Envelope For Underwater Cable, Drag Ropes Or The Like

Abstract

Cable and drag rope jackets are constructed from snapped together strips having streamline profile, and joints only at the leading and trailing edges of the profile. Each strip has recesses which mutually cover each other upon assembly to receive one or more cables or a rope.

Description

BACKGROUND OF THE INVENTION

The present invention relates to improvements for underwater cable, drag ropes, anchor ropes and the like.

It is known presently that an elongated element with circular cross-section offers resistance to fluid flow (transverse to its extension) which depends primarily on the diameter of the element, the square of the fluid velocity, and a coefficient of resistance which depends on the contour of the cross-section of the element. The diameter of, for example, a drag rope is chosen primarily on basis of the load the rope has to take up and pull. Thus, the diameter is not available as parameter for selecting or modifying the flow resistance of the rope. Fluid flow velocity is, of courses, an external condition to be met and not a selectible parameter. The only parameter left for control is the coefficient of resistance.

Different kinds of cable jackets have been suggested for reducing the said coefficient, at least theoretically down to 1/15 of the coefficient value for unjacketed cable. Further reduction in the resistance results automatically from the fact that a smaller resistance means smaller load, so that the load bearing characteristics (namely the cross-section) can be reduced further.

These mutually beneficial conditions, however, are offset by the fact that the cable jacket is normally made part of the cable itself and becomes an integral component thereof. Thus, the contour of the cable presents a storage problem when reeled in. Moreover, when parts of the cable become defective, the entire cable has to be replaced, or at least a section thereof requiring cumbersome cable splicing techniques.

Some cable jackets are known which are constructed in (longitudinal) sections, and the sections are interconnected through appropriate fittings. However, the joints of the sections are invariably regions of increased flow resistance. Such increase becomes noticeable for long ropes or cables. Also, objects may lodge in the joints, increasing the flow resistance further and adding to the load. The problem is compounded by the fact that the known constructions for sectioning cables provide joints at hydrodynamically unfavorable locations.

The sectionalized jacketing does not eliminate the storage problem entirely, as the jacket sections have to be stored too. Also, the rather loose connections between sections sets up the tendency for fluttering which, of course, adds significantly to the effective flow resistance.

It can thus be seen that the various known cables offer larger resistance to fluid flow than the theoretical resistance value, as the geometrical configurations underlying the theoretical calculations are disturbed and distorted locally to a significant extent.

DESCRIPTION OF THE INVENTION

it is an object of the present invention to provide a cable or rope jacket so that theoretically possible, low resistance value can actually be achieved. Also, simple reeling drums for both jacket and cable or rope are to be used.

In accordance with the preferred embodiment of the invention, it is suggested to use two strip-like parts of complementary configuration, each having first flat surface and plane to be placed in abutment with the first flat surface of the respective other strip, and when so placed the now common surface planes define a plane of symmetry. Each part has a second surface, and the second surfaces together define a streamline profile with stagnation points for the flow at exposed lines of jointure of the two strips.

The first surfaces may actually be developed in isolated areas only, as the surface contour is interrupted and provided with recesses, open to the respective first surface, to receive the rope, cable or several thereof such as a rope, a power supply cable and/or signal transmission cable or cables. Together, the mutually facing recesses define an elongated cavity or cavities that extend over the entire length of the assembled jacket.

The first surfaces are additionally provided with fastening means for releasably securing the strips to each other. The fastening means may have construction of plastic zippers established by snap-action grooves and mating ridges for coaction with the ridges and grooves in the respective other strip part. The snap action is to provide some pressure for forcing the parts against each other.

The strip parts may define additional internal cavities for receiving equipment. The parts themselves may be compartmentized to define hollow but closed cavities for obtaining some buoyancy. The semi-fluid-dynamic strip parts are preferably made of an elastic material, preferably plastic. In the case of a skeleton structure for the strips with buoyancy defining cavities, one will preferably use fiber reinforced plastic. In the case of a fiber reinforced plastic, the jacket may have also the function of the load bearing part of an electrical cable.

The recesses for the rope or for the main rope or cable should be provided in the forward portion of the strips (forward in terms of expected position to oncoming flow when assembled and submerged). For example, the principal "load" in the jacket should be in the forwardmost quarter portion thereof. Using one or several cables together with a separate rope in a simple two-part jacket permits rather accurate balancing of the structure. The various ropes and cables can be distributed in the jacket by providing the receiving recesses in the first surfaces, so that the jacketed cable will readily balance in oncoming external flow.

