IL289407B2 - Protective cable nets system (pcns) - Google Patents

Description

PROTECTIVE CABLE NETS SYSTEM (PCNS) FIELD OF THE INVENTION: [Para 1] The present invention relates to the field of defense systems.

More particularly, the present invention relates to a system for blocking ballistic and direct hit munitions and drones.

BACKGROUND OF THE INVENTION AND PRIOR ART: [Para 2] Munitions such as antitank missiles, rockets, shells, bomblets, and other artillery or explosive objects are used and often fired by army units or terrorist organizations into urban areas, critical facilities and military zones. Drones, with or without explosives that can shoot and drop bombs and may penetrate the aerial perimeter of the mentioned areas and zones. There is a great need for protection of several specific zones from these fired objects and drones. Another example of such zones are zones that have special installations, infrastructures, arsenal, and populated areas.

[Para 3] US 2010/0102166 relates to an apparatus and method of missile interception. The missile interceptor comprises a net body with a plurality of sections and at least one missile trajectory effector, preferably an exploding ring. A missile, passing through the net body, picks up the ring, which explodes once the missile passes a sufficient distance away from the missile interceptor.

[Para 4] WO 2008/114261 relates to a barrier, wherein the barrier is an upwardly immobilized barrier (UIB) comprising a barrier, comprising at least one netting adapted to avoid or hinder penetration of actuated members, and at least one balloon immobilizing the netting from the nettings top portion.

[Para 5] US 2010/0294124 relates to a device and a method for protecting objects against rocket propelled grenades having a hollow nose cone including a netting of knotted and coated super strong fibers disposed in front of the object, in such a manner that the nose cone of a rocket caught in the netting will penetrate one of the meshes of the netting and be deformed through strangulation, thereby disabling the detonator.

[Para 6] Analysis of Geometrically nonlinear Structures, Second Edition, Chapter 7 - CABLE NETS AND FABRIC STRUCTURES; by Robert Levy and William R. Spillers; 2003 Kluwer Academic Publishers; pages 151-186, relates to cable nets and fabric structures formed by tailoring portions thereof.

This publication gives the background of the calculations and design of the hereunder described invention.

[Para 7] The design of three-dimensional doubly curved spatial cable nets and fabric structures can be described in terms of three events: shape finding, analysis, and patterning. Simpler cases of three-dimensional singly curved or plane structures are a rather trivial matter. In the process of shape finding, the designer specifies a set of parameters and then computes other parameters finally resolving the details of the shape of the structure. Under analysis, loads are applied to a structure whose shape is known and the response to these loads computed. Patterning is concerned with how a curved surface is to be formed from rolls of fine cable nets, fabric or soft membranes, solid membrane plates and cables.

[Para 8] The process of shape finding can be thought of roughly in terms of stretching a cable net, fabric, or a membrane over a frame of arbitrary shape. (For example, in the skylight problem of Figure 8A, the geometry is fixed along both crossed arches and the base.) Clearly the cable net, fabric or membrane must follow the frame at the boundaries and certain tensions can be specified on these boundaries. But just as clearly, the locations of the cable net, fabric or membrane points within the frame must be determined from the equations of equilibrium and in some cases the material parameters. Finding the locations of these internal points is the process of shape finding.

[Para 9] In the early days (Frei,1973) and in the absence of the computer, physical models were commonly used in the design of fabric structures and cable nets. It is now conventional wisdom that small-scale models are not sufficiently accurate either for the prediction of forces or the patterning of the cable nets or the fabric.

[Para 10] If needed to find a shape which is in equilibrium, this can be done by applying loads to, for example, a stretched elastic sheet and then using the deformed sheet or a scaled version of it as the shape. There is nothing wrong with doing so but care is required since loads applied to a sheet may introduce stress concentrations which may not be desired in the structure under design. The basic reference to this method is Argyris, et al. (1964).

[Para 11] Any computer program for nonlinear structural analysis can be used to achieve shape in this manner but it does not appear common to do so. Pertinent to this is the fact that the cable nets, fabrics, or membranes now commonly used in permanent structures cannot tolerate large strains without tearing.

[Para 12] It has been noted by Schek (1974) that if the ratio of the bar force to its length is held constant in a cable net, the associated geometry can be found by solving a system of linear equations. (A similar statement can be made for a finite element fabric or membrane model.) This approach is frequently used in the design of fabric, membrane or cable net structures.

