GB2075085A - Apparatus for cutting trenches - Google Patents

Abstract

A trench can be cut in a ground surface with jets of pressurised fluid emitted from nozzles (3). The nozzles are mounted such that their positions can be changed together in the vertical direction without changing their relative inclinations. For use in cutting sea bed trenches the nozzles (3) may be mounted via a parallelogram linkage (4 to 9) beneath an underwater tracked vehicle, and water jets may be pumped through the nozzles. <IMAGE>

Description

SPECIFICATION Apparatus for cutting trenches This invention relates to apparatus for cutting trenches in ground surfaces, particularly seabed or other underwater ground surfaces.

It is known to cut trenches in seabed surfaces, for cables or pipelines or the like, with apparatus having nozzles connected to a pump system for producing relatively high pressure high velocity water jets. With this known arrangement the efficiency of removal of material from the trench depends on the direction and velocity of the water jets on impact thereof with the seabed surface, and, in order to achieve high efficiency for a particular surface material and trench size, it may be necessary or desirable to ensure that the positioning of the nozzles relative to such surface is appropriate to the production of the requisite water jet impact parameters.

An object of the present invention is to provide trench-cutting apparatus with which the positioning of nozzles thereof relative to a ground surface can be readily and conveniently adjusted to enable efficient removal of ground material to be effected for a range of different materials and trench dimensions.

According to the invention therefore there is provided apparatus for use in cutting trenches in ground surfaces, comprising a plurality of nozzles, and pressurising means for feeding pressurised fluid to the nozzles to be emitted as jets therefrom, characterised in that, said nozzles are mounted so that the positions thereof can be collectively vertically adjusted without changing the relative inclinations thereof.

With this arrangement, the positioning of the nozzles can be readily and conveniently adjusted, so as to enable operating conditions appropriate to the efficient removal of ground material to be achieved for a range of different materials and trench dimensions.

Most preferably, there are a plurality of different sets of nozzles and these are interconnected so as to be movable downwardly simultaneously so that the heights of the sets are independently adjustable to give a stepped configuration of variable steepness, but without changing the angular dispositions of the sets relative to each other. Thus, the sets of nozzles may be mounted on substantially horizontal supports and a parallelogram linkage may be used to achieve simultaneous vertical displacement thereof whilst maintaining their horizontal dispositions. In this way efficient stepwise cutting and material removal can be achieved.

In order to facilitate material removal, suction tubes may be mounted alongside the nozzles, such tubes acting to pick up material displaced by the nozzles and to eject same at some convenient location remote from the trench being cut.

Preferably, the said nozzles are mounted on a vehicle, so that trench-cutting can be effected as the vehicle is advanced over the ground surface. In one embodiment, the vehicle is a tracked vehicle having a pair of tracks with the said nozzles disposed therebetween.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic side view of a tracked vehicle provided with sets of water jet nozzles in accordance with one embodiment of the present invention; Fig. 2 is a transverse sectional view of the arrangement of Fig. 1; Fig. 3 is a side view to a larger scale of the sets of nozzles of Figs. 1 and 2; and Fig. 4 is a diagrammatic perspective view of one of the sets of nozzles of Fig. 3.

Figs. 1 and 2 show an underwater tracked vehicle, having a pair of tracks 1, 2 respectively along opposite sides thereof. For a more detailed description of the vehicle and particularly the construction of the tracks thereof reference is made to our co-pending Application of even date.

Between the tracks 1,2 as best shown in Fig. 2, there is mounted an assembly 3 of water jet nozzles which are connected via flexible pipes (not shown) to a water jet pump. The assembly also incorporates suction tubes 4, 5, 6, 7 which are connected via flexible conduits 7a to dredge pumps 7b.

In more detail, and as best shown in Figs. 3 and 4, the assembly 3 comprises four vertical square section said tubes 4-7 which are arranged in a row in spaced apart side-by-side disposition. The tubes 4-7 are interconnected by two pairs of parallel rigid elongate links 8, 9, one pair on each longitudinal side of the row of tubes. The links 8, 9 of each pair are spaced one above the other and are respectively level with the links of the other pair. The tube 4 at one end of the row is much taller than the other three tubes 5-7 which are of a common height, and the links 8, 9 are connected at one end to a bracket 10 on the tube 4 so as to be pivotable relative thereto about horizontal axes.

The other tubes 5-7 have flanges 11 thereon which are pivotally connected to adjacent positions on the links 8, 9.

A hydraulic actuator 12 is connected between (and is pivotally mounted relative to) the tube 4 and the links 8, 9 so as to be capable of effecting pivoting of the links relative to the tube. During such pivoting the tubes 4-7 remain vertical and the links 8, 9 remain parallel to each other, the links 8, 9 and tubes 4-7 defining a parallelogram linkage. The links 8, 9 are pivotable between an uppermost position, as shown in Fig. 3, at which the links extend horizontally and the bottom ends of the tubes 4-7 lie in a common horizontal plane, and a lowermost position as shown in Fig. 1 at which the links 8, 9 are inclined downwardly at an angle and the tubes 4-7 adopt a stepped configuration.

