US2861534A - Sea anchor - Google Patents

Description

Nov. 25, 1958 L F FEHLNER 2,861,534

SEA ANCHOR lled Oct. 4, 1955 2 Sheets-Sheet 1 5. v ,if l 2% INVENTOR Leailfzef; a

ATT(`)RNEYS NOV. 25, 1958 F FEHLNER 2,861,534

SEA ANCHOR Filed Oct'. 4. 1955 2 Sheets-Shea?l 2 INVENTOR ATTORNEYS SEA ANCHOR Leo F. Fehlner, Bethesda, Md., assignor to the United States of America as represented by the Secretary of the Navy Application ctoher 4, 1955, Serial No. 538,542

4 Claims. (Cl. 114-209) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or tor the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention is directed to a novel sea anchor; and more particularly to a sea anchor which is very stable in operation and which has a high drag coetlicient.

Heretofore when the need arose to keep a ship with its bow to the waves various emergency measures were resorted to, e. g., the use of items such as buoyant oil drums, various shaped Weights, and rigged sails. Metal truncated cones were also employed and were towed with the large end toward the stern of the ship. As with the emergency devices, the truncated cone had a very low drag coetiicient, its resistance or drag was erratic and it also suffered from instability because of poor hydrodynamic design since it depended for buoyancy on the speed of tow.

The sea anchor of the present invention obviates the disadvantages inherent in prior sea anchors and provides a stable high resistance sea anchor of practical size which produces in a tow cable a steady tension which varies with the speed of tow. The sea anchor comprises a solid or tubular frame in the shape of a polygonal pyramid covered with a high resistance or drag metal` mesh; said frame being adapted to be towed from an attachment at the apex of said pyramid such that the etective center of resistance of the anchor is moved to a point behind the attachment. The angle of the pyramid is not critical and the coeicient of drag -of the anchor is directly proportional to its area and the resistance ot the anchor varies with the square of the velocity of the movement of the anchor relative to the water. As the coetlicient of drag varies with the area, anchors of larger size which necessitate more rigid frames are constructed of metal tubing such that the anchor will be made slightly negatively buoyant and thereby be maintained at an optimum depth. Weighting one side of the polygonal base keeps the anchor from rotating about its tow line.

An object of the invention is the provision of a novel sea anchor.

Another object of the invention is to provide a stable sea anchor having a high drag coeicient.

Still another object is to provide a stable high resistance device which acts to produce a specified tension in a tow cable when towed in water at a specified speed.

A further object is to provide a high resistance device which acts in conjunction with a towed object to stabilize said object.

A still further object is to provide a high resistance expendable device whereby the drag of a minesweeping gear may be simulated.

Other'objects and many of the attendant advantages of this invention will be readily appreciated Vas the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

i 2,861,534 Patented Nov. 25, 1958 Fig. 1 shows an embodiment of the sea Yanchor drawn to a scale of 1:1 utilizing a tubular frame;

Fig. 2 shows a side elevation of the sea anchor of Fig. 1;

Fig. 3 shows a side elevation of the lattice on one panel;

Fig. 4 shows a modification of the frame drawn substantially to a scale of 5/16=l' having a larger drag characterisitc than that of Fig. 1;

Fig. 5 shows a further modification of a frame drawn substantially to a scale of 5A6=1 having a still larger drag characteristic than that of Fig. 4;

Fig. 6 shows a bottom structure utilizable with that shown in Fig. 5; and, i

Fig. 7 shows the central support for the device of Fig. 5.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Figs. 1 and 2 a sea anchor 10 having a Vpyrarnidal hollow watertight Welded frame with a hexagonal base, said frame comprising hollow tubular base sides 11, a hollow central hexagonal support 12 vertically displaced from said base sides, and a plurality of hollow radially extending ribs 14. One of the hollow sides 11 is weighted with sand 13 or the like, confined to that one hollow side. The ribs 14 are secured as by a weld to the vertices 15 of the sides 11 comprising said base and to the central support 12 thereby forming a plurality of sloping triangular bays 16. While many types of perforated covering may be used, i. e. lattices, screens, etc., each bay of the pyramidal frame is entirely covered by an expanded metal 17. It will be noted that the expanded metal comprises a plurality of individual undulating strands 18, 19, 20, 21, 22, N. The undulations of alternate strands being in phase and the undulations of adjacent strands being out of phase. The expanded metal 17 on each bay is aligned true and identical with and secured to the expanded metal on adjacent bays, as by a weld at 23 in Fig. l, to insure a straight tow. Secured to attachment 12 is an eye 24 or thelike whereby a tow line may be fastened to the anchor.

