| P A T E N T C L A I M S 1. Sweeper for the collection of impurities in the sea, comprising two extended forward sidewalls (7) with floating elements (8) along the upper edge and weight elements (9) along the lower edge, where the sidewalls are arranged in a V-shape that converges toward a collection area from where the unwanted impurities/ materials on the surface can be collected and be removed, characterised in that a wall-forming body (6) is arranged in the collection area in a largely vertical position between the two extended sidewalls (7), where the inclined position is in a downward and backward direction, where the two rear sidewalls (2) with the floating elements (3) along the upper edge and the weight/sinking elements (4) along the lower edge are arranged in an inverse V-shape that diverges from the wall-forming body and forms a defined backwater area (11) from where the impurities are removed. 2. Sweeper according to claim 1 , characterised in that the wall-forming body (6) is a stretch-resistant cloth of a flexible material which, when the sweeper is in use, is forced against the inside of the forward sidewalls (7) and forms the wall- forming body (6) in the collection area. 3. Sweeper according to claim 1 , characterised in that the side edges (6a,6b) of the crosswise placed wall element (6) are fastened to respective insides of the cloth faces (7a, 7b). 4. Sweeper according to claim 1 , characterised in that the cloth faces (7a,7b) extend on each side some distance below the lower horizontal edge side 6b of the wall element. 5. Sweeper according to claim 1 , characterised in that the cross-wise wall element (6) has a trapezoidal shape with the smallest part on top and the widest part at the bottom. 6. Sweeper according to claim 1 , characterised in that a reinforcing line is placed between the underside of the two cloths and is fastened in the chain links 9 and 4, respectively, and defines a crosswise chain run 67. 7. Sweeper according to claim 1 , characterised in that a cross section space (66) that is bordered by the crosswise chain run 67, the inner sides (7a, 7b) of the cloth and the underside (6b) of the wall element define a channel opening (66) through which the oil/water mixture can flow from the upstream side of the sweeper in front of the wall element and to the downstream side (backwater area) behind the wall element. 8. Sweeper according to claim 1 , characterised in that to provide that the cloth sides that face forwards towards the stream 10 are bent from below and at an incline outwards as a consequence of the incoming stream of water (cf. figure 2), the towlines 104a, 104b are set up to be coupled at the lower edge of the forward part of the cloth (1 19,121), such as to the ends of the lower chains. 9. Sweeper according to claim 1 , characterised in that the wall-forming body 6 comprises a mat (140) of a thicker material and comprises a wall element-forming part (42/6) and side sections 43a,43b that are set up to be fastened to the inside of the cloth sheets 7a, 7b in the forward direction. 10. Sweeper according to claim 1 , characterised in that the cloth mat is made of flexible rubber, and preferably strengthened by a reinforcing material which is built into the rubber material. 1 . Sweeper according to one or more of the preceding claims, characterised in that a net (1) is arranged in the bottom of the sweeper as a continuation of the wall-forming body (6), said net (1) allows chemicals to flow through upwards into the backwater flow between the two rear sidewalls (2). 12. Sweeper according to one or more of the preceding claims, characterised in that it is built to be towed by only one vessel which uses a paravane (51) in one of the forward ends of the chain yoke (9) and the sidewalls (7) to keep the sweeper displaced sideways with respect to the course of the ship, and also that the forward part of the sweeper extends out and is open in the forward direction towards the inflowing body of water. 13. Sweeper according to one or more of the preceding claims, characterised in that it is built so that the under-pressure zone is kept open and in a correct form with the help of a stretch from paravanes (52) fastened to the rear end of the chain yokes (4) and sidewalls (2). 14. Vessel for collection of impurities in the sea, comprising a hull construction set up to concentrate and collect impurities and water from the sea surface, characterised in that the vessel is shaped as a two-hulled catamaran vessel where the internal and facing hull sides of the hulls have a corresponding surface design as the inside of the sweeper according to the claims 1-11 , and also that they together with a crosswise placed wall-forming element (6) define an approximate X-shape in plane outline. 15. Vessel according to claim 4, characterised in that the sides of the hull on each side of the element (6) extend some distance below the lower, horizontal edge side 6b of the wall element. 16. Vessel according to one of the preceding claims 14-15, characterised in that the crosswise placed wall element (6) has a trapezoidal shape with the smallest part on top and the broadest part at the bottom. 17. Vessel according to one of the preceding claims 14-16, characterised in that the cross section (66) that is bound under the element (6) and the lower edges of the hull parts, defines a flow cross section for a channel opening (66) through which the oil/water mixture can flow from an upstream side in front of the wall element and to a downstream side (backwater area) behind the wall element. 