EP0530044A1

EP0530044A1 - Apparatus for sweeping a body of water

Info

Publication number: EP0530044A1
Application number: EP92307873A
Authority: EP
Inventors: William Richard Arthur Allen
Original assignee: Baj Ltd
Current assignee: Baj Ltd
Priority date: 1991-08-30
Filing date: 1992-08-28
Publication date: 1993-03-03
Also published as: AU2200792A; KR930004148A; GB9118600D0; CA2077129A1; TR26422A; NO923317D0; NO923317L

Abstract

A double Oropesa sweep apparatus comprising mine sweeping winch means (21) having two winding surfaces receiving port and starboard kite wires (24,25) respectively to which are attached port and starboard sweep wires (26,27) respectively, each sweep wire having at its outer end a diverter (14,15), a kite (13) suspended by a kite pendant (34) from a point on one of the kite wire/sweep wire elements (12) and a connecting flexible bond (35) connected at one end to a point on the assembly comprising the said one element (12), said kite and said kite pendant and connected at the other end to the other kite wire/sweep wire element (11), preferably by means of a snatch block.

Description

This invention relates to apparatus for sweeping a body of water with flexible elements, hereinafter called cables, at levels between the surface and the bottom. The invention is particularly concerned with mine sweeping but it will become apparent that it could be used for other purposes such as surveying, searching and locating.
Mines are often swept by means of a so called double Oropesa sweep system which employs a single mine sweeper from which a single towing cable leads to a depressor which is a passive guide device or kite which, as the mine sweeper tows the depressor through the water, is pressed down by hydrodynamic forces to hold the end of the kite wire to which it is connected at a distance below the surface which is dependent on the speed of the mine sweeper and the length of cable deployed. Extending laterally from a point on the cable adjacent the depressor, sweep cables (which, in mine sweeping, carry cutters) extend in generally horizontal curves laterally of the line of movement of the mine sweeper to passive diverters which may be of similar construction to the depressor but with their hydrodynamic surfaces extending vertically rather than horizontally. The outer ends of the sweep cables are also attached to the bottom ends of pendant cables to the upper ends of which floats are attached thus maintaining the diverters at a predetermined distance below the surface of the water. Although when the sweep has been deployed there is only a single cable extending from the ship and this cable can therefore be controlled by a single winch, the method of deployment used employs, during the launch process, separate port and starboard wires and an auxiliary winch wire requiring three independently controllable winch barrels. Although this system is satisfactory for use with large mine sweepers it has now been realised that it would be desirable to provide a double Oropesa sweep system which is substantially simpler, lighter in weight and requires less deck space than the system described above.
According to one aspect of the present invention, a double Oropesa sweep apparatus comprises mine sweeping winch means having two winding surfaces receiving port and starboard kite wires respectively to which are attached port and starboard sweep wires respectively, each sweep wire having at its outer end a diverter, a kite suspended by a kite pendant from a point on one of the kite wire/sweep wire elements and a connecting flexible bond connected at one end to a point on the assembly comprising the said one element, said kite and said kite pendant and connected at the other end to the other kite wire/sweep wire element. With this system it is possible to operate a double Oropesa sweep system by means of a single winch although two separately controllable winch barrels may of course be used and may have operational advantages at the expense of simplicity.
In one possible arrangement, the connecting bond, which may be a cable, chain or the like, is connected at said one end to the kite. However, it is preferred for the connecting bond to extend between a point on the said one element, at or closely adjacent to the point of connection of the kite pendant, to the other element. Thus, according to a second aspect of the present invention, a double Oropesa sweep apparatus comprises mine sweeping winch means having two commonly rotating winding surfaces receiving port and starboard kite wires respectively to which are attached port and starboard sweep wires respectively, each sweep wire having at its outer end a diverter, a kite suspended by a kite pendant from a point on one of the kite wire/sweep wire elements, and a connecting flexible bond extending from a point on the said one element at or closely adjacent to the point of connection of the kite pendant and connected at the other end to the other kite wire/sweep wire element. Preferably, in this preferred arrangement the connecting bond is connected to each of the said elements at or adjacent the point of attachment of the kite wire to the sweep wire of the respective element. Preferably the connection at one end of the connecting bond is by means of a snatch block, that is to say a pulley wheel so constructed that it can be attached to and run on a wire at a point intermediate the length of the wire without access to the end of the wire. Preferably the winch means comprises a winch having a single barrel which, in a preferred construction, is divided into two winding sections by a circumferential flange but could alternatively have two separate barrels mounted on a common drive shaft or, for example, on separate drive shafts mounted to be driven simultaneously and at speeds to provide identical winding rates on the two barrels. Alternatively, the winch means could comprise two separate winches arranged to be driven simultaneously and at speeds to produce identical winching rates.
According to a third aspect of the present invention, a mine sweeper carries adjacent its stern a mine sweeping winch comprising a single barrel of which the winding surface is divided into two zones by a circumferential flange, the winch being the sole mine sweeping winch on the mine sweeper. Such a mine sweeper can be used to operate with the double Oropesa sweep apparatus comprised in the first or second aspect of the invention.
The invention may be carried into practice in various ways but these examples of double Oropesa sweep apparatus in accordance with the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:

