AN APPARATUS FOR JUMPING A MOVING OBJECT FROM ONE PLACE TO ANOTHER AND A METHOD OF USING IT

Abstract: An apparatus (2 or 3) for jumping a moving object (10) from one place to another. Fields of application include protection of submarine installations such as pipelines (1) and cables, from damage due to dragging anchors (10) and fishing gear. The apparatus comprises a plate-like device (2 or 3) that is unstable with regard to a horizontal force over a certain strength. The deformation of the device (2 or 3) caused by such horizontal force results in a steeper direction of the resultant (14) acting on the edge (6). The frictional resistance combined with the passive soil pressure (7) thereby become able to withstand the horizontal force from the moving object (10). Subsequently the device (2 or 3) carrying the object (10) will turn around the edge (6) and thereby lift the object (10) over the installation (1). Several alternative designs of the device (2 or 3) and a method of installing it are disclosed.

Description: AN APPARATUS FOR JUMPING A MOVING OBJECT FROM ON PLACE TO ANOTHER AND A METHOD OF USING IT 1. Technical Field The invention relates to a device for lifting a moving object in a curved movement, in order, for example, to prevent daπage to another object placed underneath the device. An inportant field of application of the invention is protection of sub¬ marine installations such as pipelines and cables from damage due to drag¬ ging ships' anchors and fishing gear. 2. Background Art Several types of covers to protect submarine pipelines have been devised. U K Patent No. 1535 170, for example, discloses a cover with one hinge along its centerline. To achieve the desired pivot of the cover around one of its two supporting edges and thereby lift of the anchor over the pipeline, if a ship's anchor catches hold of the other edge, a strong reactionary horizontal force against the first-mentioned edge, however, is required. With only one hinge along the centerline of the cover such strong reaction will occur only in special cases, e g when at least -wo parallel covers are placed close against eachother. In the ordinary case the anchor chain will prevent upward movement of the central portion of the cover. 3. Disclosure of the invention It is therefore an Object of the present invention to provide a device that can lift a moving object also in cases where the local conditions do not provide for such reactionary force against pivot of the device. The principle of the present invention is to utilize the frictional re¬ sistance to a much farther extent than the known prior systems do. In the following description and in the drawings the invention will be illustrated by way of the example of a submarine pipeline to be protec¬ ted from daπage due to dragging ships' anchors. The protective system comprises an upwardly convex covering plate placed over top of the pipeline, so that the plate rests on its two longitudi¬ nally extending edges. Due to several longitudinally extending hinges in the cover, or a special ly designed unstable structure of it, the cover to a certain point is eas ly deformed by horizontal forces over a certain i-mpetus. If an anchor is dragged across the pipeline, the flukes of the anchor may catch hold of the edge of the cover. Hereby the cover will deform. The tangential point of its surface in which the anchor chain leaves the cove will rise and shift to a higher point nearer to the edge opposite the an¬ chor. The resulting force acting on this edge thereby will become steeper, so that the frictional resistance between the edge and the ground can be uti lized to withstand the horizontal drag of the anchor chain. Due to the mαrent of this drag about this edge, the cover consequently wi turn around this edge and hereby lift the anchor in a curve over the pipe line, so that damage to this is prevented. The removed section of the cover thereafter has to be repositioned. 4. Brief Description of Drawings Fig. 1 is a cross-section of a pipeline protected by a covering device in accordance with the invention, Fig. 2 is the same as Fig. 1, but the cover is here deformed by a draggin anchor, Fig. 3 is a cross-section of an alternative structure of the device accor ding to the invention, Fig. 4 is a cross-section taken along the line I-I of Fig. 5 of another alternative structure of a device covering a pipeline, Fig. 5 is a plan view on enlarged scale of the device shown in Fig. 4, Fig. β is a cross-section on enlarged scale of a special type of hinge, Fig. 7 is a cross-section on enlarged scale taken along the line II-II in Fig. 8 of an alternative type of hinge, Fig. 8 is a plan view on enlarged scale of the hinge shown in Fig. 7. 