Referring to Fig. 3, it will be seen that the expanded metal forms a plurality of steps 25 which are at an angle a to the horizontal plane which is substantially equal to the slope 0 of the pyramid. This positioning of the expanded metal 17 offers a high resistance to flow of water therethrough and is responsible for the high drag coeiicient of the anchor. Neither the slope 0 of the pyramid nor the angle a is critical; however an angle of approximately 10, for each, has been found satisfactory. The anchor of Fig. l was tested at 10 knots and produced a drag of 6,100 pounds.

As the drag coefficient is directly proportional to area for a given speed of tow, Figs. 4 and 5 show larger more rigid frame structures designed for anchors having greater coeicients of drag than that of Fig. 1. Fig. 4

shows a frame identical to that of Fig. l except for size, having a further polygonal rib support structure comprising ribs 26 welded to the radially extending ribs 14 at the middle portions thereof, for obtaining a drag coeiiicient greater than that of the anchor of Fig. 1. In

device thatis.y inexpensive to construct and is expendable.

Obviously ,many modiicationsfand variations of the present inventiontarepossible in the lightof. the above teachings. Any construction can be used that isv compatible with .the :hydrodynamic characteristics of the device and does not alter its basic shape. It is therefore tobe understoodlthatwithinthescope of the appended c ,laimstthe,inventionmayrbe practiced otherwise than as specifically described.

Whatisfclaimed is:

l. `Asca. anchor comprisingaramehaving a polygonal base perimeter, radially extending ribs having their respective outerends secured to.- said base` at the vertices of the sides forming said polygonal perimeter, hub means centrally `disposed ,of saidperimeter, said ribs havingtheir respective inner ends secured to said hub means and forming withsaidbase perimeter a pyramidalframe, a tow line receiving meansraixed to saidrhub means and extending away from said. polygonal `base perimeter, and an expanded metalmember having a high resistance to drag ycovering said vframe, said .expended ,metal being adapted toA resist the ow of water'through saidframe.

v2. A sea anchor as ldefined in claim 1 Whereinsaid ribs andbase perimeter are tubular and Whereirrone `side ofsaidbase perimeter is weighed.

3.7A sea` anchor comprising a pyramidal frame, a lattice covering on said frame comprising aplurality of rigid undulatingmemhersghe planesin vwhich said respective undulating members lie being substantially parallel, the face of said members being disposed at an acute angle tothebase planeof said frame to form a series of steps extending between the youter periphery of the base of said frame and the apex, said steps extending at substantially right angles to the longitudinal axis of the anchor, and a tow line receiving means secured to said apex at the side thereof remote from the base of said pyramidal frame adapted to connect a tow line tothe anchor.

4. A device for maintaining a predetermined tension in a tow cable comprising a pyramidal frame having a polygonal base, a series of rigid undulating strands covering said frame, adjacent undulations connected to said frame in opposed phase relation and each strand connected at its maximum amplitude point to a minimum amplitude point on an adjacent undulation thereby forming a lattice, and means at the apex of said pyramid for attaching a tow cable, said lattice extending away from the-base of said pyramidal frame toward said apex, whereby said pyramidal frame is adapted to be towed with its apex forwardmost.

References Cited in-the le of this patent UNITED STATES PATENTS 289,224 Clarke Nov. 27, 1883 2,358,233 Jorgensen Sept. 12, 1944 FOREIGN PATENTS 5,826 France Aug. 17, 1840 258,958 Great Britain Oct. 4, 1926 594,287 @Great Britain Nov. 7, 1947 791,827 France Oct. 7, 1935

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