18. Vessel according to one of the preceding claims 14-17, characterised in that the forward hull sides in front of the element (6) define a V or approximate U shape that converges towards the element (6) from which the unwanted impurities/polluting material on the surface can be collected and removed. 19. Vessel according to one of the preceding claims 14-18, characterised in that the two sides of the hull that face each other upstream of the element (6) define faces that run downwards in an incline and inwards towards the underside of the hull, while the sides of the hull downstream of the element (6) define faces that run in an incline downwards and outwards towards the underside of the hull. 20. Vessel according to one of the preceding claims 14-19, characterised in that the underside of the hull is covered by a plate which, together with the two sides of the hull, define a closed channel that is open at the front for inflow of liquid and at the rear for outflow of liquid, and the plate is in particular a double- walled keel part which can be formed with a tank to hold the impurities that are collected by the vessel. 21. Vessel according to one of the preceding claims 14-20, characterised in that the crosswise placed element (6) is made with a fold (150) that forms a triangular shape the pointed end (155) of which is in the forward direction towards the incoming stream of water (13). 22. Method to collect unwanted materials on the surface of water, characterised in that a sweeper according to one or more of the claims 1 -6 is towed, or built into, a suitable vessel operating at an appropriate speed so that the unwanted material is led into the collection area and is forced down alongside the wall-forming body and from the lower edge of the body flows up into an area at the rear of the body in the collection area. 23. Method according to claim 22, characterised in that the unwanted material is pumped up from the rear side of the body in the collection area by a pump and is led away, either to a tank in said vessel or to a separate collecting sausage. 24. Application of the sweeper according to one or more of the claims 1-6 to remove chemicals, such as oil, from the sea surface. |
The present invention relates to a new construction of a sweeper for the collection of impurities in the sea, comprising two extended forward sidewalls with floating elements along the upper edge and weight elements along the lower edge, where the sidewalls are arranged in a V-shape that converges towards a collection area from where the unwanted impurities/materials on the surface can be collected and be removed, as described in the introduction to claim 1 . It also relates to a vessel for the collection of impurities in the sea, comprising a hull construction set up to concentrate and collect impurities and water from the surface of the sea as given in the introduction of claim 14.
The invention also relates to a method and an application to collect unwanted material on the surface of water.
With the invention, one aims to provide a tool to collect chemicals, and in particular, oil that floats in layers on the surface of the sea as a consequence of unintentional discharges, such as in different forms of ship breakdowns or leakages in connection with the exploration of oil.
One also aims to make a construction that can concentrate and collect oil layers from the surface of the sea, i.e. both at open sea and in calmer waters near the shore. The expression sweeper is used about an appliance to collect and retain the oil layer which floats in towards a V or U shape, for example, when it is towed behind one or more vessels or is stretched out in a polluted stream of water. The expression boom is used about appliances that are extended out in the sea to block off an area, for example, a coastline and the like, so that this does not become polluted. A sweeper that is used in the present context is also described as a skimmer or an oil trawl.
Prior art
In the known oil booms, the oil is led in and collected at the bottom which forms a V or U shape. From this area, the oil is sucked up with the help of a skimmer or other suction equipment. It is a well known problem that much of the oil that is brought together slips out under the lower edge of the boom and out into a turbulent backwater downstream to the rear of the sweeper, and with no possibility of being satisfactorily collected and handled.
There are also known booms that are constructed with cross-wise placed, stiffer wall surfaces which are set up across the inflowing oil so that a bow wave and different forms of flow loops are formed in front of the wall. This leads to the oil, as a mixture of the pure layers and mixed into the body of water, being pulled down and under the lower edge of the wall and into a turbulent flow area at the rear of the wall. The oil is retained in this area as a typical backwater with turbulent flows, and one collects the oil from this area with the help of a skimmer. An example of such a construction is known from Norwegian Patent 166.659. However, this construction is very complex as it is composed of three distinct separate boom sections arranged one after the other, and the collection part itself which defines a chamber, is made up of a stiff housing part that is towed after a float link.
