US3850128A

US3850128A - Vibratory anchor

Info

Publication number: US3850128A
Application number: US00379707A
Authority: US
Inventors: J Lovell
Original assignee: Ocean Science & Eng
Current assignee: Ocean Science & Eng; OCEAN SCIENCE AND ENG INC US
Priority date: 1973-07-16
Filing date: 1973-07-16
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26

Abstract

An anchor assembly for embedment into a formation beneath a body of water, comprising an anchor section having an elongated hollow shaft and radially extending tapered plates attached to the lower end thereof, a vibratory drive unit and a releasable coupling for connecting said drive unit to said shaft. The vibratory forces fluidize the sea floor whereby the anchor tends to sink by its own weight. After embedment, the coupling is deactivated to permit retrieval of the drive unit.

Description

United States Patent [191 Lovell [45] Nov. 26, 1974 VIBRATORY ANCHOR [75] Inventor: Jack Lovell, McLean, Va.

[73] Assignee: Ocean Science and Engineering,

Inc., Rockville, Md.

221 Filed: July 16,1973

21 Appl. No.: 379,707

[52] US. Cl 114/206 R [51] Int. Cl B63b 21/26 [58] Field of Search 114/206 R, 206 A, 207, 114/208 R; 52/153-155; 175/5,10, 19, 55, 56; 279/38 [56] References Cited UNITED STATES PATENTS 895,438 8/1908 Delany 279/38 2,490,378 12/1949 2,643,629 6/1953 3,194,326 7/1965 3,279,133 10/1966 3,431,880 3/1969 3,490,550 1/1970 3,604,519 9/1971 Chelminski 114/206 R 3,621,805 11/1971 Smith 114/208 R R25,764 4/1965 Robinson 114/206 A FOREIGN PATENTS OR APPLICATIONS 218,428 12/1941 Switzerland 279/38 Primary ExaminerTrygve M. Blix Assistant Examiner--Galen L. Barefoot Attorney, Agent, or Firm.lohn J. Byrne; Edward E. Dyson 5 7 ABSTRACT An anchor assembly for embedment into a formation beneath a body of water, comprising an anchor section having an elongated hollow shaft and radially extending tapered plates attached to the lower end thereof, a vibratory drive unit and a releasable coupling for connecting said drive unit to said shaft. The vibratory forces fluidize the sea floor whereby the anchor tends to sink by its own weight. After embedment, the coupling is deactivated to permit retrieval of the drive unit.

4 Claims, 9 Drawing Figures PATENTEL rwvzw 3.850.128

SHE! u 0! 4 lii PRIOR ART Huh PRIOR ART This invention relates to improvements in anchors for mooring floating bodies such as drilling platforms or the like, and more particularly to improvements in anchors which are power driven into the sea floor.

The anchor of this invention includes, in combination with a power unit, an anchor section which penetrates the sea floor comprising an elongated hollow shaft having radially outwardly extending tapered plates equispaced around the periphery of a shaft at its bottom end. The power unit is a vibratory driving head which is mounted at the top of the elongated shaft and which is releasably connected thereto through remotely controlled, power-operated connecting means. The anchor section is driven into the sea floor to a depth substantially equal to the length of the elongated hollow shaft. The vibratory power unit or driving head incorporates counter-rotating eccentric masses which generate and transmit axial forces down the elongated shaft to the penetration point. The vibratory forces cause the anchor section to be in a constant state of rotational movement under vertical forces. When the desired depth is reached, the power unit is remotely released from the anchor shaft and is retrieved for subsequent use.

As mentioned above, the power unit generates vibratory forces which are produced through counterrotating, unbalanced masses arranged and synchronized by gears so that the centrifugal forces of the rotating masses are in phase and additive in the vertical direction, and canceling in the horizontal direction. The masses are driven by hydraulic or electric motors. The principal of embedding by vibration requires that sufficient motion be imparted to the soil surrounding the anchor section to produce a state of fluidization, whereby the anchor tends to sink of its own weight as in a viscous fluid.

