The invention relates to a rectangular frame comprising two parallel positioned framework beams, two transverse beams, and four corners. The invention furthermore relates to the use of such a frame for carrying out work at the bottom of a body of water.

The document JP-59224732 describes a rectangular frame for use on a bottom of water. The frame comprises a bridge part that in its turn comprises a trailing draghead. By moving the bridge part along a set of rails and by subsequently moving the trailing draghead along the bridge, a surface of the bottom of water can be excavated to take bottom samples.

The document DE-2707133 describes a rectangular frame for use on a bottom of water. The frame comprises two parallel positioned framework beams, two transverse beams, and four corners. The frame can move over the bottom of water by alternatingly varying the length of the two framework beams. This way, the frame can move over the bottom of water. The frame also comprises a movable bridge on which an excavation installation can move.

The document NL-8001714 describes a submersible rectangular frame that comprises an excavation wheel. The frame can be equipped with compartments that can be filled with water or air in order to float the frame or submerse the frame to the bottom of water. The excavation wheel is positioned on an arm that can carry out a circular movement with the intersection of the diagonals of the rectangular framework as the centre. The excavation wheel can move over the length of the arm. This way, a circular surface of a bottom of water can be excavated. The frame comprises caterpillar tracks that can move over the bottom of water in order to excavate another part of the bottom of water. This way of dredging offers the advantage that the excavation wheel or the cutter can excavate a clearly defined part of the bottom of water with a high pressing force.

A problem of the use of such a rectangular frame is that this frame has a limited form stability. A small deformation of the frame means that the arm, as described in NL-8001714, can no longer rotate, or that the bridge part, as described in JP-59224732 can no longer move along the rails. Furthermore, when the frame is displaced over a bottom of water with irregularities by means of the caterpillar tracks, the frame will be subject to forces that are such that the frame undergoes a distortion and becomes unusable. The problem of the above-mentioned rectangular frameworks is partially solved by the triangular frame that is described in EP-1544358. This design comprises two heavy triangular parcel frameworks that are movable relative to one another. Both frameworks comprise a leg in the three corners, which is positioned on the bottom of water. The frame can move by alternately lifting the legs of one of the partial frameworks, and by moving this partial frame relative to the other partial frame. The frame comprises an excavation wheel that can excavate the bottom of water. Although this construction has proven itself in a commercially available version, it nevertheless presents a certain number of drawbacks. Moving the triangular frame is cumbersome. Furthermore, the position frame does not offer the possibility of covering a large surface of the bottom of water when compared to a rectangular framework.

The invention relates to a rectangular frame that does not present the described drawbacks of the known rectangular frameworks. This goal is achieved by the following framework. A rectangular frame, comprising two parallel positioned framework beams, two transverse beams, and four corners, in which the extremities of the framework beams and the extremities of the transverse beams are resiliently and by means of ball joints connected to a corner in each of the four corners of the rectangular frame, in which the framework beams, the transverse beams, and/or the corners comprise compartments that can be filled with gas and/or water in order to be able to float the rectangular frame or to submerse the latter into a submersed state.

The applicant has found that, if the rectangular frame comprises the resilient connections and ball joints, the form stability of the frame is increased. By connecting the extremities of the transverse beams and the framework beams resiliently and by means of ball joints to the corners, in each of the four comers six kinematic degrees of freedom may be created. This is an advantage when the frame is moved over the bottom of water. These degrees of freedom ensure that the construction will be less prone to stress, which in turn is interesting for the avoidance of distortion. If this rectangular frame is anchored to the bottom of water by means of vertically resilient supporting means that are connected to the corners, the centre of gravity of this frame shall have six kinematic degrees of freedom. This is an advantage because the reaction forces can thus be taken over in a favourable way when the frame is used to carry out work on or in the bottom of water.

The rectangular frame is furthermore interesting because it can easily be combined with another rectangular frame or with other rectangular frames. The functions of a frame can be supplemented by functions that belong to the adjacent frame. The frame can easily be positioned next to another frame thanks to its geometry.

In this application terminology such as "horizontal", "vertical", "above", "under", as well as terminology derived therefrom, is used for describing the frame according to the invention.

