DESIGN FOR TUGBOAT

Abstract: The invention relates to a tugboat (1). The design comprises a towing installation which can turn through 360 DEG in the horizontal plane about a vertical shaft (12). Above the towing installation there is a pilot house (9), and beneath it there are one or more propellers (5). This design provides optimal thrust in all directions in line with the towing cable, in combination with good resistance and swell properties.

Description: Design for tugboat The invention relates to a tugboat The design comprises a towing installaUon which can turn through 360° in the horizontal plane, and beneath which there are one or more propellers This design provides optimal thrust in all directions in line with the towmg cable, in combination with good resistance and swell properties In harbours and restricted sailing areas, ships are usually assisted by one or more tugboats The ship and the tugboat are firstly connected bv cable The tugboat sails with the ship and positions itself in such a manner that it can tow the ship in a specific direction by means of the towing cable Dunng these manoeuvies. it is also possible for a tugboat to be manoeuvred against the ship in order to be able to push it Dunng towmg, there is a cable connection between the tugboat and the ship On board the tugboat, this cable usually runs through a towmg eyelet and is attached to a towing winch or towmg hook The towmg eyelet is arranged as low as possible in the vertical direction on the tugboat, in order to minimize the Ulting of the tugboat and to prevent the tugboat from capsizing With respect to this towing eyelet, the towmg cable can turn sideways through 90° or more m the horizontal plane, towards both boards In the case of a towing winch, the cable length can be adapted to the desired towing length and manoeuvring distance In the case of a towmg hook or attachment point, the towmg cable length is fixed On older models, there is only a winch and a tow g eyelet at the stern, m many modem tugboats, a towmg eyelet and towmg winch are arranged both fore and aft Dunng manoeuvring, the tugboat turns with respect to the ship, but on account of the design of the towmg eyelet, the tugboat can only turn to a limited extent with respect to the towing cable connection. In this embodiment, the towmg installation cannot produce a towmg cable connection m all directions independently of the direction of the tugboat (i e the longitudinal axis of the ship) It is also not possible for the towmg cable to turn through a full 360°, since the towing cable then comes into contact with the deckhouse A tugboat provides propulsion by means of one or more screws Many ships are equipped with two screws positioned next to one another In older models , these screws are positioned aft beneath the ship by means of a propeller shaft. In this case, the thrust is produced predominantly in the longitudinal direction of the ship. This direction is also directed partially sideways by means of rudders. Modem tugboats arc often equipped with so-called thrusters. In this case the entire screw/propulsion unit can turn in the horizontal plane and thrust can be produced in any desired direction. In a number of models, these thrusters are arranged beneath the stem (a so-called azimuth- stem-drive tug), and in a number of models the thrusters are arranged roughly 1/3 of the length from the forward part of the ship (a so-called tractor tug). In all these designs, there is a horizontal distance in the longitudinal direction of the ship between the resultant propulsive force and the direction of the towing cable. In a number of directions (for example the longitudinal direction), this horizontal distance is zero, but in other directions (for example sideways), this distance is relatively great. The optimum towing force is obtained if the resultant propulsive force in the horizontal plane is in line with the direction of the towing cable; for this puipose, therefore, the tugboat always has to adopt the desired position and direction. An exception to this is formed by so-called "dish" designs, i.e. convex, round hull shapes without a clear sailing direction; i.e. the ship can sail both forwards and sideways. In addition, the ship can also turn relatively quickly about its axis. These designs have a small length/width ratio. However, this form of ship has a high resistance, with the result that the design can only reach a moderate speed. During towing, the ship's direction is selected in such a manner that the towing eyelet is positioned in the direction of the vessel which is to be towed. Examples of this include the OMNI 2000 (Robert Allen Ltd) and the Ship Docking Module (SDM) Hvide design (Halter Marine USA). These two designs are distinguished by a flat, shallow hull with one thruster at the front on one board and the other thruster at the stem on the opposite board. Similar designs are based on a roughly round shape with two, three or more thrusters. However, this form of ship has an adverse effect on the resistance of the ship (in particular at increasing speeds), and results in a poor sailing performance in rough seas. In many cases, it is impossible to sail on the sea. Furtheπnore, conventional tugboat designs are aimed at achieving a high thrust at low speed dunng towing, the hull shapes being conventional and unsuitable for reaching (relatively) high speeds. It is clear from this that there are no satisfactory solutions for obtaining the full thrust in lme with the towmg cable, independently of the ship's direction and in combination with good resistance and swell properties. The object of the present αivenuon is to provide an improved device which does not have the drawbacks described above, i.e to obtain full thrust all directions in l e with the towing cable, independently of the ship's direction and in combination with good resistance and swell