[Para 13] The force density method is based on the fact that the force on the end of a truss bar can be represented by the product of the bar force and a unit vector in the direction of the bar as shown in Figure 8AB. Here i n is the unit vector of member i, iF is the bar force of member i, and iL is the length of member i. The components of the force vector can be written as ( ) ( ) ( ) ( ) ( ) ( )C A C A C A Z ZLF Y YLF X XLF izi iyi ixi - = - = - = i i i F F

Claims (4)

- 42 - CLAIMS: 1. A combined net structure comprising: a non-planar coarse net with a grid-like structure comprising a plurality of coarse cables wherein longitudinal coarse cables intersect with latitudinal coarse cables to form a plurality of coarse cells; cutouts of a "fine net" attached to said coarse net, wherein said "fine net" comprises a plurality of adjacent fine cables (forming a fine cable net); a fabric; a membrane (soft or solid); solid tiles; stuffed hollow tiles; fluid filled hollow tiles; wherein each non-edge fine cable is attached to two adjacent fine cables on each of its sides at a plurality of locations along their lengths forming attachment points, wherein said fine cable net is arranged in a form of an array of fine quadrangular cells with said attachment points constituting the vertices of said fine quadrangular cells. 2. The combined net structure according to claim 1, wherein each "fine net" cutout is substantially coextensive in shape with one or more coarse cells. 3. The combined net structure according to claim 2, wherein all the coarse cells are attached to "fine net" cutouts. 4. The combined net structure according to claim 2, wherein the "fine net" cutouts are connected to the coarse net such that portions of a fine cable - 43 - net or edges of the fabric, the membrane (soft or solid) or the solid tiles of said "fine net" cutouts are attached to corresponding portions of a coarse cable of the coarse net by means of connecting elements that hold said "fine net" and said coarse cable together. 5. The combined net structure according to claim 1, wherein the coarse net further comprises connecting elements that connect the intersecting longitudinal coarse cables with the latitudinal coarse cables at the intersecting points. 6. The combined net structure according to claim 1, wherein the fine quadrangular cells are square or rhombic cells. 7. The combined net structure according to claim 1, wherein the distances between two adjacent attachment points of two adjacent non-edge fine cables are substantially the same; and wherein the imaginary line which bisects and is perpendicular to the imaginary line connecting two adjacent attachment points of two adjacent non-edge fine cables passes through an attachment point of one of said two adjacent non-edge fine cables with its other adjacent fine cable. 8. The combined net structure according to claim 1, further comprising one or more edge cables attached to the perimeter of the coarse net. - 44 - 9. The combined net structure according to claim 8, wherein the diameter of the edge cables is between 15mm and 50mm. 10. The combined net structure according to claim 1, wherein the diameter of the coarse cables is between 8mm and 40mm. 11. The combined net structure according to claim 1, wherein the diameter of the fine cables is between 3mm and 6mm. 12. The combined net structure according to claim 6, wherein the square or rhombic cell diagonals are between 20mm and 60mm. 13. The combined net structure according to claim 1, wherein the longitudinal coarse cables and the latitudinal coarse cables have predetermined lengths and are attached to each other at pre-calculated locations marked along their lengths. 14. The combined net structure according to claim 13, wherein the predetermined lengths are such that the coarse net formed comprises a 3- dimensional structure. 15. The combined net structure according to claim 6, wherein an imaginary line connecting two adjacent attachment points of two adjacent non-edge - 45 - fine cables is parallel to the longitudinal coarse cables or to the latitudinal coarse cables. 16. A system comprising: at least one column; the combined net structure according to claim 1; plurality of anchors; wherein the combined net is attached to said column and to said plurality of anchors. 17. The system according to claim 16, wherein the combined net structure is quadrangular and one of its vertices is attached to the column, and wherein said system comprises three anchors and three vertices of said combined net structure are each attached to one of said anchors. 18. The system according to claim 16, wherein the column is height adjustable. 19. The system according to claim 16, wherein the anchors are concrete blocks. 20. The system according to claim 16, wherein the system comprises one or more additional combined net structures according to claim 1; wherein the one or more additional combined net structures are attached to the column and to the plurality of anchors. 21. The system according to claim 20, wherein the one or more additional combined net structures are quadrangular; - 46 - wherein one of the one or more additional combined net structure vertices is attached to the column and the other one or more additional combined net structure vertices are attached to the anchors. 22. The system according to claim 16, comprising two columns and two anchors; wherein the combined net structure is quadrangular comprising a first vertex, a second vertex, a third vertex and a fourth vertex; wherein said first vertex is attached to a first column and said second vertex is opposite to said first vertex and is attached to a second column, and wherein said third vertex and fourth vertex are each attached to one of said two anchors. 23. The system according to claim 22, further comprising one or more additional quadrangular combined net structures, two columns and two anchors; wherein each of said one or more additional combined net structures is quadrangular and comprises a first vertex, a second vertex, a third vertex and a fourth vertex; wherein the one or more additional quadrangular combined net structures first vertex is attached to the column; and wherein the one or more additional quadrangular combined net structures second vertex is opposite to said first vertex and is attached to a second column; and - 47 - wherein said third vertex and fourth vertex of said one or more additional quadrangular combined net structures are each attached to one of said two anchors. 24. A system comprising:

1. two intersecting arc structures;

2. two parallel arc structures;

3. one arc structure;

4. any combination of arches and columns a combined net structure according to claims 1; wherein the combined net structure is spread over said two intersecting arc structures, two parallel arc structures, one arc structure, any combination of arches and columns.