight, of triangular section and positioned to have a fiat surface normal to the shank.

. JOHN K. NORTI-IROP.

HARRY M. GESNER.

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