One of the major disadvantages of this construction is that it is a stiff tool which is hampered in its movement in the sea and the waves. The filling of water in front of the boom when it is being towed will also force the boom down and in an outwardly direction which in turn leads to a downward flow along the boom walls, and there the oil will be forced down and under the wall of the boom, as indicated in the figures 1 and 2. It is only smaller parts of the oil layer which will float into the narrow channel-forming guiding body, with a larger fraction ending up on the outside. Another disadvantage is the complex construction of the boom, with ropes, crowfeets and towlines causing disadvantages. The only similarity to the new, present construction is that we take up the oil in the backwater area. The backwater effect is in itself known, but the whole of the collecting and guiding of the oil pollution to the bow wave, below the bow wave, into the turbulence area and further up into the backwater is a novelty. The whole system is built up completely differently and this is also a novelty.
According to the present invention, it is an aim to be able to lead the oil into a backwater area where it is collected and held, in that an under-pressure zone is formed and reinforced at the rear side of the sweeper cloth. Then, one collects the oil from this backwater area.
The principle which is applied in the present invention is as follows: In front of any body that moves forward in the water, a bow wave is formed where the water is stationary and builds up immediately in front of the bow, glides downwards and forwards and down in the layer which is formed between the stationary bow wave and the water the body passes. There, oil is lost in existing oil booms, while, according to the present invention, one controls the movements of the oil here towards the backwater so that it can be collected. In the concave V-shape behind the body, a strong suction will arise as the volume of the area must continuously be refilled. The oil that comes to the rear in the layer is controlled by the suction straight into the V-shape and remains there until it, according to the present invention, is removed, preferably by being pumped up or with the help of skimmers or the like.
The specific gravity and centrifugal force are the central regulating factors, but the buoyancy of the oil can also be of help. Thus the sweeper can also be used for other unwanted materials that float. A reference to the invention is inserted here when the patent claims are finished. The sweeper according to the invention is characterised in that a wall-forming body is arranged in the collecting area in a largely vertical position between the two extended sidewalls, where the inclined position is in a downwards and backwards direction, where two rear sidewalls with floating elements along the upper edge and weight/sinking bodies along the lower edge are arranged in an inverse V-shape that diverges away from the wall-forming body and forms a defined backwater area from where the impurities are removed. The body is preferably a stretch resistant cloth of a flexible material which, when the sweeper is in use, is forced against the inside of the forward sidewalls and forms the wall-forming body in the collecting area. The side edges of the crosswise placed wall element are fastened to the respective insides of the cloth surfaces.
It is preferred that the cloth surfaces extend on each side some distance below the lower horizontal edge side of the wall element. Furthermore, the crosswise placed wall element can have a trapezoidal form with the smallest part uppermost and the widest part at the bottom. A reinforcement line can be inserted between the underside of the two cloths and fastened in the chain links, and can define a crosswise stretch of chain.
The cross-section space that is bordered by the crosswise stretch of chain, inside surfaces of the cloth and the underside of the wall element, preferably defines a channel opening which the oil/water mixture can flow through from the side upside of the sweeper in front of the wall element and to the downstream side (backwater area) behind the wall element. To ensure that the sides of the cloth that face forward towards the current are bent downward and outwardly in a slant as a consequence of the incoming flow of water, the towlines are arranged to be connected to the lower edge of the forward part of the cloth, such as to the ends of the lower chain links.
The wall-forming body comprises a mat of a thicker material and comprises a wall element-forming part and side sections that are set up to be fastened to the inside of the cloth sheets in a forwardly direction. The cloth mat is from a flexible rubber, and is preferably strengthened with reinforcing material which is built into the rubber material.
A net-formed cloth can be arranged at the bottom of the sweeper as a
continuation of the wall-forming body through which net chemicals can flow up to the backwater flow, between the two rear sidewalls. The sweeper is constructed to be towed by one vessel only that uses a paravane in one of the forward ends of the chain yoke and the sidewalls to keep the sweeper displaced sidewise in relation to the course of the ship, and also that the forward part of the sweeper is extended and is open in a forwardly direction towards the incoming body of water. Furthermore, it is constructed so that the under-pressure zone is kept open and in a correct shape with the help of a stretch from the paravanes fastened to the rear end of the chain yoke and sidewalls.
The vessel according to the invention is shaped as a two-hulled catamaran vessel where the internal and facing hull sides of the hulls have a corresponding surface design as the inside of the sweeper according to the claims 1-1 1 , and also that they together with a crosswise placed wall-forming element (6) define an approximate X-shape in plane outline. Furthermore, preferred embodiments of the vessel are given in the subsequent dependent claims 15-21.