The vibratory anchor of this invention has several advantages over conventional anchors. Unlike conventional anchors, which can be pulled only in the direction in which they are to be set, the vibratory anchor of this invention can take an equal amount of pull in all directions. In addition, on a per weight basis, the anchor of this invention can take twice the pull of the best lightweight, conventional anchor in the horizontal direction to be set. While a conventional anchor must be dragged to be set and thus cannot be accurately set in terms of location, the power-driven, vibratory anchor of this invention is driven straight down into the sea floor and therefore. can be set at a precise location. The capacity of the anchor of this invention to sustain high vertical loads after being precisely positioned enables it to moor objects with a taut moor with as little as merely 'a one-to-one ratio of anchor line to water depth.

The anchor assembly of this invention can be used for specialized moorings in consolidated sediments in water depths up to l0,000 ft. It is useful for a wide range of special mooring applications such as for oceanorgraphic data buoy stations, surface and subsurface instrument buoys, ships, submarines beneath the surface and manned or unmanned sea platforms. Quite often, these objects are anchored with dead weights or with conventional anchors which are ill suited to the unusual demands put upon them.

It is an objective of this invention to provide a power driven anchor assembly which is lightweight in construction and simplistic in design.

It is a further objective of this invention to provide a power-driven anchor capable of penetrating a relative hard surface formation of the type for which conventional drag anchors or the like have been found to be.

unsuitable.

It is aother objective of this'invention to provide a power-driven anchor assembly incorporating a vibratory driving head which fluidizes the subsurface formation such that the anchor is embedded therein under its own weight.

it is another objective of this invention to provide an anchor having a vibratory driving unit capable of selectively generating vibratory forces over a wide range of frequencies.

It is another objective of this invention to provide an anchor which after embedment is capable of substaining loads in any direction of pull.

It is another objective of this invention to provide an anchor having a vibratory driving head capable of generating peak driving forces of 30,000 lbs. for driving the anchor into the sea floor up to depths up to ft. in water depths of 10,000 ft.

The anchor assembly of this invention includes an anchor or ground-penetrating section, a vibratory powerdrive unit attached to the anchor and connecting means for releasably attaching the power unit to the anchor. Additionally, the system is designed to be controlled from a mother ship and can be accurately positioned in any desired location to anchor a floating body such as the aforementioned oceanographic data buoy stations, surface and subsurface instrument buoys, ships, submarines beneath the surface and manned or unmanned sea platforms. Though the vibratory drive unit can be powered by electric motors, preferably a hydraulic power system is used including a hydraulic power supply pump positioned on the mother ship, hydraulic motors for powering the vibratory unit, hydraulic conduits extending between the motors and the hydraulic pump and a suitable control system for selecting a particular frequency over a range in accordance with the type of surface in which the anchor is embedded.

' A particular vibratory motor unit which may be utilized with the anchor assembly of this invention is described in US. Pat. No. 3,490,550 to E. E. Horton dated Jan. 20, 1970, entitled VIBRATORY CORlNG APPARATUS. Basically, in a preferred embodiment the power to the vibratory drive unit is provided by a hydraulic pump driven by a six-cylinder horsepower industrial gasoline engine. The vibratory drive unit is mounted on top of the anchor shaft during the embedment operation and delivers up to 30,000 lbs. of sinusoidal force at frequencies up to 60 cycles per second. Upon embedment to the desired depth, the releasable connecting means is actuated from aboard ship to release the driving unit from the embedded anchor. The unit is retrievable by means of a cable or the like extending between the ship and the unit. The vibratory drive unit incorporates counter-rotating, eccentric masses which generate dna transmit axial forces down the shaft to the anchor. These impulses cause the an-* .chor to be in a constant state of motion under vertical force. This motion fluidizes the bottom material'around the anchor permitting the anchor to embed itself.

