Truss Array for Supporting Devices Within a Fluid Medium

1. Field of the Invention

The invention relates generally to a support apparatus and, in particular, to apparatus for horizontally supporting devices within a fluid medium.

2. Description of the Prior Art

It is known that a plurality of surface floats may be used to horizontally support devices within a fluid medium such as water. However, such an array of surface floats is visible from above the water, and is subject to surface currents or other forces within the water which affect the horizontal positioning of the devices.

It is an object of this invention to provide an apparatus which horizontally supports a plurality of devices within a fluid medium.

It is a further object of this invention to provide an automatically deploying apparatus for horizontally supporting devices within a fluid medium.

The invention relates to an apparatus for horizontally supporting one or more devices within a fluid medium of known density. A primary supporting truss comprises the following elements: first means for supporting a first mass at a given position within the fluid medium; a second mass having a density less than the known density of the fluid medium connected to said first mass by second means; and a third mass having a density greater than the known density of the fluid medium connected to the first mass and the second mass by third means. A fourth means for supporting the devices connected to the first mass and means for deploying said apparatus are associated with the primary truss. The means for deploying may be fifth means for engaging currents within the medium and connected to the fourth means. At least one secondary supporting truss may be connected between the primary supporting truss and the fifth means.

For a better understanding of the present invention, together with other and further objects, reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.

FIG. 1 is an illustration of a preferred embodiment of the invention as deployed within a heavier-than-air fluid medium;

FIG. 2 is a vector diagram of the forces involved in an embodiment of the invention including a primary supporting truss and first and second secondary supporting trusses;

FIG. 3 is an illustration of an alternative embodiment of the invention; and

FIGS. 4A-4D are illustrations of alternative embodiments particularly illustrating the means for supporting the anchor at a given position within the fluid medium.

The preferred embodiment of the truss array of the invention as illustrated in FIG. 1 includes a primary supporting truss P, secondary supporting truss S1, secondary supporting truss S2, and secondary supporting truss S3. However, the invention may include any number of secondary supporting trusses.

The primary truss P includes anchor 1 and means for supporting the anchor 1 at a given horizontally stable position within fluid medium 2 of known density. FIG. 1 illustrates a heavier-than-air medium, such as water, wherein anchor 1 is a mass of density greater than the known density of the medium and the means for supporting the anchor at the given position comprises surface float 3 such as a transmitting buoy having a density less than the known density of medium 2 and line 4 interconnecting surface float 3 and anchor 1. A compliant means, such as resilient element 4a, may be provided between line float 3 and anchor 1 to isolate the surface movement of float 3 from the subsurface structure of the array. Furthermore, the apparatus according to the invention may include any means for supporting the anchor 1 at a given position within the fluid medium including, but not limited to, the embodiments illustrated in FIGS. 4A-4D and discussed below.

Primary truss P further includes subsurface float 5a having a density less than the known density of the medium and connected to anchor 1 via line 6a. Weight 7a having a density greater than the known density of the medium is connected to subsurface float 5a via line 8a and to anchor 1 via line 9a. Devices 10 to be horizontally supported within the medium 2 may be connected to or suspended from line 9a, anchor 1 or weight 7a. Drogue 11 may be connected to weight 7a for deploying the apparatus and maintaining the apparatus in a relatively stable position so that devices 10 supported by line 9 are in an approximately horizontal plane. FIG. 1 illustrates drogue 11 connected to weight 7a via subarrays S1, S2 and S3. However, the invention may comprise the single primary array P with drogue 11 directly connected to weight 7a. In addition, means may be employed with primary array P for determining the direction of orientation of the array. For example, a geophone or flux-gate compass may be supported by anchor 1 or float 3.

Each line interconnecting the floats, weights, anchor and drogue is preferably a flexible cable. However, any means may be used for interconnection including, but not limited to, rods, ropes, chains, telescoping members or resilient members or any combination thereof.

Each secondary supporting truss, such as secondary trusses S1, S2, and S3 illustrated in FIG. 1, includes a subsurface float 5b, 5c, 5d having a density less than the known density of the fluid medium 2. Each secondary truss also includes a weight 7b, 7c, 7d having a density greater than the known density of the fluid medium 2.

In the embodiment as illustrated in FIG. 1, each subsurface float 5b, 5c, 5d of each secondary truss S1, S2, S3 is connected to the weight 7a, 7b, 7c, respectively, of the last adjacent truss. In particular, secondary truss S1 is connected to primary truss P so that subsurface float 5b of the secondary truss S1 is connected to weight 7a of the last adjacent truss (primary truss P) via line 6b.

Each weight 7b, 7c, 7d of each of the secondary trusses S1, S2, S3 is connected to the weight 7a, 7b, 7c, respectively, of the adjacent truss and to the subsurface float 5b, 5c, 5d which is part of the same secondary truss. Specifically, weight 7b of the secondary truss S1 is connected via line 8b to subsurface float 5b and via line 9b to weight 7a of adjacent primary truss P.

Additional devices 10 may be connected to line 9b and/or weights 7b, 7c, 7d in horizontal line with line 9a. Secondary trusses S2 and S3 are similarly connected, as illustrated. Drogue 11 is connected to the last weight of the last truss of the array which, as illustrated in FIG. 1, is weight 7d.