The method according to the invention relates to a sweeper, according to one or more of the claims 1-6, being towed by or being built into, a suitable vessel operating at an appropriate speed so that the unwanted material is led into the collection area and is forced down alongside the wall-forming body and from the lower edge of the body flows up into an area at the back of the body in the collection area. Preferred embodiments are given in claim 21. According to the invention the sweeper and the vessel are used to remove chemicals, such as oil, from the sea surface.
Short description of the figures.
Embodiments of the invention shall now be described with the help of examples, where reference is made to the enclosed drawings, in which: Figure 1 shows an actual application of the sweeper that is towed behind a vessel and held stretched out with the help of paravanes.
Figure 2 shows a plane outline seen from the front, of the sweeper according to the invention.
Figure 3 shows a side outline of the sweeper in figure 2.
Figure 4 shows a vertical section of the sweeper seen from the front in towards the crosswise-placed body according to the invention.
Figure 5 shows the sweeper and the flow conditions seen from above.
Figure 6 shows the sweeper and flow conditions in a vertical side section. Figure 7 shows a solution of a chain yoke for the sweeper.
Figure 8 shows a side perspective of an emergency vessel with a sweeper function built-in according to the present invention. Figures 9A, 9B and 9C show a plane outline, an end outline and a perspective outline of a preferred embodiment of the oil emergency vessel according to the invention.
Figure 10 shows the sweeper according to the figures 1-4, seen from above with a strong cloth installed as the wall-forming body 6 and a strong connection between the forward sidewalls 7.
Figure 11 shows the reinforced insertion part of the cloth from figure 7 in an unfolded condition.
Figure 12 shows a side outline of the offshore sweeper that shows how the strongly reinforced cloth 6 is fitted as a wall-forming body 6, as a solid connection between the sidewalls 7 and inclining down towards the connection of the chain yoke.
Detailed description of the invention,
As can be seen in the figures 1-4 the sweeper 100 is constructed with forward and rear pairs 2a, 2b and 7a,7b, respectively, of cloth walls which in a middle section are connected via a crosswise, vertically arranged wall element 6 so that the construction forms an X-shape. When the sweeper is towed forwards in the sea the wall element 6 is set crosswise and the forward cloth walls 2a,2b are extended at the front, tilting out to the side. But one can also regard the construction as two longitudinally running cloth sheets 2a, 7a and 2b,7b that are set up to adjoin and are folded in the middle via the crosswise placed wall element, as is illustrated in figure 2. Figure 1 shows a vessel 50 that tows the invented X-shaped sweeper 100 through the sea 102 in the direction of the arrow 10, to collect oil or other polluting materials that float on the surface of the sea 102, and is shown by the arrow 13. The sweeper 100 is towed via two towlines 104a and 104b where the one towline 104a is connected directly to the one forward end 119 of the sweeper. The other line 04b is connected to the other forward end 121 of the sweeper via a paravane 51 which ensures that the whole of the sweeper is displaced sideways in relation to the course of the ship, and also that the forward part of the sweeper is extended and is open in the forward direction. Thus, the construction can be pulled by one single vessel. The forward 7 and rear 2 sidewalls are kept afloat at the top edge with the help of floats 8, 3 and held down in the sea at the lower edge with the help of weight elements/chain yokes 9, 4.
The sidewall 7a of the sweeper 100 which is lying nearest the vessel 50 is somewhat longer than the forward sidewall 7b which is placed furthest away from the vessel 50, but one shall not be limited to this as the two sidewalls can be the same length.
The ends of the two rear sidewalls 2a and 2b are also connected to their own paravane 52 to spread out the rear cloth walls into a V-shape, and are completely independent of whether one uses one or two vessels to tow the sweeper. Chains
53, 54 are also running between the forward and the rear sidewalls 7, 2 which contribute to hold them extended at the right angle during the towing, and to establish said X-shape. The angle of the V-shape between the two forward extended sidewalls 7a, 7b can be around 40 degrees. The sidewalls are made from a compact cloth material, such as from a reinforced plastic canvas or net so that they are light and do not take up much space during storage. The wall element 6 is also made from a compact and strongly reinforced cloth material, or has a partially flexible plate shape, such as from plastic or metal (aluminium).
During use, the crosswise placed body 6 will be bent backwards by the pressure from the incoming water so that it tends to form a concave surface side that faces forward towards the incoming water/oil stream.
Detailed construction of the sweeper.
Figures 2, 3 and 4 show details of the construction of the sweeper 100 with two extended cloths 7a, 2a and 7b, 2b, respectively, which are interconnected approximately in the middle by a crosswise placed, vertical wall element 6.