This description should by no means be considered or be interpreted as being limitative, and relates to the frame in its most used situation. Terms such as x, y, z, φ, θ, ψ relate to positions or to displacements, forwards and backwards, laterally, and up and down. The terms φ, θ, ψ relate to angular displacements around the x-, y-, and z-axis.

The term "bottom of water" refers to the floor under a body of water such as the sea floor, river floor and lake floor.

The term "corner" in this description refers to any construction that is suitable for being connected to the framework beams and transverse beams. Preferably, the construction is also suitable for being equipped with supporting means and with anchoring means. The construction for the corners can for example be a boxlike construction or a lattice

construction. Boxlike constructions are interesting because they can possibly be filled with water and gas to float, submerse, or raise the frame. The rectangular frame is preferably submersible. The framework beams, transverse beams, and/or the corners preferably comprise compartments that can be filled with gas and/or water in order to float the frame or to submerse it to reach a submersed position. During the submersion and the raising of the frame thrusters can preferably be used to keep the frame in the desired orientation and to give it sufficient stability.

When the frame is positioned on the bottom of water in the submersed position, the buoyancy of the frame can be increased by pumping water from the compartments. The thus created vacuum shall create upwardly directed force. The water is preferably replaced by a gas. Therefore, the compartments are connected in a closable way to a reservoir that contains a pressurised gas. Such a reservoir is preferably connected to the framework. When the gas from the reservoir is used up, it can be filled by means of a conduit coming from a floating vessel at the water surface. These reservoirs can comprise compartments with a pressurised gas. By using the compartments in an individual way it is possible to deliver a more constant gas pressure to the different systems. These pressure reservoirs can be replaced by new pressurised reservoirs. The used reservoirs can be filled by means of a compressor that is present at the water surface, or can be transported over from the mainland. On the mainland, the reservoirs can be filled with pressurised gas in a more efficient way. The reservoirs with the pressurised gas can also be used to fill the compartments in the framework beams, the transverse beams, the corners, and the movable bridge with gas, as described above. The gas is preferably air but can also be nitrogen or carbon dioxide.

The corners of the rectangular frame preferably comprise means to anchor the rectangular frame to the ground. These means are preferably a screw anchor or a suction anchor. The means to anchor the rectangular frame to the ground preferably comprise an anchor that is situated at the bottom side of a shaft. This shaft is vertically movably positioned in an opening in the corner. Part of the shaft extends above the corner, whereas part of it extends below the corner. The upper end of the part of the shaft that extends above the corner is connected to the corner by means of one or more linear actuators. These actuators can be electromechanical actuators, and preferably hydraulic cylinders. A suction anchor is known as such and comprises a tubular lower part with an open bottom. In principle other forms than a tubular lower part can also be used to create the same effect. Tubular lower parts offer the advantage that the pressure difference between the interior and the exterior of the suction anchors are optimally distributed. By creating an under pressure inside the tubular opening, for example by pumping away the water that is present there, the tube pulls itself as it were into the bottom of water. By reducing the aforementioned actuators, the suction anchor can thus be driven vertically into the bottom of water. A suction anchor is preferably connected to the shaft by means of a ball joint. This is interesting in case of a sloping bottom of water. For harder bottoms of water it can be interesting to equip the lower edge of the suction anchor with a rotatable disc with teeth. This disc can be driven by an engine.

Screw anchors are known as such and usually consist of an axis around which a continuous cutting blade with a certain pitch is wound in the form of a helix. The cutting blade can be equipped with cutting teeth for cutting relatively harder soil types. The screw anchor is preferably driven by an engine with a large torque and a low rotational speed. When the anchor digs into the bottom of water the engine rotates at a speed and with a torque that is suited for the soil type, while simultaneously being driven into the soil by means of the aforementioned actuators with a suitable pressing force. When cutting sand in relatively deep waters, the reaction forces on the cutting blade can become too large due to the created under pressure in the soil at the height of the cutting blades and the fact that water cannot flow to the cutting blades. In a similar situation it is to be preferred that the anchor is a screw anchor that comprises a hollow axis around which a helical cutting blade is positioned, and whereby in the wall of the hollow axis outflow openings are created near the helical cutting blade, openings that are connected to a supply pipe for a gas or a liquid in the hollow axis. A liquid is preferably supplied. This liquid is preferably water that is drawn in at a higher point and that is pumped to the outflow openings by a pump, for example a centrifugal pump. By supplying a gas or a liquid, the creation of a local vacuum is avoided, which would otherwise mean that the anchor would seize up. The corners of the rectangular frame preferably comprise supporting means. Examples of suitable supporting means are a sled, a wheel, or a caterpillar track. The supporting means are preferably resiliently connected to the comers. The supporting means are preferably connected to the corners by means of linear actuators that are adjustable in the vertical direction. By means of these actuators the frame can be positioned in the desired position, for example horizontally, relative to the bottom of water.

