WO2000050698A1

WO2000050698A1 - Excavator for subsea excavation

Info

Publication number: WO2000050698A1
Application number: PCT/NO2000/000055
Authority: WO
Inventors: Trond Hystad
Original assignee: Hystad, Leif, Arne
Priority date: 1999-02-22
Filing date: 2000-02-15
Publication date: 2000-08-31
Also published as: AU2833700A; NO990817D0; NO990817L; NO309335B1

Abstract

An excavator/digging unit for installation aboard a vessel (12), whereby the aims are great reach of the digging bucket, great lifting strength of the boom work (10) and very good stability conditions aboard the vessel (12) supporting the digging unit. For these purposes the boom work (10) has two longitudinal, parallel boom arms (14), each at a distance outside the adjacent side of the vessel, and which are supported jointly pivotal at the rear. At their opposite end portions, the two longitudinal boom arms (14) are connected to each other by means of a transversal yoke (22), on which the bucket (18) is supported. The yoke (22) is centrally provided with at least one bracket (24) for a hoisting rope (26), which leads to a hoisting winch (28) through a guide means (20; 30) positioned ahead of the bow and above the deck level at the top of a davit-like post (32).

Description

Excavator for subsea excavation.

This invention relates to a sea-based excavator carried and moved by a surface vessel or another floating unit, said excavator comprising a boom work pivotal at one end about a transversal axis, and carrying, at the other end, a digging bucket arranged to pivot itself, in addition to following the pivotal movements of the boom work.

The sea-based excavator is constructed with a view to performing submarine digging operations, for example moving masses on the sea bed from one location to another and for loading masses on/from the sea bed, for example in connection with dredging, building of piers etc.

Primarily a great (deep) reach and great lifting capacity are aimed at, while, at the same time, the aim is to provide a very stable, in particular laterally stable, digging unit, in which the deck dimensions of the surface vessel have been optimally exploited with a view to the reach, strength and stability of the digging unit. Said objects are realized, according to the invention, by a sea-based excavator formed in accordance with the features appearing from the preamble of claim 1, and exhibiting, in addition, the features stated in the characterizing part of claim 1.

The pivotal boom work of the sea-based excavator comprises two essentially parallel, longitudinal boom arms, connected at the front at the digging bucket by a transversal yoke, on which the digging bucket is supported, pivotal about an axis parallel with said yoke, whereas right astern the essentially parallel, longitudinal boom arms are pivotally supported, preferably by a common transversal axle extending parallel to the pivotal shaft of the digging bucket.

For the pivoting and lifting capacity of the digging unit, said transversal yoke is provided with at least one bracket for a hoisting rope, which leads to a powerful hoisting winch.

For maximum utilization of the deck dimensions of the surface vessel, with the intention of increasing the lateral stability, lifting capacity and general strength properties of the digging unit, the pivot of the boom work is positioned right astern, whereas a guide disk for the hoisting rope is positioned above deck level, at or somewhat in front of the frontmost point of the vessel. The boom work with supporting device, bucket and hoisting winch is positioned so that it all becomes mirror-symmetrical about a vertical plane through the central longitudinal axis of the vessel. In the contracted idle position of the digging unit, roughly speaking only the digging bucket and immediately adjacent portions extend beyond the contour of the vessel.

The excavator according to the invention is preferably mounted on a powerful, manoeuvrable boat of great engine power, for example in the form of a tugboat.

The digging bucket may have, in a manner known in itself, forward-pointing teeth. The pivoting of the bucket itself relative to, for example, the boom arms, may with advantage be implemented by means of piston cylinders/telescope cylinders driven by pressurized fluid, or by other extendable/contractible actuators, whose one axial end is jointed to the transversal yoke of the boom work, and whose other axial end is jointed to the rear wall portion of the digging bucket.

The very substantial, longitudinal extension of the very elongate, pivotal boom arms favours the reach of the digging unit, the lifting force having been left to one or two hoisting winches, the hoisting rope end(s) thereof being secured centrally to a bracket (brackets) on the transversal yoke of the boom work. This simplifies constructions considerably compared to the use of fully or partly submerged driving devices.