Respective weight elements/chain yokes 9,4 are secured to the lower edge of the cloth along the whole of its length, while the upper edge comprises floats 8,3. When the cloth walls are extended out into the sea, the sweeper forms said approximate X-shape with the side of the cloths upstanding, or slanting outwards as will be explained in the subsequent text. Explained in a different way, the forward facing cloth sides 7a,7b extend in a slope outwards in separate directions towards the incoming flow of water and form a V-shape. Correspondingly, the paravanes contribute to that the sides of the cloth that are facing backwards also extend out backwards and form a V-shape, and together, these sets of cloth can be seen to form said X-shape.
The two towlines 104a, 104b are set up to be connected at the points 119 and 121 , respectively, at the lower edge of the forward part of the cloth, i.e. to the chain yokes 9,4. The towlines are only connected at the lower edge (1 19 and 121 , respectively) of the forward cloth ends, i.e. to the ends of the lower chains, and preferably not to the upper cloth ends. This is so that the sides of the cloth shall be bent from below and out into an incline as a consequence of the incoming flow of water (cf. figure 2).
As shown in figure 4, the crosswise wall element 6 has a trapezoidal shape as it is smallest at the top and widest at the bottom. The cloths 7a and 7b are fastened adjoining the two sloping side edges and extend some distance below the lower horizontal edge side 6b of the wall element. A reinforcing line (steel wire or chain) is inserted between the underside of the two cloths and is fastened to the chain links 9 and 4, respectively, and defines a chain stretch 67. As a reinforcement, reinforcing lines (steel wire/chain) are arranged around the whole of the trapezoidal shape that is defined by the two parallel reinforcing lines/sides 66, 67 and the cloth sides 7a,7b. The open cross section 66 below the element 6 constitutes the space that oil/water flows through from the front and out at the rear side of the wall.
Furthermore, from the one upper corner of the wall element a slanting second reinforcing line (steel wire/chain) 71 is arranged forwards and down in a crosswise direction to a fastening in the longitudinally running weight element 9. The cloth surface 7b is fastened to this second crosswise placed reinforcing line 71 and defines a folding line 71 so that the cloth over and under the line 71 is bent outwards. Seen in a vertical section, the cloth thus forms a V-shape about the folding line 71 in the longitudinal area which in figure 2 is marked L (between the line 53 and the wall element 6) as both the cloth parts slant/tilt outwards about the fold 71. A corresponding crosswise placed reinforcing line is fastened to the opposite cloth surface.
Furthermore, the length extension of the longitudinally running weight element (steel wire/chain) 9 between the point 75 where the crosswise running chain stretch 153 is fastened to the weight element 9 and the rear end of the weight element longer than the corresponding float extension lying above.
As a consequence of the tension to which the construction is subjected to during towing by the vessel 50, the forward 51 and the two rear 52 paravanes, the two cloths at the rear end of the sweeper will be set to slant outwards down from the top.
As mentioned previously, the two towlines 104a, 104b are set up to be connected to the sweeper at the points 119 and 12 , respectively, at the lower edge of the forward part of the cloth, i.e. to the chain yokes 9,4. During towing, the two cloth surfaces 7a and 7b in front of the wall element 6 will therefore be bent outwards by the incoming flow of water 13. When the sweeper is pulled through the sea, the oil on the surface will concentrate and form a thicker layer and be forced under the lower edge 6b of the wall-forming element 6 and then move up towards the surface again in a backwater 11 immediately behind the body 6, where it is very concentrated and can easily be collected.
This backwater effect can be reinforced in that a plate or cloth 5 is fastened to the bottom edge 67 of the body 6 and runs horizontally and extends some distance back from the plate 6 as is shown in figure 6.
The forward sidewalls 7 of the sweeper are gradually higher to the rear towards the dividing element 6, while the rear sidewalls 2 of the sweeper preferably have an even height. A net 1 , see figure 6, can be set up below, or from, the lower part of the cloth 5, i.e. as a horizontal extension from the body 6, between the two rear sidewalls to catch seabirds and any flotsam that follows the oil under the body, while it lets through the oil.