The rectangular frame preferably comprises one or more jets, propellers, or thrusters that permit a vertical and/or horizontal displacement of the rectangular frame in a submersed situation, and a horizontal displacement in a floating situation.

The rectangular frame can be used as part of a dredging tool, in a way that is illustrated in the aforementioned published patents DE-2707133, NL-8001714, and JP-59224732. The frame can also be part of a drilling installation, in which the frame comprises a drilling installation, for example as described in US-2012315097, US- 2015021092, WO- 13035038, and WO- 12156742. The frame can also be used to carry out other types of work on the bottom of water, tasks such as laying cables and pipelines, and smoothening the bottom of water, and installing explosive charges on the bottom of water. The form stability of the rectangular frame can be increased by placing one diagonal connection beam or two diagonal connection beams between the corners. Preferably, the diagonally positioned connecting beam is connected to the comer by means of a ball joint and a spring. An interesting way to increase the form stability is by connecting the two framework beams to one or more bridges. This bridge is preferably a movable bridge as will be described hereafter. The rectangular frame comprises a movable bridge that, at both its extremities, is movably connected to the two framework beams, in such a way that a displacement of the bridge in the direction of both transversal beams becomes possible. Such a bridge is interesting because any tool that is connected to the bridge can be moved to any position on the rectangular surface of the bottom of water underneath the frame. These tools can be excavation means as described in the prior art publications, or can for example be a drilling installation. The movable bridge is preferably connected to the transverse beams by means of winch cables that permit the displacement of the bridge. Moreover, winch cables are interesting for the form stability of the rectangular framework. By applying tension by means of the winch cables between the transverse beams and the movable bridge, a frame is created with a high degree of form stability.

The movable bridge at both its extremities preferably comprises a guiding shaft. One of the two parallel positioned framework beams passes through the opening of each of the guiding shafts, which means that the movable bridge can move in the longitudinal direction of the framework beams. The guiding shafts preferably comprise at the inside resilient wheelsets and/or resilient rollers that, during use, confer six kinematic degrees of freedom to the framework beams relative to the guiding shaft. This is interesting for preventing the movable bridge from seizing up during a displacement along the framework beams.

Because the extremities of the framework beams and the extremities of the transverse beams are resiliently connected to a corner in each of the four corners of the frame, the movable bridge will less easily seize up. If such a frame is anchored to the bottom of water the frame is created with a high degree of form stability, whereby the frame also is in possession of six kinematic degrees of freedom. This in turn is interesting when the movable bridge comprises means to work on the bottom of water. The frame can absorb the reaction forces that are created on these means very well when they work on the bottom of water, all the while maintaining the form of the framework. These means are drilling means suitable for exploiting geological formations, as well as excavation means, such as excavation wheels, cutters, drum cutters, trailing heads and/or ploughs. The excavation means can be used for dredging a bottom of water or for excavating minerals from a bottom of water.

The excavation means can be movably connected to the movable bridge. By moving the excavation means along the bridge, and the bridge in the horizontal direction along the framework beams, the rectangular surface of the bottom of water underneath the position frame can be excavated. The movable bridge preferably comprises a row of multiple excavation means. These multiple excavation means are in this embodiment not horizontally movably connected to the bridge. By moving the bridge along the framework beams the excavation means can simultaneously excavate the complete rectangular surface of the bottom of water underneath the positioned frame. Such an embodiment offers the advantage that more soil can be excavated simultaneously. When using certain types of excavation means, such as excavation wheels and drum cutters, it is possible that between the individual excavation means strips remain where the bottom of water has not been excavated. In that case it is preferable to equip the movable bridge with multiple excavation means that are positioned in multiple rows of multiple excavation means, one behind the other, and that the excavation means of a row present an offset relative to the excavation means of the adjacent row. By using the offset of the excavation means, the non-excavated soil will be excavated by the next row. The excavation means are preferably positioned in two rows, one behind the other. The one or more excavation means are preferably connected to a lattice construction that is positioned vertically above the excavation means and resiliently connected to the excavation means to be able to absorb the vertical impact loads on the excavation means and to transfer them to the lattice construction. The lattice construction is resiliently connected to the movable bridge that is positioned vertically above the lattice construction.