In operation, the entire apparatus is released in the medium as a package, preferably with all interconnecting lines coiled. Upon release, surface float 3 begins to float and anchor 1 is forced downward by gravity causing line 4 to uncoil into an extended position which defines the depth D of the anchor 1 and, subsequently, the devices 10. Naturally occurring currents in medium 2 deploy drogue 11, which forces lines 9a, 9b, 9c, 9d to uncoil. Buoyant forces within the medium move subsurface floats 5a, 5b, 5c, 5d upward completing deployment of the entire array and providing a stable horizontal support for devices 10.

FIG. 2 illustrates the forces involved in an apparatus of the type illustrated in FIG. 1 including a primary truss and two secondary trusses. In particular, force F represents the tension between surface float 3 and anchor 1. Force W.sub.o represents the weight of anchor 1. Forces U.sub.1, U.sub.2 and U.sub.3 represent the upward forces created by subsurface floats 5a, 5b and 5c, respectively. Forces W.sub.1, W.sub.2 and W.sub.3 represent the gravitational forces on weights 7a, 7b and 7c, respectively. Force D represents the force created by drogue 11. T.sub.1 -T.sub.9 represent the tension in the lines.

Assume that the system is at equilibrium, that the devices 10 have the same density as the medium, and that D is known since the force resulting from naturally occurring shear currents acting on a drogue can be measured or calculated. Choose line lengths 6 and 8 to be equal to form each truss as an isosceles triangle with angles a and b. For convenience, assume

Summing the vertical forces, acting on node g, yields

Summing the horizontal forces acting on node g yields

or T.sub.g =D-0.5T.sub.6

Combining

In order to create tension in line 9, 0.58W.sub.3 must be selected to be slightly less than D or W.sub.3 must be slightly less than 1.72D. However, if the devices 10 are supported only by the weights, line 9 need not be tensioned. In addition, if D is much greater than 0.58W.sub.3, D will cause the entire apparatus to move. Since D can be measured or calculated, W.sub.3 may be selected to meet these condition and is known.

T.sub.5 and T.sub.6 are equal since summing the horizontal forces acting on node f yields

Or

Therefore, U.sub.3 can be determined by summing the vertical forces acting on node f

Or

Since the system is at equilibrium and line 9 is a straight line, T.sub.9 =T.sub.8 =T.sub.7. T.sub.4 and T.sub.5 are equal since summing the horizontal forces acting on node e yields

W.sub.2 can now be determined by summing the vertical forces acting on node e.

Or

By similar analysis, it can be shown that

and that

Further similar analysis yields that W.sub.o should equal 2W.sub.3. However, W.sub.o may be chosen much greater than 2W.sub.3 to quickly deploy the apparatus and enhance its stability at the desired depth D.

The angle .theta. between F and W.sub.o can now be found. Summing the vertical forces at node a yields

Or ##EQU1##

Summing the horizontal forces yields

Or ##EQU2##

The two unknowns, F and .theta., can now be calculated from the two equations (1) and (2) derived from the analysis at node a. Once F is determined, the minimum buoyancy of surface float 3 can be determined. As a result, all forces on all nodes and all angles are known and can be calculated when the apparatus is at equilibrium.

FIG. 3 illustrates an alternative embodiment of the invention wherein like reference numerals refer to the same structure as illustrated in FIG. 1. In the alternative embodiment of FIG. 3, the drogue 11 is connected to the last subsurface float 5d of the last secondary supporting truss S3'. In addition, each secondary supporting truss S1', S2', S3' is connected to its adjacent truss by connection to the subsurface float 5a, 5b, 5c of the adjacent truss P, S1', S2', respectively, rather than by connection to the weight of the adjacent truss as illustrated in FIG. 1. For example, secondary supporting truss S1' is connected to subsurface float 5a of primary supporting truss P'. The result is that lines 6a, 6b, 6c, 6d form the horizontal line to which devices 10 may be connected.

The invention has been described with particular regard to its structure for supporting devices 10 in a horizontally stable position by attachment of the devices to line 9 and/or weights 7a, 7b, 7c, 7d of FIG. 1 or line 6 and/or floats 5a, 5b, 5c, 5d of FIG. 3. However, it is contemplated that the devices may be supported in any position which is horizontally stable by varying the support distance between line 9 or line 6 and the devices. For example, devices 10 may be suspended from an arched cable connected to anchor 1 and drogue 11 or may be located at various horizontal positions by suspending the devices from line 6 or line 9 by cables of various length.

It is contemplated that this apparatus may be used in any fluid medium to support any kind of device. For example, devices such as transducers, antenna elements, lights or any type of sensing or transmitting device may be supported. FIGS. 4A-4D illustrate various means for supporting a primary truss within the fluid medium 2. FIG. 4A illustrates subsurface float 12 connected by line 13 to anchor 14. Anchor 14 may rest on floor 15 or may be suspended from subsurface float 12 by connecting surface float 16 to subsurface float 12 by line 17. Alternatively, float 12 may be eliminated by interconnecting lines 13 and 17. Weight 7 and subsurface float 5 are interconnected between float 12 and drogue 11 for deploying the apparatus. FIG. 4B is an alternative embodiment of FIG. 4A wherein the drogue 11 is connected to float 5 rather than weight 7. FIGS. 4C and 4D illustrate primary trusses wherein the anchor and means for supporting the anchor at a given horizontally stable position comprises a rigid member 18 affixed to base 19.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.