properties This object is achieved by arranging a towing installation which can tum through 360° in the horizontal plane and can rotate irrespective of the direction of the tugboat This tumable towmg installation may comprise all designs which are known in the pnor art It is possible for a conventional towing winch, possibly in combination with a towmg eyelet, to be placed on a rotatable platform. Another possibility is for a winch drum to be positioned so that it turns around a vertical shaft. The winch drum and towing eyelet may comprise all designs which are known m the pnor art, of numerous forms and dimensions In addition, the winch drum can be dnven in numerous ways. According to another advantageous design, the towing installation rotates about a predominantly vertical connection to a facility for visual observation of the surrounding area. This facility may compπse all designs which are known in the pnor art The facility may comprise a visual recorder which records information about the surrounding area and makes this information available for steeπng the ship In this case, consideration may be given to a camera with electπcal information exchange or an optical installation (with lenses/minors) which transmits light rays The facility may also comprise an (observation) station for one or more people. In this case, consideration may be given to a deckhouse at which one or more people may be stahoned. According to another advantageous design, the (observation) station for one or more people also includes a steering/operating installation for the tugboat According to another advantageous design, the (observation) station for one or more people is positioned at the top side of the vertical shaft, so that the towmg installation can rotate without interference This design produces a low point of action of the towing cable on account of the low position of the towing installation and good visual observation of the surrounding area on account of the high position of the (observation) station. If the steenng/operatmg installauon is also arranged at this (observation) station, it is possible for one or more people to manoeuvre the tugboat According to another advantageous design, the vertical shaft is designed to have a considerable diameter, resulting in a relatively flat drum of large diameter The lower height of the drum produces a lower point of action, with the result that the tugboat is much less prone to capsizing In addition, the flat drum leads to a shorter arm, so that the shaft is better able to absorb the bending moment The large diameter of the drum does result in a rotating couple in the honzontal plane, which has to be absorbed by the tugboat On account of the larger diameter, fewer turns of the towing cable are required, and the cable can be wound up easily without it being necessary to use separate moving guide eyelets. Accordmg to another advantageous design, the drum is provided with a rotating, guiding towing eyelet. The use of a drum with a large diameter allows the rotating towmg eyelet to reduce the capsizmg moment As a result of the towing eyelet also being allowed to turn with respect to the drum by means of a d ve unit, it is possible for the point of action of the towmg force to coincide with the vertical centre axis of the vertical rotation shaft, as a result, there is no rotational couple in the honzontal plane acting on the tugboat If the towing eyelet and the drum together can turn freely, independently of the ship's direction, the drum together with the towmg eyelet will automatically turn towards the object v * hαch is to be towed According to another advantageous design, the vertical shaft is designed as a hollow shaft, with the result that from the (observation) station it is possible to gain access to the hull/mside of the ship, while the towmg installation can turn without obstacle through 360° m the honzontal plane The crew can move without obstacle and safely between the (observation) station and the hull of the ship, where the engines for propulsion are generally accommodated According to another advantageous design, one or more propellers are arranged in the vertical plane perpendicularly beneath or in the vicinity of the tumable towmg installation, in such a manner that the resultant of the thrust can act in the honzontal plane m lme with the towmg cable direction If one propeller is used, it will be aπanged in the vertical plane perpendicularly beneath or in the vicinity of the tumable towmg installation In this way, it is possible for the optimum thrust throughout the entire 360° in the horizontal plane to be realized in line with the towing cable direction by means of the tumable towmg installation. If there are a plurality of thrusters, they will generally be arranged symmetrically with respect to the vertical shaft passing through the towing installation. In this way too it is possible to achieve the optimum thrust throughout the entire 360°. However, at a number of angles there will be a slight loss of thrust as a result of one propeller lying in the flow of the other. According to another advantageous design, the position of the tumable towing installation and the propeller(s) is selected in such a manner with respect to the shape of the ship that the ship's direction follows the thrust direction of the propeller(s). This can be achieved by positioning the propeller(s) half way along the length of the ship or by adapting the shape of the ship in such a manner that a large part of the lateral surface is positioned behind the propeller(s). Additional fins, also known as cutwaters, can have a beneficial effect on this sailing performance, as is already customary in a number of tractor tugs. In this design, after the desired thrust direction has been set, the ship will automatically sail starting from this direction. In this case, the captain can adapt the thrust