The anchor in a preferred embodiment comprises an elongated, hollow tubular shaft having a plurality of tapered, radially outwardly extending plates equi-spaced about the periphery of the shaft at one end thereof. The drive unit is connected to the other end. A tether bar is pivotally connected to the shaft. An anchoring chain is connected to and extends between the tether bar and the object to be moored. The hollow shaft is open at the bottom to facilitate penetration in stubborn subsurface formations. The tether bar is pivotally attached to the collar which is slidably received on the anchor shaft and a fixed collar is provided on the shaft above the tether collar and below the upper end of the shaft. A compression spring is seated between the immovable collar and. the fixed collar and functions as a shock absorber once the anchor has been embedded and is in operation. The vibratory motor is mounted on the top of the hollow shaft and is connected thereto via releasable connecting means. The connecting means are retrievable with the drive unit and comprise an annular, cylindrical housing extending downwardly from the drive unit and slidably receiving an annular split sleeve or collet therein. The annular cylindrical housing closely engages the outer surfaces of the split sleeve to maintain the sleeve in a closed cylindrical configuration when the sleeve is within the confines of the annular or cylindrical housing. A double-acting jack is attached to the power unit and has a piston rod extending from the lower end thereof. The collet is attached to the end of the rod. The cylinder is double-acting and upon actuation thereof through a suitable hydraulic fluid source, for example a hand pump or the like, the split sleeve will be caused to slide within the annular or cylindrical housing. A locking lug extends axially upwardly from the hollow shaft of the anchor section and is firmly attached to the shaft. The lug is adapted to be received within the split sleeve such that when the sleeve is within the annular housing, it will tightly engage the lugand hold the power unit and anchor section in assembled relationship. After the anchor has been embedded, the hydraulic cylinderis actuated to push the split sleeve out of the cylindrical or annular housing whereupon the segments separate and release the lug to disconnect the power unit from the anchor section. The entire anchor assembly is initially lowered into the water by means of acable or the like attached to the upper end of the power unit. and after the anchor is embedded, the same cable is utilized to retrieve the power unit and the releasable connecting means.

The hollow shaft of the anchor of this inventionis formed preferably of steel pipe material of any suitable diameter. A 4 in. diameter pipe has been found to be satisfactory. The length of the pipe shank is variable, being a function of the soil conditions and the'holding power required.

The tether bar has a bale at one end for attaching the anchor cabin or cable. The other end of the bar is pivotally connected to a slidable and rotatable collar on the anchor shaft, whereby the tether bar can swing around the shaft and slide axially relative thereto.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein.

FIG. 2 is a cross sectional view taken along the lines 2-2 of FIG. 1;

FIG. 3 is a cross sectional view taken along lines 33 of FIG. 1;

FIG. 4 is a cross sectional view of the connecting means of the anchor assembly of this invention showing the anchor section and the power unit in the connected or attached position;

FIG. 5 is across sectional view of the connecting means of this invention showing the connecting means in its releasing position;

FIG. 6 is an elevational view of the anchor assembly of this invention after embedment and just after release of the power unit and connecting means;

FIG. 7 is an elevational view of a prior art form of a fluke arrangementused with a vibratory power unit;

FIG. 8 is a view similar to that of FIG. 7 but showing the disposition of the pivotal fluke assembly after a pulling force has been applied to the tether bar; and

FIG. 9 is a cross section view taken along lines 99 of FIG. 7.

The anchor assembly of this invention can best be described with initial reference to FIG. 1 wherein the numeral 10 generally indicates the entire anchor assembly, which is comprised of three sections; namely, the power unit 16, the connection means 14, and the anchor section 12.

The anchor section 12 comprises an elongated hollow tubular shaft 15 of circular cross section having an open bottom end 17 to facilitate penetration of the anchor in particularly stubborn subsurface formations. A plurality of tapered radially outwardly extending plates 18 are attached to and equi-spaced about the periphery of the shaft 15 adjacent the open end 17. The plates taper from top to bottom toward the open end and are provided with beveled edges 20 to facilitate ground penetration. The plates and shaft are formed of steel with the shaft body consisting of steel pipe. The length of the shaft is variable, being a function of the soil conditions and the holding power required. The plates 18 are welded or otherwise fixedly attached to the shaft 15 and FIG. 2 shows the equi-distance' spacing of the plates 18 about the shaft. In the embodiment shown, four plates are used; however, it is to be understood that fewer or more plates may be employed depending upon the particular requirements at the time of use.