An upper guide disc for the hoisting rope may with advantage be mounted at the top of a post/davit positioned at the frontmost point of the vessel, so that the guide disc is located at a suitable height above the deck of the vessel. Such a positioning of the guiding disc(s) for a hoisting rope (hoisting ropes) leading to a winch and with a free end (free ends) to said bracket(s) on the transversal yoke of the boom work, provides the boom work of the digging unit with a large pivot angle and thereby great lifting height/reach, counted from the support at the stern of the vessel and the location of digging operations on the sea bed.

The digging bucket may conveniently be provided with a movable lid which actuated when mass is displaced inside the bucket. Such a lid, which may advantageously be hydraulically manoeuvrable, provides the advantage that masses containing a lot of small particles are prevented from being whirled up.

By a moderate moving distance for the mass, a digging unit carried by a boat may work without the assistance of barges. Masses from the sea bed may possibly be delivered ashore and be used in fillings, pier constructions etc.

The sea-based excavator according to the invention is particularly suitable for the displacing of masses and levelling of the sea bed.

The sea-based excavator according to the invention is easily operated by one operator.

A sea-based excavator according to the present invention may be detached from the surface vessel by disengagement of the connection between the excavator and the stern of the vessel by the common pivot axle of the two boom arms.

The digging unit has a great digging capacity for most types of masses that will be encountered in submarine connections. In particular is achieved an optimal utilization of the capacity of the digging unit in connection with loading and moving masses deriving from blasted rock.

In a typical case the boat may have a length of 30 metres, a width of 8 metres; depth reach: 4 metres; propulsive force 15-20 tons, thruster 2-5 tons, bucket volume 12-15 m³, winch arrangement: minimum 30 tons; intervals 5 - 7 minutes (dependent on transport); capacity about 150 m³/hour (working depth 0-20 metres).

A non-limiting example of a preferred embodiment is explained in the following with reference to the accompanying drawings, in which:

Fig. 1 - 3 show side views of a sea-based excavator according to the invention, carried by a surface vessel, whereas Fig. 4 shows the same vessel with the digging unit, in a top plan view;

Fig. 1 illustrating the digging unit in its active position with the digging bucket in a position of digging, relative to mass on the sea bed;

Fig. 2 showing the digging unit in a position of transport, in which the bucket with mass is oriented with its opening facing upwards;

Fig. 3 corresponding to Fig. 2, but showing the bucket in a discharging position, oriented in a downward slope; Fig. 4 illustrating the boom work of the digging unit, essentially corresponding to the position according to Fig. 2.

As appears in particular from Figs. 2-4, a digging unit, generally identified by the reference numeral 10, carried by a surface vessel, has a longitudinal extent somewhat exceeding the length, e.g. 30 metres, of the vessel 12.

The vessel-supported digging unit 10 comprises a very elongate boom work consisting of two essentially parallel rigid boom arms 14, Fig. 4, extending in the longitudinal direction of the vessel 12, and pivotally supported astern by a transversal, common axle 16 with an essentially horizontal axis, a supporting point optimally selected with respect to the reach of the digging unit. A factor limiting this reach is that the digging bucket 18 should be allowed to be lowered and hoisted through a point 20, which is not too far ahead of the bow.

Just ahead of the bow, the two longitudinal boom arms are connected through a transversal yoke 22 which has a central o bracket 24.

From the forward bow portion and positioned at a relatively steep forward slope, is arranged a post 22, formed, positioned and oriented with a view to a favourable point of attack at the boom work in the lowering, hoisting and 5 retaining in transport position above the sea surface.