Each of the excavation means is preferably connected to a suction tube for discharging the soil/water mixture that is excavated by the excavation means.

The invention shall be further described using the following figures.

Figure 1 shows a rectangular frame (1) with two parallel positioned framework beams (2, 3), two transverse beams (4, 5), and four corners (6, 7, 8, 9). The extremities of the framework beams (2, 3) and the extremities of the transverse beams (4, 5) are resiliently connected to a comer (6, 7, 8, 9) in each of the four corners of the rectangular frame (1) by means of a spring (10) and ball joints ( 1 1). Figure 1 also shows that each of the corners (6, 7, 8, 9) comprises a screw anchor (12) with which the frame (1) can be anchored to the ground. Each corner (6, 7, 8, 9) furthermore comprises a sled (13) and a horizontal thruster (14) as well as a vertical thruster (15).

Figure 2 schematically shows the frame (1 ) of figure 1 , comprising a movable bridge (18). The springs (10) and the ball joints (11 ) are not represented to scale. The sleds (13) are connected to the corner by means of a spring (19) and a hydraulic cylinder (21). The bridge (18) is connected to transverse beams (4, 5) by means of winch cables (20). In this figure the kinematic degrees of freedom of the components that are part of the frame, amongst which are corners (6, 7, 8, 9), framework beams (2, 3), movable bridge ( 18), and sleds ( 13), can be seen. The ball joints (11 ) thereby allow limited angular displacements (cp2, Θ2, ψ2) of the framework beams (2, 3) and the transverse beams (4,5) relative to the comers (6, 7, 8, 9). The displacements of the corners (6, 7, 8, 9) in the horizontal xy-plane due to the compression or extension of spring elements (10) equal X2 and Y2. For the sleds (13) to be able to accurately follow the contours of the bottom surface, kinematic degrees of freedom (x, y, z, φ, θ, ψ) are applied to the sleds. The displacements and the rotations of the sleds (13) subsequently consist of a superposition of the displacements (X2, Y2) and rotations (φ2, Θ2, ψ2) of the corner (6, 7, 8, 9), and vertical displacements (Z4V) of spring (19) and (Z4H) of the hydraulic cylinder (21). Thanks to the kinematic degrees of freedom (x, y, z, φ, θ, ψ) of the sleds (13), the latter can accurately follow the contours of the bottom of water when the frame (1) carries out horizontal displacements over the bottom of water. Moreover, the bending moments in the corners (6, 7, 8, 9) will be greatly reduced by the flexibility of the frame.

Figure 2 also shows that the movable bridge (18) can be moved in the direction (X7) by means of the winch cables (20). The displacements (Y7, Z7) and the angular rotations (φ7, Θ7, ψ7) of the movable bridge (18) are absorbed by resilient wheelsets and/or resilient rollers in the guiding shafts (22), and are further illustrated in the figures 12 and 13.

Figures 3a and 3b show a comer in further detail. To absorb the varying load and/or impact loads on the sleds (13), a spring (19) is clamped in between a plate (25) that is connected to the sled (13), and a plate (31) that is connected to a hollow vertical cylindrical column (33) and a hydraulic cylinder (21 ). A cylindrical guiding tube (26) that is connected to the plate (25) can move vertically back and forth at the inside of the cylindrical column (33). A hollow cylindrical tube (33) can move vertically back and forth at the inside of a tube (35) that is connected to the plates (24, 32). The plates (24, 32) are connected to the corner (8). By means of hydraulic cylinders (21) that are connected to plate (32) which in turn is connected to the corner (8), the assembly of the sled (13) and the hollow vertical cylindrical tube (33) can be moved vertically. To avoid deflection of the cylinder rods (21a) the cylinder rods (21a) are connected to and surrounded by a tube (30) with openings. The tube (30) surrounds the hydraulic cylinder (21 ). An additional advantage thereof is that in case of impact-like or varying loads on the sled, an extra damping is realised by the inflowing and outflowing water through the opening in the tube (30). An interesting method to counter any rotation of the sled (13) around the z-axis consists of using the opposite rotation moment of helical spring (19) that at both extremities is fixed to the plates (25, 31) and/or using a blockage system (not shown in the figure) between plates 31 and 25