Forming part of the anchor section 12 is a tether bar assembly 22 comprising an elongated tether bar 24 having an aperture 26 at its free end 28 thereof for attachment of an anchor chain 30 which extends from the tether bar to the object to be moored. The other end of thetether bar is pivotably connecte at 32 to a radially extending apertured lug 34 which is fixedly attached to a collar 36 which is rotatably and slidably mounted on the shaft 15. A fixed collar 38 is firmly attached to the shaft 15.and is vertically spaced from the slidable collar 36. The fixed collar 38 and'the slidable FIG. I is a view in elevation of the anchor assembly 1 of this invention;

collar 36 serve as top and bottom stops or seats for coil spring 42. The spring functions as a shock absorber against pull-out forces which are applied to the tether The power drive unit 16 will not be discussed in detail in this application, however, it is to be understood that it is substantially similar to the hydraulic vibratory motor described in assignees US. Pat. No. 3,490,550 to E. E. Horton, dated Jan. 20, I970, entitled VIBRA- TORY CORING APPARATUS. Basically, the drive unit comprises a pair of

hydraulic motors

44 and 46 which are powered by a hydraulic pump positioned on the mother ship. Hydraulic fluid is supplied to each

motor

44 and 46 by a pair of hydraulic conduits generally indicated by the

numerals

48 and 50. The pump on the surface ship is driven by any suitable prime mover such as an industrial gasoline engine, and the output thereof to the motors is controlled by any suitable control means.

The drive unit 16 embeds the anchor section 12 by generating vibratory forces which cause the anchor to be in a constant state of rotational motion under vertical force. The bottom material around the anchor is fluidized, permitting the anchor to embed itself. The vibratory forces are generated by counter rotating eccentric masses which generate and transmit axial forces down the shaft 15 to the anchor. The counter rotating unbalanced masses are synchronized by gears so that the centrifugal forces of the rotating masses are in phase and additive in the vertical direction and offsetting in the horizontal direction. In lieu of the

motors

44 and 46, the eccentric masses may be driven by other means such as electric motors. The masses are not shown but it is to be understood that they are within housing 52 and the operation thereof can be readily understood with reference to the abovementioned US Pat. No. 3,490,550. I

An eyelet 54 is fixedly attached to the upper surface of the housing 52 to which a supporting cable 56 is attached. The cable leads to a winch on the surface ship and is used to initially lower the entire anchor assembly to the point where the anchor is to be embedded and to recover the power unit 16 and connecting means 14 once the anchor section has been embedded. A tether bar retainer 58 extends outwardly from the housing 52 to prevent the tether bar from swiveling during the embedment operation. Though the retainer is not clearly shown in the drawings, it is to be understood that it comprises a plate having a forked outer end to define a centrally extending open-ended slot which receives the upper end portion of the tether bar 22.

FIG. 3 is a cross sectional view looking downwardly on the movable collar 36 to which the tether bar 24 is attached. The collar 36' has a pair oflugs 34 attached thereto and extending radially outwardly. Each of the lugs has an aperture 32 therein and a space therebetween for receiving one end of the tether bar 24. An aperture 33 in the tether bar is aligned with the apertures 32 and a pivot pin 35 is inserted therethrough and held in place by suitable lock rings 37.

The connection means 14 of this invention is best illustrated in FIGS. 4 and 5 and includes a hydraulic, double-acting jack 70 which is attached to the housing 52 of the power unit 16 by means of a pivotal connection generally indicated by the numeral 72. The jack 70 includes a cylinder and piston which divides the cylinder into upper and lower chambers. Inlet-outlet

hydraulic conduits

76 and 78 communicate with the upper and lower chambers respectively. The jack is encased in a cylindrical housing 74 which is attached to the underside of the housing 52 of the power unit 16. Apertures 80 and 82 receive inlet,

outlet fittings

84 and 86 to which the inlet-

outlet conduits

76 and 78 are connected respectively. The cylinder 70 may be actuated by a simple hand-operated pump. A four-way valve is employed for selectively pressurizing either the upper or the lower chamber depending upon whether the piston rod 90 is to be extended or retracted.