The front sloping edge of the post 32 may extend, for example, at the same angle to a horizontal plane, as the bow itself. At its upper free end, the post 32 carries a guide disc 30 for a hoisting rope 26, whose one end is secured to the bracket 24 on the transversal yoke 22, Fig. 4, and whose other end leads to a hoisting winch 28. Of course, two winches may be arranged, their wires each running across a respective one of two preferably parallel, coaxial guide discs 30 arranged at the top of a wide, common post, and the free ends of the wires leading to a bracket each, corresponding to 24, equally spaced from the central point of the transversal yoke 22.

The bucket 18 has forward-pointing teeth 34 and is pivotally supported between two V-shaped arms 36, whose one ends are rigidly secured to the transversal yoke 22 of the boom work, and whose other ends are jointed to the sides of the buckets. The pivot shaft of the pivoting of the bucket itself, at the end of the pivoted boom work 10, is identified by 37.

Two parallel hydraulic piston cylinders 38, extending in the longitudinal direction of the boom work and placed mirror- symmetrical to a vertical plane through the central longitudinal axis of the boat, are jointed by their axial ends, partially to the transversal yoke 22, partially to the rear wall of the bucket 18.

The mode of operation of the sea-based digging unit/excavator may be understood through an examination of Fig. 3 in connection with Figs. 1 and 2, the discharging position shown in Fig. 3 being advantageous in the lowering of the bucket to a location of work on the sea bed 40, where the bucket 18 is brought into a position of attack opposite the mass 42. As a consequence of the simple configuration of the digging unit, the unit may easily be detached from the vessel, so that the latter may be used for other types of assignments.

Claims

C L A I M S

1. An excavator for installation aboard a surface vessel (12), for example a tugboat, said excavator comprising a boom work (10), which is pivotally supported at one end, and which carries, at its other end, a digging bucket

(18), c h aracter i z ed in that the boom work (10) comprises two elongate essentially parallel boom arms (14), which extend in the longitudinal direction of the vessel, and have, at a support point astern, a transversal preferably common axle (16), and are connected to each other at the front, somewhat ahead of the bow, by means of a transversal yoke (22), on which the bucket (18) is pivotally supported, either directly or indirectly, and which carries at least one bracket (24) for a hoisting rope (26), leading across a guiding means (20, 30) at the bow of the vessel (12) and above deck level to a hoisting winch (28).

2. An excavator according to claim 1, c har ac t eri z ed i n that said guiding means (20), in the form of a rotational guide disc or similar wheel-like disc (30), is supported at the top of a post (32), which slopes steeply forward from a position at the bow.

3. An excavator according to claim 2, c h a r a c t e r i z e d i n that the post (32) is sloping forwards, from the bottom upwards, essentially corresponding to the corresponding slope of the bow of the vessel.

4. An excavator according to claim 1, 2 or 3, c h ar ac t e r i z ed i n that the digging bucket (18) is pivotally supported (37) at the front ends of preferably V-shaped arms (36), whose rear ends are connected to the transversal yoke (22) of the boom work, and that to the rear wall of the bucket (18) and to said yoke (22) are jointed drivable, extendable/contractible actuators, for example in the form of hydraulic piston/telescope cylinders (38), for the pivoting of the bucket (18) about its pivot shaft (37) relative to the boom work (14,14,22).

5. An excavator according to any one of the preceding claims, c h ar ac te r i z ed i n that the bucket (18) is oriented, as in a forward digger, in the digger unit.

6. An excavator according to any one of the preceding claims, c h ar ac te r i z ed i n that from its end at the rear pivotal support and to its opposite end, where the two boom arms (14) are connected through a o transverse yoke (22), either boom arm (14) is formed by a rigid, non-articulated, long, narrow element.

7. An excavator according to any one of the preceding claims, c h ar ac te r i z e d i n that the digging unit itself, including the boom work (10), bucket (18) 5 and the driving means/piston cylinders (38) of the bucket, has only one securing point, right astern on the vessel ( 12) .

8. An excavator according to any one of the preceding claims, c har a c t e r i z e d i n that the digging unit is formed so that in its installed, active position aboard the vessel (12) it is mirror-symmetrical about a vertical central plane through the longitudinal axis of the vessel.