Figure 3b also shows a possible embodiment of a means to anchor the frame (1). Screw anchor (12) consists of a cylindrical hollow rigid tube (23) that is connected to two hydraulic cylinders (28) by means of a top plate (27). Around part of the hydraulic cylinders (28) is positioned a water permeable tube (29) that comprises openings, for reasons of inflowing and outflowing of water to facilitate the vertical displacement of the cylinders. The lower part of the tube (23) comprises a rotatably driven screw (12a). The tube (23) can freely move vertically through the corner (8) and is connected to this corner (8) by means of the top plate (27) and hydraulic cylinders (28). The tube (23) can comprise openings for the inflow and outflow of water, to facilitate the vertical displacement of the tube.

Figure 4 shows an embodiment in which corner (40) comprises two sleds (13a, 13b), and in which corner (41 ) comprises two wheelsets (42a, 42b). The directions of movement of the sleds (13a, 13b) and of the wheelsets (42a, 42b) are mutually perpendicular. Dependent on the desired direction of movement of the frame, one of the two sleds or wheelsets per corner is moved upwardly, whereas the other is moved downwardly. Figure 5 shows a corner (43) that comprises a suction anchor (44) that is connected to shaft (46) by means of a ball joint (45). Shaft (46) is connected to the corner at its top end by means of a disc (47) via two hydraulic cylinders (48). Figure 6 shows a corner similar to that of figure 5, with the exception that in this case at the lower part (50) of the suction anchor (51 ) a rotatable disc (52) with teeth is present that will be described in further detail in figures 7a-d.

Figures 7a-d show the suction anchor (51 ) of figure 6 in further detail. Figure 7d shows the disc (52) with teeth, connected to a shaft (53) by means of spokes (54). The shaft (53) is connected to an engine (60). Figure 7c shows the inside of the suction anchor (51), whereby the elements of figure 7d have been omitted. One can see a grid (57) for retaining larger parts of rock or soil, a hollow tube (58) for the shaft (53), a disc (59) that separates the inner space into a top half and a bottom half. A centrifugal pump (61 ) pumps the water out of the bottom compartment. Water can possibly be fed into this compartment via the supply tube (62) and valve (56). In figure 7b the assembly can be seen in its mounted state, whereas figure 7a is an outside view.

Figure 8 shows an interesting screw anchor (65) with a hollow axis (66) around which a helical cutting blade (67) is positioned. In the wall of the hollow axis (66), near the helical cutting blade (67), outflow openings (69) are foreseen. These openings (69) are connected to a supply tube (70) in the hollow axis (66) for a gas or a fluid. Furthermore, an engine (71 ) is present to drive the screw anchor (65) with a suitable torque and angular velocity. A pump (68) is available to supply surrounding fluid to the tube (70). The assembly can be positioned at the bottom side of a shaft (23), as can be seen in figure 3b.

Figure 9 shows a side view of the framework beam (2) and a cross-section A-A of a guiding shaft (22) of a bridge part ( 18). Framework beam (2) comprises at both extremities a ball joint (11). The guiding shaft (22) comprises at its inner side multiple resilient wheelsets (75). Figure 10 shows a cross-section of the framework beam (2) and of the guiding shaft (22) of figure 9, seen in the longitudinal direction. One sees that framework beam (2) consists of three tubes (76). These tubes (76) can independently be filled with water to submerse the frame (1), and filled with air to raise the frame to the water surface. The three tubes are connected to one another by plates (77) to obtain a triangular cross-section. Three resilient wheelsets (75) are equipped with a longitudinal and rotating tube (78) that runs over the exterior surface of the plates (77). Figures 11 and 12 describe the wheelset (75) in further detail. Figure 11 shows wheelset (75) of figure 10 in further detail. The rotating tube (78) can rotate over the angle Θ, and is positioned in such a way that it has degrees of freedom in the radial z-direction and in the tangential y-direction. The wheelset is therefore equipped with springs (79) and (80). The springs (79) support the two bearings (89) of the rotating tube (78). The springs (79) are supported by a movable plate (83) that can move back and forth in the y- direction between two platelets (82) and springs (80) by means of the wheels (81).