Figure 1 shows the first example of sweep apparatus deployed from a minesweeper;
Figure 2 shows only the part of the second example of sweep apparatus which is adjacent the minesweeper, the remaining part being identical to that shown in Figure 1; and
Figure 3 shows the same part of the third example, the remaining part again being identical to that shown in Figure 1.

The sweep apparatus shown in Figure 1 of the drawings is deployed from a mine sweeper 10 of which only the stern portion having guard rails 9 is shown. The sweep apparatus includes two kite wire/ sweep wire elements 11 and 12, a single multiplane passive depressor kite 13, multiplane passive diverters 14 and 15 and floats 16 and 17. The mine sweeper carries a simple winch 21 with a single barrel 22 the surface of which is divided in two by a central circumferential flange 23.
Each kite wire/sweep wire element comprises a kite wire 24,25 of 20mm diameter x 550m long steel wire rope and a sweep wire 26,27 of 18mm diameter x 365m long steel wire rope connected together by a swivel assembly 28,29. One end of each kite wire 24,25 is anchored to the barrel 22. The sweep wire 26 of the port cable is left hand lay and the sweep wire of the starboard cable 27 is right hand lay. Each of the sweep wires carries explosive cutters 30 spaced along its length and held in position by mechanical stops provided along the sweep wire and carries a mechanical end cutter 31 adjacent the outboard end. The outboard end of each of the sweep wires 26,27 is connected to the respective diverter 14,15 whose planes are disposed vertically in order to provide a laterally directed force to move the ends of the sweep wires outwardly and away from each other. The depths of the diverters 14,15 are determined by the lengths of the float pendants 32,33 by which the floats 16,17 are connected to the diverters 14,15 respectively.
One end of a wire cable bond 35 is connected at one end to the swivel assembly 29 of the starboard kite wire/sweep wire cable 12 and the other end of the bond 35 carries an openable snatch block 36 through which runs the port kite wire 24. This port kite wire 24 is slightly longer than the starboard kite wire 25 so that the snatch block 36 engages on the port kite wire 24 a short distance ahead of the port swivel assembly 28.
The upper end of a kite pendant 34 is fastened to the swivel link assembly 29 of the starboard kite wire/sweep wire cable 12 while the lower end is connected to the kite 13, the planes of the kite 13 being arranged horizontally so that it provides, as it is drawn through the water by forward motion of the mine sweeper, a downwardly directed force to hold the swivel link assemblies and hence the forward ends of the sweep wires 25 at approximately the same level as the diverters 14 and 15 are held by the floats 16 and 17, the speed of movement of the mine sweeper 10 and the heaving and veering (winding in and letting out) of the kite wires 24 by the winch 21 being adjusted to achieve this result.
It will be noted that the kite wires do not pass over three-roller fairleads at the transom of the mine sweeper as is the usual case with sweeping systems but pass through two fairleads 41 of the hanging pulley block type which are able readily to align themselves with the wire and which have a diameter and groove configuration such as to provide the correct bend radius and full wire support to the kite wires. Davits, not shown, are provided for deploying and recovering the depresser kite and the diverters.
Although the winch has been described in use in a double Oropesa sweep system it will be appreciated that once installed it can also be used for single Oropesa and team sweep systems.
The arrangement shown in Figure 2 is similar to that shown in Figure 1, like parts being given the same reference numerals but with a prime. In the arrangement of Figure 2, the connecting bond 35′ is connected at one end to the swivel assembly 28′ of the port kite wire/sweep wire element 11′ and has the snatch block 36′ at the other end, the starboard kite wire 25′ running through the snatch block. In this arrangement it is the deployed part of the starboard kite wire 25′ which is slightly longer than the deployed part of the port kite wire. This arrangement is of particular advantage where the two barrels of the winch 21 can be controlled independently by contrast with the single winch of the apparatus of Figure 1. With separately controlled barrels, it is possible to deploy the starboard kite wire/sweep wire element 12′ first and pay out a quantity of the kite wire 25′ so that the sweep wire 27′ is deep and the kite wire 25′ enters the water at a steep angle. This minimises the risk of the wires becoming entangled during deployment of the port kite wire/sweep wire element 11′.
The arrangement shown in Figure 3 is again similar to that shown in Figure 1, like parts being given the same reference numerals but with a double prime. In the arrangement of Figure 3, the connecting bond 35˝ is connected at one end by a swivel to the connection between the kite pendant 34˝ and the kite harness. The other end of the connecting bond 35˝ has a snatch block through which the port kite wire 24˝ runs. With this arrangement the depth of the front ends of the two sweep wires 26˝,27˝ can be made the same which is not the case with the arrangements shown in Figures 1 and 2 where the sweep wire connected to the kite will inevitably be slightly deeper in the water than the other sweep wire.
In each of the arrangements shown in Figures 2 and 3, the starboard kite wire 25′,25˝ passes through a device 50′,50˝ having a transducer which detects the tension in the kite wire.