A second cylindrical housing 88 extends downwardly from the housing 74 and is of a diameter less than that of the housing 74. A piston rod90 extends from the jack and into the housing 88. The outer end of the piston rod is threaded at 92 and is received in the upper portion of a split cylindrical collet or sleeve 94. The collet 94 is comprised of two cylindrical halves which are held together in a cylindrical configuration by the close confines of the inner surface of the sleeve 88. The internal surface of the collet is likewise threaded to tightly grip the threaded portion 92 of the piston rod 90 when the collet is within the sleeve'88. Likewise a lug or projection 96 having an upper threaded end portion 98 is fixedly secured to the upper portion 40 of the shaft 15 by means of a block 100 which is received within a hollow shaft 14 and which is secured in position by pins 102 which extend through the sidewall of the shaft. The collet grips the threaded portion 98 of the lug 96 when the collet is within the confines of the cylindrical sleeve 88.

In the view shown in FIG. 4, the connecting means is in the locked position wherein the power unit is firmly attached to the anchor section. The lower edge portion of the sleeve 88 is telescopically received within the shaft 15 to a depth limited by the stop ring 104. The double-acting jack 70 causes the split collet 94 to move within the sleeve 88 such that when it is actuated to extend the rod 90 to the position shown in FIG. 5, the collet is outside of the sleeve 88 and will separate into cylindrical halves to release the threaded end portion 98 of the lub 96. Therefore, the anchor section 12 will be released from the power section 16. When initially assembling the anchor prior to lowering it into the water, the piston rod is extended to the position shown in FIG. 5 wherein the collet is firmly pressed around the portion 98. The piston rod is retracted to draw the collet and the lug up past tapered edge portion 108 surrounding the opening of the sleeve 88 and into the sleeve wherein the collet is-held in a closed position tightly gripping both the piston rod 90 and the lug 96. The piston rod is retracted to the point wherein the upper edge of the shaft 15 is tightly held against the stop 104. The assembly maintains this position during the entire embedment procedure.

FIG. 6 is substantially identical to that of F1601 except for showing the anchor section 12 embedded below the surface 8 of a subsurface formation. In the view showin in FIG. 6, the power unit and connecting means has just released its hold on the anchor section and is being withdrawn to the mother ship. As mentioned earlier, the anchor is embedded by means of the vibratory forces generated by the power unit such that the matter in the subsurface formation surrounding the anchor is fluidized. When the formation is in this condition, the anchor will readily move to its desired depth, preferably the length of the shaft 15.

A particular fluke arrangement which is known to the prior art and which has been used successfully by the assignee herein is shown in FIGS. 7 through 9. The arrangement of FIGS. 7-9 is disclosed for background purposes only and no claim of invention is made thereto. The arrangement of these figures is substantially identical to that of FIGS. l6 with the exception of the construction of the fluke in the anchor section. Therefore, only that portion will be described. The

configuration of the fluke is generally indicated by the numeral 200 and can best be understood with reference to the cross sectional view of FIG. 9. The fluke comprises a back plate generally indicated by the numeral 202 which consists of steel plate cut into a generally circular configuration and then bent at 204 along a vertically extending diameter to provide two side sections 206 and 208 which form an angle of approximately 120. This plate is attached to socket 205 which receives the end of shaft 15. Front plate 210 is of the configuration of a quarter segment of a circle and is welded to the socket and extends radially outwardly therefrom. The resulting cross sectional configuration of the rear and front plates is a Y shaped configuration. The edges of the plates are beveled so as to facilitate penetration.