5. Best Mode of Carrying Out the Invention Consider a case where the ground consists of a non-clayey kind of soil, / e g sand, which cannot provide sufficient resistance 7 to horizontal forces, so as to allow for the desired lift of a dragging anchor 10 hooking the edge 5 of the cover 3, Figs. 1-2. By use of the present type of cover, the deformation of this will cause the direction of the resultant 14 acting on the edge 6 opposite the anchor 10 to change to such degree that the earth pressure 7 in corrbination with the friction will provide the required reaction on this edge: The direction of the force 14 exerted by the edge on the floor 0 results from the coπbination of the more or less horizontal drag force 15 of the anchor chain 15 and the vertical weights of the cover 3 and the anchor 10. If the angle S between the vertical and this resulting direction of 14 is smaller than the angle && corresponding to the coefficient of friction, k, relating to the coπbi-nation of the floor and edge materials (tang O = k) , the friction between edge and floor alone will prevent horizontal displace¬ ment of the edge 6 in relation to the floor. To maximize the angle c*C , the edges 5 and 6 therefore should be made of such material and be shaped with such uneven and possibly saw-teethed (16) lower surfaces, that the coefficient of friction, k, is maximized. To minimize the angle /3 r the invention presents the following characte¬ ristic feature of the cover 3: The structure of the cover is designed in such way that it is unstable with regard to horizontal forces over a certain strength. If the flukes 12 of an anchor 10 catches hold of the edge 5, Fig. 2, the adjacent side 17 of the cover 3 first will tend to straighten out, and the opposite side 18 of the cover will bend correspondingly and form a sharper curve than the original curvature of the cover. Fig. 2. Hereby the actual tangential point 20 in which the anchor chain 15 leaves the surface of the cover, will move higher and closer to the vertical through the edge 6 than the initial tangential point 19, Fig. 1. Consequently, the direction of the force 14 exerted on the floor by the edge 6 will become steeper. And if its angle (\ with the vertical becomes smal¬ ler than , the edge 6 will be prevented from skidding, even without any passive soil pressure 7. Thereafter the edge 5 with the hooking anchor 10 will start moving toward the pipeline. And, provided that the stiffness of the cover is properly di¬ stributed over its surface, the actual tangential point 20 continuously will move higher and closer to the vertical through the edge 6. Before the flukes 12 of the anchor 10 reaches the pipeline 1, the deforma¬ tion of the cover, however, will reach a maximum, where an inc tural stability. The point of maximum deformation is first attained at t side 18 and thereafter gradually moves toward the side 17 of the cover. When all portions of the cover have become stiffened, the whole cover wi turn around the edge 6 and thereby lift the anchor 10 over the pipeline cf. Fig. 4 in which this situation is shown with dotted lines for an alt native design of the cover. Provided that the cover 3 is made of elastic material and is continuous very long lengths, it may be able to slip back to its original position, when the anchor has fallen off the edge 5. To prevent the edge 5 from wedging into the space between anchor-shaft a -flukes, and to keep the anchor-flukes 12 away from the pipeline 1, the lower portion of either side of the cover may be bent around to be more less vertical. Alternatively, the lower portion at either edge 5 and 6 m be provided with sane other kind of expansion. Smaller anchors and fishi gear hereby will be prevented fran catching hold of the edge and will sl on top of the cover without moving it. The appropriate structure of the cover to obtain the above functioning m be obtained in various ways: As an example Figs. 1-2 show cross-sections of a cover 3 consisting of t substantially parallel plates 21 connected only by the meπbers 22. These nay be longitudinally extending parallel plates that are perpendicular t the plates 21. As there are no diagonals in the cross-section, such as i ordinary bearing structures, this structure is unstable with regard to horizontal forces. To begin with the two plates 21 can be mutually displ ced in their own planes, without much resistance from the members 22. A cover with such structure caught by an anchor therefore, initially will bend on its side opposite the anchor, until the deformation of the cover las reached the point where the deformation itself prevents the two sheet 21 frcm mutual displacement. From this moment on the two sheets together with the connecting eπbers 22 will be interlocked and form a stable stru ture able to withstand the static moment due to the weight of the anchor and the cover itself. Depending on the elasticity of the materials involved, the two sheets 21 may be kept at a distance all the way down to the lower edges 5 and 6, or they may meet and be joined together along these edges, Figs. 1-2. Appropriately the distance between the two sheets 21 varies from a πaximu at the centerline to a minimum at the edges of the cover, cf. Figs. 1-2. Maximum strength of the cover hereby is obtained at the centerline where ^ the maxiπtum bending moment will occur during the anchor's ride on the cover over the pipeline. Furthermore, the minimum strength and stability of the structure of the cover occurs at the edge portions where the bending mo- m≥nt will be iriinimum, and where maximum bending of the cover will be needed. The cover shown in Figs. 1-2 may be made of for example aluminium, glass- fibre-reinforced polyester, other sort of plastic, or steel that may be coated with for example titanium. Another example of structure of the cover is shown in Fig. 3 which is a cross-section perpendicular to the pipeline, where the two sheets 21 in stead of the eirbers 22 are interconnected by elements 23 which to a certain point can rotate in relation to eachother. The rotation may be limited by an expansion 24 of each element 23. The elements 23 for instance may be made of concrete. In this design one. of the sheets 21 may be replaced by strings of appro¬ priate material, e g aromatic polyamide. The sheets 21 may be made of steel, aluminium, titanium or