The tallest tube 4 is mounted on an underframe structure of the tracked vehicle so as to be vertically slidable relative thereto and a hydraulic actuator 1 3 is connected between such structure and the tube 4 for effecting such sliding.

To each tube 4-7 there is secured a pipe arrangement (see Fig. 4) comprising two side-byside upright L-shaped pipes 14 which are joined at upper vertical end portions thereof to a common inlet pipe 1 5 and which are interconnected by transverse linking pipes 16, 1 7 at lower horizontal end portions 20 thereof. Nozzles 18, 19 are provided beneath the said lower horizontal end portions 20 and also below the said transverse pipes 16, 17. The nozzles 18, 19 lie in a common horizontal plane substantially level with the bottom end of the tube 4, 5, 6, 7. There are six nozzles in all (four beneath the pipes 16, 17 and two beneath the ends 20 of the pipes 14) and these may be directed vertically downwardly or at an angle as desired.With one arrangement, four vertically directed nozzles 18 are provided beneath the pipes 16, 17 and two inclined nozzles 19 are provided beneath the pipe ends 20, such nozzles 19 being inclined at angles of 450 towards each other. Reinforcing struts 21 are provided between the lower horizontal end portions 20 and upper vertical end portions of the pipes 14.

In use, the tracked vehicle can be advanced along an underwater seabed surface with the nozzle sets retracted, that is with both actuators 12, 13 in the uppermost positions thereof. In order to cut a trench in the seabed, all sets of nozzles are lowered with the actuator 13, and the actuator 12 is operated to pivot the links 8, 9 downwardly so that the sets of nozzles adopt a stepped configuration as shown in Fig. 1. The water jet and dredge pumps are operated whereby material is blasted away from the seabed by relatively high pressure high velocity water jets emitted by the nozzles 18, 19, and dislodged material is sucked up through the tubes 4-7 and blown away from the trench being cut as the vehicle advances.

With this arrangement, each set of nozzles is at a position in relation to the seabed surface appropriate to the efficient removal of material thereby. That is, each set of nozzles efficiently blasts material from the seabed at its respective depth (down to the level of the next lower set of nozzles) and spoil produced is removed by the respective suction tube 4-7 or, alternatively (and particularly in the case of large stones), transferred to the vicinity of the next lower set of nozzles.

The operational position of the actuator 12, and hence the steepness of the stepped sets of nozzles, is selected in accordance with the desired trench depth and the nature of the seabed material. Thus, for estuary-type mud, the action of the water jets is to cut deep narrow slots, the resulting spoil being readily removable by the suction tubes 4-7, and the nozzle sets may be set relatively steeply. For a sandy seabed the water jets act to remove a larger volume of material giving a wider trench and for which a less steep inclination of the nozzle sets is required.

It will be noted that positional adjustment of the nozzle sets to suit requirements can be effected quickly and conveniently, simply by operating the actuator 12, and the action of the parallelogram linkage is such as to ensure that the predetermined inclinations of the nozzles relative to each other and to the seabed surface are maintained during such adjustment.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are f described by way of example only.

Claims (10)

1. Apparatus for use in cutting trenches in ground surfaces, comprising a plurality of nozzles, and pressurising means for feeding pressurised fluid to the nozzles to be emitted as jets therefrom, characterised in that, said nozzles are mounted so that the positions thereof can be collectively vertically adjusted without changing the relative inclinations thereof.

2. Apparatus according to claim 1, wherein there is a plurality of different sets of nozzles and these are interconnected so as to be movable downwardly simultaneously so that the heights of the sets are independently adjustable to give a stepped configuration of variable steepness, but without changing the angular dispositions of the sets relative to each other.

3. Apparatus according to claim 2, wherein the sets of nozzles are mounted on substantially horizontal supports.

4. Apparatus according to claim 3, wherein a parallelogram linkage is used to achieve simultaneous vertical displacement of the sets of nozzles whilst maintaining their horizontal dispositions.

5. Apparatus according to any one of claims 1 to 4, wherein suction tubes are mounted alongside the nozzles.

6. Apparatus according to any one of claims 1 to 5, wherein said pressurising means comprises a water jet pump.

7. Apparatus according to any one of claims 1 to 6, wherein the said nozzles are mounted on a vehicle.

8. Apparatus according to claim 7, wherein the said vehicle is a tracked vehicle.

9. Apparatus according to claim 8, wherein the said tracked vehicle has a pair of tracks and the said nozzles are disposed between same.

10. Apparatus according to claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.