Figure 5 shows the sweeper seen from above to illustrate the current conditions when oil and water flow in through the sweeper. The figure shows a unit for the sucking up of the oil from the backwater 11 through a hose 18 with the help of the pump 15, to pump the oil to a storage vessel (not shown). Floats 16 are shown that keep the pump 15 in place. Also shown is how the chain elements from the two rear sidewalls 2a, 2b are connected with the chain 54 to limit the extension of the cloth. The arrows 3 show how oil/water flows in the funnel form and is concentrated, with the oil layer lying above being collected in a thicker layer. The round arrows 17a, 17b shall illustrate the oil/water mixture which is forced up along the outwardly slanting cloth surface to bend upwards and inwards toward a centre shown by 17c. A layer 22 is formed around the bow wave and which is pulled down under the wall element 6 by the wake of water. That the inlet is gradually becoming narrower also contributes to this effect which results in a thicker layer of the lighter oil up to the bow wave in front of the crosswise wall 6.
Figure 6 shows the sweeper seen from the side. Here it is shown clearly that the sidewalls have become deeper/higher, i.e. that they lie deeper in the water, from the front and back towards the wall-forming body 6. After this they have the same height. The arrow 10 shows the direction of towing. The floats 3,8 lie on the surface of the sea and keep the sweeper afloat. The oil layer in the surface of the sea water 23 approaches the wall-forming body 6 and is forced to glide down 22 and under the wall-forming body 6. A cloth 5 can be fastened from the lower edge of the wall-forming body 6 and horizontally backwards so that the oil can not start moving up again before it has passed this cloth. This cloth 5 at the bottom can reinforce the calm of the under-pressure zone, as it dampens the turbulent streams in the backwater area. The oil moves then in around the rear edge of the cloth 5, where the oil is pressed on the inside so that concentrated oil is sucked up in the backwater area 1 1. The oil can therefore be collected through the hose 18.
It is indicated in the figure that the pressing down of the oil film starts at the point 22 and it continues in an arch shape down under the body 6, possibly along the underside of the approximately horizontal plate/cloth 5, to turn up and forwards on the top side of the plate/cloth 5 and further upwards towards the backwater area 1 1.
The wall-forming cloth body 6 is shaped to be set vertically in the sea. The angle 20 between the wall-forming body 6 and the cloth 5 can be about 90 degrees. The cloth 5 is preferably parallel with the water surface 23. According to a preferred embodiment, but not shown in the figures, a wave breaker can be set up between the two forward sidewalls 7 in front of the wall-forming body 6. The wave breaker can encompass floats with a cloth fastened to the rear side and to the sidewalls 7 on both sides. Any water on top of the cloth can be drained off by an opening immediately in front of the wall-forming body 6. This is to calm the sea up to the wall element 6 so that the oil remains in one layer on the surface, and is not homogeneously spread out in the swirling water waves. This also prevents that splashes of water get into the oil in the under-pressure zone.
Figure 7 shows alternatives to how the chain yokes to the sweeper can be arranged. Figure 7 shows the chain yokes that follow along the underside of the forward sidewalls 7 and the rear sidewalls 2, and can also be connected at the back with a steel wire running across at 54, and at the wall-forming body 6 shown by 6b in figure 4.
The wall-forming body 6 can preferably be strengthened by a reinforced cloth that is tightened when the sweeper is in use. The body can be, according to an alternative embodiment, a plate made from plastic, or from a light metal
(aluminium) or a composite material. But it is preferred that the plate is strong, light and can be folded up. Similarly, the floating elements along the upper edge of the sweeper and the sinking elements along its lower edge can be of the different types known to a person skilled in the arts. The floating elements are preferably floats. The weight/sinking elements are preferably chains, which form weight elements and at the same time are used to tow the whole of the sweeper, but steel wires can also be used. The float capacity is adjusted to the chain weight so that the sidewalls lie correctly upright or in an inclined position in the sea. The chains are connected as chain yokes and the chain yoke will then distribute the towing force to the whole cloth system so that one avoids large point loads. The under-pressure zone is held open with the help of sideways pulling with the help of paravanes at the rear end of chain yokes and sidewalls 2 as shown in figure 10.
The sweeper needs a relatively large vertical stretch to hold its correct form during the towing. Because of that it is preferred that a yoke of chain weight adjusted to the need is fastened to the bottom of the sweeper, i.e. to the points 119 and 121 , respectively, at the forward, lower edges of the cloths and that the whole system is towed in this yoke. The cloths will then incline naturally outwards during the towing.
The middle section of the sweeper, that is the wall-forming body 6 in its inclined position between the two extended sidewalls, is as mentioned broader at the bottom in relation to the top, see figure 4, to prevent that the under-pressure sucks the sidewalls towards each other during the towing. Thereby, the chain yoke stretches the under-pressure area open. This gives a broader lower edge and a more controlled turbulence in the under-pressure zone. Above the middle section the width is adjusted to the pump which is applied.