Figure 12 shows a wheelset (85) whereby the wheelset (75) of figure 10 in its turn is placed on a moving platform (86) instead of directly on the inner wall of the guiding shaft (22). This platform (86) can turn around its vertical axis over the angle ψ. The platform (86) is connected to the inner side of the guiding shaft (22) by means of a helical torsion spring (87) and multiple supporting wheels (88) that are resiliently suspended from the platform (86).

Figure 13a shows how the corners (6, 7, 8, 9), the framework beams (2, 3), and the transverse beams (4, 5) of the submersible frame (1) are filled with a gas and/or water. Figure 13a shows comer (6) by way of example. By means of an accumulator (A) containing gas under a pressure p2 that is higher than the surrounding pressure pi, the water can, after the pressure regulating valve K5 and valve Kl in situation 1 (Tl) are opened, be expelled from corner (6), for example by a polytropic gas expansion, and via valve K3 be discharged to the

surroundings with pressure pi, after which situation 2 (T2) is reached. By filling the corners (6, 7, 8, 9), the framework beams (2, 3), and the transverse beams (4, 5) with gas, an upwardly directed force is created with which the frame can be transported to the water surface. The different compartments of these parts of the frame can be connected to the same accumulator (A) and/or can each individually be connected to an accumulator (A).

To move from situation 2 to situation 1 (Tl) the gas shall be expelled with the aid of a compressor C driven by engine Ml . The gas will then, after the opening of valve K2, be transported via the non-return valve K6 to the accumulator (A). After the gas has been stored under pressure p2 in the accumulator (A), for example by means of a polytropic compression, the pressure of the remaining gas in the compartment is lower than the surrounding pressure pi , which means that the surrounding water can fill the compartment via valve K3. The remaining gas can be driven out of the compartment via the vent valve K4.

To move from situation 2 (T2) to situation 1 (Tl) it is possible to, in cases in which the compressor C is not functioning, discharge the gas from the compartment via the vent valve K4 using a water pump (PI ), represented in dashed lines, that supplies water from the surroundings under pressure pi after opening valve K7. The complete compartment can thus be filled with water with pressure pi.

To move from situation 1 (Tl ) to situation 2 (T2) is possible to, in cases in which the accumulator (A) and/or the pressure regulator valve K5 and/or valve Kl are not functioning, use the water pump (P2), represented in dashed lines, to expel the water from the

compartment to the surroundings under a pressure that is higher than the surrounding pressure pi .

An alternative way of filling the compartment of comer (6) with water can be found in figure 13b. Thereby, use is made of the water pump PI which, after the opening of valve K6 under a pressure p3, pumps water, in which p3 is higher than the surrounding pressure pi . Possibly, all the gas can be driven out of the compartment via the vent valve K4 or via the compressor C3, represented in dashed lines, via the nonreturn valve K5 to the accumulator (A). To move from situation 1 (Tl) to situation 2 (T2), the water in the compartment can be expelled by using water pump P2 after the opening of valve K7 under a pressure p3 that is slightly higher than the surrounding pressure pi. When the water pump P2 is not functioning, the gas from the accumulator (A) can possibly be supplied to the compartment via the compressor C2 after valve K l is opened under a pressure p3 that is slightly higher than the surrounding pressure, whereby the water can possibly be discharged via the opened valve K3.

Figure 14 shows the frame of figure 1 , with a movable bridge (18) that comprises two rows of excavation wheels (90) that are positioned with a mutual offset. The excavation wheels (90) are connected to a lattice construction (91) that is positioned vertically above the excavation means (90). The lattice construction (91) is connected to the excavation means by means of a resilient connection to absorb the vertical impact loads on the excavation means (90), and to transfer these to the lattice construction (91). The lattice construction (91 ) is resiliently connected to the movable bridge (18) by means of tubes (93) and hydraulic cylinders (94). A suction tube (92) for discharging the soil/water mixture that is excavated by the excavation wheel is connected via bifurcations to each of the excavation wheels (90). The suction tube (92) can be connected to an underwater storage construction, or can be directly connected to a floating vessel at the water surface.