Claims

A double Oropesa sweep apparatus comprising mine sweeping winch means (21) having two winding surfaces receiving port and starboard kite wires (24,25) respectively to which are attached port and starboard sweep wires (26,27) respectively, each sweep wire having at its outer end a diverter (14,15), a kite (13) suspended by a kite pendant (34) from a point on one of the kite wire/sweep wire elements (12), and a connecting flexible bond (35) connected at one end to a point on the assembly comprising the said one element (12), said kite and said kite pendant and connected at the other end to the other kite wire/sweep wire element (11).
Apparatus according to claim 1 wherein the connecting bond (35˝) is connected at said one end to the kite (13˝).
Apparatus according to claim 1 wherein the connecting bond (35,35′) extends between a point on the said one element (12,12′), at or closely adjacent to the point of connection of the kite pendant (34,34′), to the other element (11,11′).
Apparatus according to claim 3 wherein the connection at one end of the connecting bond (35,35′) is by means of a snatch block (36,36′).
Apparatus according to any of claims 1 to 4 wherein the winch means (21) comprises a winch having a single barrel (22).
Apparatus according to claim 5 in which the winch barrel (22) is divided into two winding sections by a circumferential flange (23).
A double Oropesa sweep apparatus comprising mine sweeping winch means (21) having two commonly rotating winding surfaces receiving port and starboard kite wires (24,25) respectively to which are attached port and starboard sweep wires (26,27) respectively, each sweep wire having at its outer end a diverter (14,15), a kite (13) suspended by a kite pendant (34) from a point on one of the kite wire/sweep wire elements, and a connecting flexible bond (35) extending from a point on the said one element at or closely adjacent to the point (28′,29) of connection of the kite pendant and connected at the other end to the other kite wire/sweep wire element.
A mine sweeper (10) carrying adjacent its stern a mine sweeping winch (21) comprising a single barrel (22) of which the winding surface is divided into two zones by a circumferential flange (23), the winch being the sole mine sweeping winch on the mine sweeper.
A mine sweeper according to claim 8 in combination with a sweep apparatus according to any of claims 1 to 7, the port and starboard kite wires being wound on the two zones respectively.