If the unwanted material on the sea surface that shall be collected is to be pumped onboard into one or more of the towing vessels, the pump hose, umbilical, electrical cables to the pump and any air hoses can be placed alongside one or both, preferably one of the extended sidewalls and the chain yoke. For limited discharges, for example, less than 1000 cubic meters, the oil is preferably pumped directly to tanks of the oil emergency vessel in this way. For larger operations, the material, for example oil, can be pumped if required directly over to a transfer sausage so that the oil emergency vessel can be utilised optimally. The sweeper according to the present invention has mainly two application areas to which it can be adapted: use in open waters and use in protected waters such as harbour areas, and the like. For use in open waters one will normally use the sweeper as described above, which is as a large and solid sweeper that can withstand relatively high seas and cover large areas, that is towed by one or more vessels.
The invention structured into an oil protection vessel.
In smaller and more protected waters, such as sheltered waters, harbour areas, coves and lakes, it is preferred to use a smaller sweeper that is built into a vessel as is shown in the figures 8, 9, 9A and 9B, although a larger towed sweeper can, of course, also be used. The vessel is formed as a catamaran vessel, the underwater hull of which is formed approximately as the mentioned X-shape of the sweeper that is shown in figure 2. The two hulls define a relatively wide inlet 13/37 and the hull sides 170a, 170b taper back to a crosswise arranged body that defines a backwater area at the rear. The vessel comprises pumping equipment with hoses to remove the oil from the backwater area 31.
This vessel is then a stand in vessel fitted with its own propulsion system which will quickly collect impurities in the sea, as it must not be set out on the sea, in contrast to a larger sweeper, or be connected to a towing boat, and it is also easy to handle in narrow and shallow waters.
Figure 8 shows such a stand in vessel with the surface contours of the sweeper built into the hull. The hull 29 itself is formed as a catamaran with an outwardly extending V-form at the front and a diverging concave V-form at the rear part of the hull 35. It can also have wings 30 that can unfold at the front on both sides. The control cabin 28 is preferably placed immediately above the under-pressure zone 31 and is fitted with a window in the deck for the monitoring of the pumping process.
The crosswise placed wall-forming element 6 defines, together with the hull sides 120a, 120b and 170a, 170b, respectively, (figure 8) a vessel hull with an X-shape in a plane outline. On each side of the element 6, the hull sides extend some distance below the lower horizontal side edge 6b of the wall element. The wall element is arranged as a mainly vertical, downwardly extending plate between the hull parts. According to the invention the underside of the hull is covered by a plate 167 which together with the two hull sides 120,170 and the "tunnel roof 166 define a closed channel which is open at the front for inflow of liquid, and at the rear for outflow of liquid, and in particular, the plate is the upper part of two double-walled bottom plate keel parts 167a, 167b which can be made with one or more tanks 32/34 to hold collected impurities. In this part of the hull, propulsion equipment can also be located with propellers 172, one on each side.
Furthermore, the crosswise placed element 6 can be made with a fold 150 that has the same vertical height and which forms a triangular shape, the pointed end of which is directed forward towards the incoming flow of water 13/17c.
As for the towable sweeper, the crosswise placed wall element 6 can have a trapezoidal shape as it is smallest at the top and broadest at the bottom.
Furthermore, the cross section 66 that is bound under the element 6 and the lower edges of the hull parts defines a flow cross section for a channel opening 66 through which the oil/water mixture can flow from an upstream side in front of the wall element, and to a downstream side (backwater area) behind the wall element. Used in a vessel as shown here, the plate element 6 can also have a square or rectangular plane outline shape.
The forward hull sides 170a, 170b in front of the element 6 define a V-shape which diverges forward toward the incoming stream of water 13. Furthermore, upstream of the element 6 the hull sides 170a, 170 that face each other define surfaces that run in an incline downwards and inwards towards the underside of the hull, while the hull sides downstream of the element 6 define surfaces that run in an incline down and out towards the underside of the hull.
The underside of the hull is covered by a plate which together with the two inwardly facing hull sides defines a closed channel which is open at the front for inflow of liquid, and at the rear for outflow of liquid.