Small baffle plates

212 and 214 are welded to sections 206 and 208 respectively of the back plate 202 and extend parallel to the plate 210. Horizontally and angularly extending

struts

216 and 218 reinforce the

plates

212 and 214 and further provide increased resistance to pull out. These struts stiffen the fluke and increase pullout resistance by preventing the soil from sliding along the faces of the

plates

206, 208 and 210. The struts meet at the forward edge of the plate 210 and are connected thereto by means of a pin 220 which extends through apertures in the struts and in the plate 210.

The fluke is normally held in the position shown in FIG. 7 by means of a cable 222 shown in dotted line configuration which extends axially through the hollow shaft and exits at the top thereof into a threaded portion 224. In the embodiments of FIGS. 1 through 6, this threaded portion was fixedly secured to the shaft near the top thereof. However, in the embodiment of FIGS. 7-9 the portion 224 is attached to the cable which passes through suitable cable guides or spools 225 fixed to the interior of the shaft 15 and is connected to the fluke at its inner portion. When the connecting means releases its hold on the threaded portion 224, the tension on the cable is relaxed and the fluke is free to pivot downwardly, as shown in FIG. 8, when a load is placed on the tether bar by the object being moored. The fluke pivots downwardly as shown by means of a double linkage arrangement generally indicated by the numeral 226 which includes a pair of

links

228 and 230. The link 228 is pivoted at one end to the fluke by means of pin 220 and at the other end of the 7 link 230. The other end of the link 230 is pivotally attached to a lug 232 which is fixedly secured to a nonmovable collar 234 which is attached to the shaft 15. It is to be understood that the fluke assumes the position shown in FIG. 8 when upward force is exerted on the tether bar and that it readily resists forces from any direction.

In a general manner, while there has been disclosed effective and efficient embodiments of the invention, it should be well understood that the invention is not limited to such embodiments as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

' I claim:

1. An anchor assembly for penetrating formations beneath a body of water comprising a vibratory drive unit, an anchor section, connecting means releasably connecting said drive unit to said anchor section, said anchorsection comprising an elongated hollow tubular shaft having a top end and a bottom end, a plurality of equi-spaced plates tapered from top to bottom attached to said shaft adjacent the bottom end and extending radially outwardly from said shaft, beveled edges on said plates, said bottom end of said shaft being open and having tapered edges and extending below said plates, said connecting means connecting the top end of said shaft to said drive means; said connecting means comprising an annular housing connected to said drive unit, an annular split sleeve slidably received in said housing, a lug on the top end of said shaft and received in said split sleeve, said housing causing said sleeve to tightly grip said lug, and means for selectively shifting said sleeve out of said housing to release said lug, tether means and means attaching said tether means to said shaft.

ments of said collar.

Claims

1. An anchor assembly for penetrating formations beneath a body of water comprising a vibratory drive unit, an anchor section, connecting means releasably connecting said drive unit to said anchor section, said anchor section comprising an elongated hollow tubular shaft having a top end and a bottom end, a plurality of equi-spaced plates tapered from top to bottom attached to said shaft adjacent the bottom end and extending radially outwardly from said shaft, beveled edges on said plates, said bottom end of said shaft being open and having tapered edges and extending below said plates, said connecting means connecting the top end of said shaft to said drive means; said connecting means comprising an annular housing connected to said drive unit, an annular split sleeve slidably received in said housing, a lug on the top end of said shaft and received in said split sleeve, said housing causing said sleeve to tightly grip said lug, and means for selectively shifting said sleeve out of said housing to release said lug, tether means and means attaching said tether means to said shaft.

2. The anchor of claim 1 wherein said means for shifting said sleeve is a hydraulic piston and cylinder assembly having a piston rod attached at one end to said piston and at the other end to said split sleeve.

3. The anchor assembly of claim 1 wherein said means for attaching said tether means to said shaft comprises a collar slidably and rotatably connected on said shaft, and means pivotably connecting said tether to said collar.

4. The anchor assembly of claim 3 and including spring means on said shaft for buffering sliding movements of said collar.