other metal, or glassfibre-reinforced polyester, plastic or other suitable material. A third alternative design of the cover is shewn in Figs. 4-7. The device consists of long parallel elements 2 joined together by hinges 4. To save material, the elements 2 in their longitudinal direction may contain channels 30. In their longitudinal direction the elements 2 may be interconnected by staggering their ends and fit one set of projecting ends in between the projecting ends of the adjacent set of elements, Fig. 4. The hinged connection between two neighbouring elements 2 may be formed in several ways. The type of hinge shown in Fig. 6 is appropriate in case the elements 2 are fabricated by an extrusive type of fabrication. Figs. 7-8 show a more traditional hinge with a pin 33 through the stag¬ gered expansions of the two elements 2. In both types of hinges their pivoting movement is limited in either direction by pans 31 and 32, respectively. When the cover 2 is placed over the pipeline 1, and the weight of the cover tends to straighten out the convex cover, the upper pans 31 of neighbouring eleπents 2 will be pressed close together. If a dragging anchor hooks one edge of the cover and turns the cover around the other edge, the lσwer pans 32 will limit the bend of the cover. A preferred material for fabrication of the elements 2 is concrete which may be reinforced. To reduce the lifting forces of the currents and waves, and/or to further sedimentation under the cover 2 or 3, if this is desired, at least porti¬ ons of the cover may be perforated, especially along its top. In many cases no sedimentation -underneath the cover is desirable, since a open space between pipeline and cover allows for convenient regular in¬ spection of the pipeline by means of an unmanned TV-camera pulled by stri along "" the pipeline from either end of the pipeline. 6. Industrial Applicability The invention may be used in cases where a dragged object is to be lifted over an other object, over a cleft, etc. The length of the lifting device in direction perpendicular to the direction of movement of the dragged object nay be suited to the local circumstances. When used for protection of a submarine pipeline, cable or the like, the protective cover may be fabricated on land, assembled to very long length supplied with buoyancy means, and towed to the installation site at a ' ≤ui table level off the bottom. The distance between cover and bottom during the tow may be controlled by heavy chains hanging from the cover and drag ging on the bottom. O ? v-

Claims: CLAIMS : 1. An apparatus for juπping a moving object from one place to another, comprising a plate-li-ke device that in the direction of movement of said object is upwardly convex and unstable with regard to a horizontal force over a certain strength, said plate-like device by such impetus becoming deformed, and the distance between the two edges of said plate-like device thereby becoming decreased until a certain point, at which point said plate-like device becomes stable and strong enough to carry the weight of said moving object in a pivotal movement around the edge of said plate¬ like device. 2. An apparatus according to Claim 1, wherein either edge portion of said plate-like device is steeper than rest of said device. 3. An apparatus according to Claim 1 or 2, wherein said plate-like device is provided with apertures. 4. An apparatus according to Claim 1, 2 or 3, wherein said plate-like device consists of two substantially parallel thin plates that are inter¬ connected by meπfoers perpendicular to said two thin plates. 5. An apparatus according to 1, 2 or 3, wherein said plate-like device consists of two substantially parallel thin sheets that are interconnec¬ ted by parallel tube-like meπtoers that are placed close together and to a certain degree can rotate in relation to eachother, the rotation being limited by expansions on the surfaces of said tube-like merrbers. 6. An apparatus according to Claim- 5, wherein at least one of said two substantially parallel thin sheets is replaced by strings of appropriate material. 7. An apparatus according to Claim 4, 5 or 6, wherein the distance be¬ tween said two substantially parallel thin plates, sheets or strings de¬ creases from the middle toward either edge of said plate-like device. 8. An apparatus according to Claim 1, 2 or 3, wherein said plate-like device consists of parallel elements that are hinged together by hinges which allow for mutual rotation of said elements between two points limited by expanded parts of said hinges. 9. An apparatus according to Claim 8, wherein said elements contain parallel channels. 10. An apparatus according to any preceding claim, wherein said plate- like device is made of elastic material and fabricated and/or asseπbled to such long lengths that said plate-like device will slip back to its original position, if said moving object turns it around. 11. An apparatus according to Claim 8 or 9, wherein said plate-like device is made of concrete. 12. A method of laying over a submarine installation to be protected, a row of plate-like devices according to Claim 1, wherein said plate-like devices are fabricated, asseπbled to form a long, continuous length and supplied with buoyancy and ballancing means on land and thereafter tσwed off the bottom to the installation site, where they are lowered to the floor.

Inventors: LARSEN O
Applicants: LARSEN O
Application year: 1981
Main classification: F16L1
IPC codes: E02B3, F16L1, F16L57, H02G1, H02G9