It is pointed out that previously such jacketed cables were invariably of a uniform construction as far as, for example drag rope with power cable is concerned; the cable formed the core for the drag rope. Of course, this configuration can still be used, but the new jacket permits ready adaptation to individual and separate cables. This is particularly advantageous as the several cables, etc., can be arranged along the profile's center line (in cross-section) so that the individual cable and rope elements can be smaller in diameter than is necessary in case of a unitary concentric configuration. That in turn permits the overall construction to be flatter.

DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a cross-section through a jacket for a drag rope with a cable core in accordance with a first example for practicing the preferred embodiment of the invention;

FIG. 2a is an elevation of the surface of one strip element to be used with another as jacket for a rope and for a separate cable in accordance with a second example;

FIG. 2b is a section view along lines II--II in FIG. 2a;

FIGS. 3a and 3b are cross-sections of jackets with internal provisions for different cables, ropes, etc.;

FIG. 4 is a cross-section through a jacketed drag rope with skeleton and compartmentized structure for the two profile parts as joined; and

FIG. 5 is a cross-section through a jacketed cable, wherein the jacket has also the function of a load bearing element.

Proceeding now to the detailed description of the drawings, FIG. 1 illustrates cable and rope jacket parts having configuration of strips 1 and 2 with complementary profile. Each strip has a flat surface 11 and 12, respectively, and the flat surfaces of the two sections abut in the completed jacket. Each strip has a smoothly curved, second surface, 13 and 14, respectively. In the assembled position, the outer surface of the jacket as a whole has streamlined configuration and is symmetrical to the plane of the abutting surfaces 11 and 12 which lie in a common plane. The streamlined configuration is chosen to ensure laminar flow along the outer contour, without separation under the expected flow conditions. The assembled jacket structure offers two joints to external flow. The joints 15 and 16 are disposed in the common plane of symmetry and, thus, they appear in stagnation points of any flow into whose direction the jacket will orient itself when submerged.

The flat surface 11 of strip 1 is provided with two longitudinally extending snap ridges 3 and 5 as well as with a groove in complementary fashion for engagement with a ridge 4 which extends from strip 2. Complementary snap-action (overhung) grooves are provided in part 2 for receiving the bead-like overhung ridges 3 and 5 of part 1.

A semicircular groove is provided in each strip near the respective front of its flat surface and respectively denoted 1a and 2a for the strips 1 and 2. Together, i.e., in the assembled configuration of the jacket, grooves 1a and 2a establish a circular-tubular space which extends along the entire interior of the strips and jacket. A long rope 6 is loosely received in the cavity 1a-2a. A power supply cable 7 or the like is disposed in the interior of rope 6 and constitutes a part thereof. The inner diameter of cavity 1a-2a should be slightly larger than the outer diameter of rope 6, so that any twist in the latter will not lead to binding, but such twist may be eliminated.

The particular construction of FIG. 1 shows the location of the cavities 1a and 2a, so that the center of gravity of the jacket runs through the center line of the resulting circular cavity, so that the center of gravity of the assembled jacket coincides with the center of gravity of the drag rope and of the cable itself. This way, the tendency for flutter is significantly reduced or eliminated entirely.

The particular embodiment of FIG. 1 shows a drag rope as combined with an electrical cable. However, sometimes drag rope and power supply and/or signal cable or cables are furnished separately. In the past, jacketing was quite difficult. As shown in FIGS. 2a and 2b, the invention permits ready accommodation to such plural elements, and establishes a common jacket.

As shown in FIGS. 2a and 2b, the one strip 1' has snap-action grooves 3a-5a and snap-action ridge 4 as before, for connection to a complementary strip 2'. In addition, drag rope 6' and cable 7' are provided and, therefore, positioned separately in separate, semicircular grooves as to each jacket strip.

FIG. 3a shows another configuration as far as using available space is concerned. A cavity such as 8 may be provided to accommodate individual pieces of equipment, such as measuring transducers, etc. These cavities 8 are established by individual recesses in each strip which do not extend over the entire length of the strips and, thus, cavities 8 define individual compartments. FIG. 3a shows also additional snap-action ridges and grooves. Actually, the recesses for the cable 7' are disposed in relation to two ridges and two grooves, so that the cable cooperates in the snap action for locking the two parts 1" and 2" to each other.