Figure 9a shows a plane outline of the vessel. To regulate the operating depth, there must be sufficient ballast capacity in the tanks 32. The vessel can be fitted with tanks 33 for storage of the water with the polluting materials, which is pumped up. The pump is preferably installed floating in the under-pressure zone 31 behind the plate 6. A downwardly running, rigid, permanent or movable plate 6 is placed between the catamaran hulls, that leads the impurities down into a turbulent area 31 in front of the plate 6 and then down under the plate.
In the emergency vessel with the functions of the sweeper built in, the wall- forming body is a part of the hull of the vessel and is then preferably made from a stiff material such as steel, aluminium or fibre glass or the like.
Alternative construction of the wall element in a towable sweeper.
According to a preferred embodiment that is shown in figures 10 and 11 , a wall- forming body 6 is first made as a mat 140 of a thicker cloth where the bottom and top are in parallel, while the sidewalls slant outwards. The mat is composed of the central wall element 42/6 and the side sections 43a,43b which are set up to be fastened to the inside of the cloth sheets 7a, 7b. The side sections 43a,43b have the approximate same height (vertically) as the cloth sheets 7a,7b and will stretch some distance forward on the inside of these. The cloth mat is preferably of a flexible material, such as rubber, and is reinforced with wires or chains. These can advantageously be built into the rubber and are shown as dotted lines 44.
When the mat is installed in the sweeper, it is folded about the shown folding lines 41 and is fastened to the already existing cloth 7 on the inside as shown in figure 10, so that the mat section 42 forms the wall-forming element 6 with a shape approximately as shown in figure 2, while the side sections 43 are fastened to the inside of the forward cloth sidewalls 7 on both sides. The side sections 43 of the mat 140 will then reinforce the sidewalls 7 also. It is preferred to place
strengthening/reinforcing rope, chains or steel wire on the inside of the cloth, the outside of the cloth (between the cloth and the sweeper) and on the outside of the sweeper in the fold 41. This strengthens the fold further and provides anchoring points where the cloth can be secured to the cloth faces of the rest of the sweeper. The mat 140 is secured, glued, welded or vulcanised, preferably permanently, as an integral and reinforced part of the central unit of the sweeper that forms the wall-forming body 6. Alternatively, the reinforced cloth can also be fastened so that it can be removed, or inserted according to need, and the cloth will then be forced against the sweeper by the incoming flow of water during towing so that it is held in the right position.
Figure 10 shows this sweeper seen from above with such a cloth installed as a wall-forming body 6 towed by two vessels 40. Figure 12 also shows the sweeper with such a cloth installed, seen from the side. Here one can see how the slanting position of the folds 41 leads to the parts 43 also slanting so that the rear part 42 which forms the wall-forming body is set vertically. A vulcanised net can preferably be fastened by the vertical lines 46, 47, 48 and 49 to reinforce the sweeper. When the offshore sweeper is built with such a flexible cloth mat 140 installed as a wall-forming body 6, the whole of the sweeper is still flexible so that it can be spooled in its entirety and be stored on a drum. The preferred embodiment of the offshore sweeper is then relatively simple to put out to sea and be taken up again onto the towing vessel, something that simplifies the operation.
Example of a preferred embodiment of the invention.
The size of the sweeper can, of course, vary a lot, according to what one wants to use it to collect and under what conditions it shall be used. According to an example, the forward sidewalls 7 are about 150 m long, while the rear sidewalls are about 10 m long.
The speed of the water stream under the sweeper at 4 knots is 2 m/sec and the speed of water 1 m from the centre of the vortex that is formed at the rear edge of the wall-forming body 6 is then:
Diameter 2 m x 3.14 x ¾ of the circumference, giving a water speed of 4.7 m per second.
The oil can not pass through such a vortex. The centrifugal force forces the oil into the centre of the vortex and up into the backwater and here it stays as long as the vessel is towing and creates an under-pressure. Both the floating capacity of the oil and the centrifugal force have positive effects. Thus, a 4 m deep sweeper can hold large amounts of spilled oil waste which is led from the area in front of the wall element 6 and into the rear in the backwater area.
For example, if we pull a 60 meter wide sweeper along the edge of an oil spill that has an average oil thickness of 1 mm, 60 cubic meters of oil will be collected per 1000 meters (1000 m x 60 m x 0.001 m). For one half hour at a speed of 3 knots this corresponds to 167 cubic meters (1852 m x 3 knots x 60 m x 0.5 hour x 0.001 m) of oil being collected and at 4 and 5 knots 220 and 278 cubic meters, respectively, will be collected. The oil will, of course, not remain in the sweeper but be sucked up continuously with the help of a pump.