FIG. 3b shows how a number of different cables can readily be accommodated, such as a power supply cable 7' and separate signaling cables 10, and they are all separated from the drage rope 6'.

FIG. 4 illustrates a construction on basis of skeleton structure for strip parts 21 and 22. Each part has extensive cavities 9 which may be filled with light material so as to provide some buoyancy to the cable support structure. The cavities 9 may be filled, for example, with some foam material or the like. The strips 21 and 22 are preferably made of glass carbon or metal fiber reinforced plastic, so that the hollow jacket has sufficient strength.

The embodiment shown in FIG. 5 may use also, for example, glass carbon or metal fiber reinforced plastic for the envelope of the cable. The cable jacket itself may serve here as load bearing drag rope.

In each of these cases, it is readily possible to use cables and ropes of reduced diameter and to reduce the profile of the jacket in steps or gradually. It can readily be seen that in each of these embodiments, joints are exposed to the flow only along the center line at leading and trailing edges of the assembled jacket. Thus, the joints (15 and 16 in FIG. 1) appear only on and along stagnation points of flow directed towards the jacket. Therefore, the joints cannot increase the effective resistance coefficient of the structure as based on a smooth contour for a streamlined cross-section.

The jackets can be sectionalized for long cables or ropes if deemed appropriate for reasons of storage. Coupling elements may be inserted in lateral cavities in the section end faces of the jackets to effect a smooth joint between adjacent sections.

It can readily be seen that in each of these embodiments, strip parts such as 1, 2, 1", 2", etc., can be stored on separate drums, and the ropes and cables can be stored on still different drums. Upon pay out and assembly, these drums are reeled separately. The cable or cables and/or rope are run into the respective recesses in what will become the inner interface of the two strip parts. By means of rollers, the ridges such as 3, 4, 5, etc., are forced into the respective mating grooves to obtain the complete jacket. Such a jacket cable may at times be disassembled; for this, the jacket strips are wedged apart, and strips and rope and/or cables as now released are reeled on separate drums.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

Claims

We claim:

1. Jacketing for underwater cables, ropes, drag ropes, etc., with streamline profile comprised of two completely separable profiled strips for individual reeling, each having a first surface to be placed into abutment with the first surface of the respective other first strip and each strip having a second surface disposed symmetrical to a plane defined by the first surfaces when placed in abutment to each other, to establish a streamline profile, resulting joints between the strips as exposed extending along leading and trailing edges of the streamline profile;

the strips each having at least one recess open to the first surface, the recesses having location and contour complementary to each other to define an elongated cavity for loosely receiving the rope or cable when the first surfaces are in mutual abutment;

first fastening means on the strips in the first surfaces thereof for releasably interconnecting the two strips between the cavity and the leading edge of the profile; and

second fastening means on the strips in the first surfaces thereof for releasably interconnecting the two strips between the cavity and the trailing edge of the profile.

2. Jacketing as in claim 1, the fastening means each including overhung ridges and mating overhung grooves in and of the first surfaces and in complementary configuration to each other.

3. Jacketing as in claim 2, the first fastening means including an overhung groove in a first one of the two strips and a mating overhung ridge on the other one of the two strips, the second fastening means including an overhung groove in the other strip and a mating overhung ridge on the first strip.

4. Jacketing as in claim 1, the strips having plural recesses each in the first surfaces thereof to provide plural elongated cavities upon interconnecting the strips to each other, the recesses and resultant cavities extending over the entire length of the strips for receiving plural ropes and/or cables.

5. Jacketing as in claim 4, the recesses defining cavities of different diameters.

6. Jacketing as in claim 1, there being additional complementary recesses in the first surfaces of the strip to define limited space cavities for receiving pieces of equipment.

7. Jacketing as in claim 1, the strips having skeleton construction with closed cavities not open to the first and second surfaces, and providing buoyancy.

8. Jacketing as in claim 7, the closed cavities being filled with a foam.

9. Jacketing as in claim 1, the recesses located so that the center of gravity of the assembled jacket is about the same with or without load bearing cable or rope in the cavity.

10. Jacketing as in claim 1, the strips made of plastic.

11. Jacketing as in claim 10, the strips made of fiber reinforced plastic.

12. Jacketing as in claim 1, the jacket reducing in cross-section throughout its length.