direction as desired in the customary way. This direction is then set relative to the ship's direction. Another possibility is for the captain to be able to set the desired thrust direction independently of the ship's direction. This so-called absolute thrust direction may, for example, be achieved by relating the direction to absolute North by means of a (gyro)compass. When not towing, the tugboat, after this thrust direction has been set, will automatically sail in this direction When towing, the tugboat, after this thrust direction has been set, will automatically manoeuvre itself into the optimum direction and position with respect to the object to be towed. This design can be used both with a stationary object to be towed and with a sailing object to be towed. In this case, it is also possible for the direction of the steering/operating installation to be selected in absolute terms, so that the orientation of the captain is no longer dependent on the ship's direction, but rather on, for example, absolute North. According to another advantageous embodiment, the tugboat hull shape and the propeller are selected in such a manner that the propeller can produce a high thrust at both low and high speeds and that the hull shape has favourable resistance properties even at relatively high speeds. With regard to the propeller, consideration should be given here in particular to adjustable screws which can produce a high thrust over a _,„,„ 30650 6 wide range of inflow speeds With regard to the hull shape, consideration should be given in particular to a high-speed "aquaplaning" hull shape, in which as the speed increases the ship is lifted out of the water by the dynamic upward pressure and can produce a considerable nse in speed compared to the wave velocity According to another advantageous embodiment, a second towmg eyelet is positioned next to the towing eyelet in the tumable towing installation, above the centre of gravity of the lateral hydrodynamic resistance This second towmg eyelet may be closed, as is the case with a conventional towing eyelet, but may also be provided with an opening, optionally provided with a locking means When using vertical cutwaters, the second towing eyelet will be arranged m the honzontal plane above the latter This design makes it possible, when sailing at reasonably high speeds, to utilize the hydrodynamic lifting force of the cutwater in order to produce an additional towing force According to another advantageous embodiment, two or more cutwaters are positioned at a slight angle with respect to the vertical On account of the mclmed position, the cutwaters predominantly produce a high transverse force, but by specifically selecting the angle of the cutwaters, one or more cutwaters produce(s) a slight upward vertical force and one or more cutwaters produce(s) a slight downward vertical force This vertical couple of forces counteracts the capsizing moment of the towing cable The invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the drawing 1 ., m which Figure 1 diagrammatically depicts a side view of a conventional tugboat Figure 2 diagrammatically depicts a side view of the present invention with a first embodiment of the towmg winch installation Figures 3 and 4 diagrammatically depict side and plan views of the present invention with a second embodiment of the towmg winch installation Figure 5 diagrammatically depicts a cross section illustrating the reduction in the capsizing moment as a result of a relatively flat drum of large diameter Figure 6 diagrammatically depicts the principle of the absolute thrust direction Figure 7 shows front, side and plan views of the present invention for a high-speed hull shape Figure 8 diagrammatically depicts a cross section illustrating the use of mclmed cutwaters for absorbing the capsizing moment of the towing cable Fig 1 shows a conventional twin-screw tugboat 1 having the following components towmg cable 2, towmg eyelet on the aft part 3 of the ship, towing wmch 4, a conventional propeller compnsing two screws 5 arranged next to one another, two propeller shafts 6 and two engines 7 A separate rudder 8 is arranged behind both screws The figure also shows the accommodation 10 for the crew and the deckhouse 9, from which the captain observes the surrounding area and manoeuvres the ship Fig 2 shows the new tugboat design 1, having the following components towmg cable 2, the new towing winch installation compnsing a horizontal platform 11 which turns about the vertical rotation shaft 12 illustrated and. fixedly connected thereto, a towmg eyelet 3 and a towmg w ch 4, as well as two screws 5 positioned next to one another in two thruster units which rum in the honzontal plane, two driving (propeller) shafts 6 and two engines 7 The resultant force from the two thrusters together coincides in the honzontal plane with the towmg cable force passing through the rotation shaft of the towmg wmch installation The accommodation 10 and the (observation) station deckhouse 9 are fixedly connected to the ship by means of the rotation shaft, the towmg w ch installation can turn freely around these parts Furthermore, a cutwater 13 is shown beneath the aft part of the ship Fig 3 shows the tugboat design 1 with a vanant of the towmg winch installation, having the following components towmg cable 2, the cl towing winch installation compnsing a vertical drum, which turns around the vertical rotation shaft 12 shown, of the towmg wmch 4, an optional honzontal platform 1 1 which turns about the same rotation shaft and an opuonal towmg eyelet 3 fixedly connected thereto, and once again two screws 5, two dnv g (propeller) shafts 6 and two engines 7 The (observation) station/deckhouse 9 is once again fixedly connected to the ship by means of the rotation shaft, the towmg w ch installation can turn freely around this shaft Furthermore, a cutwater 13 is shown beneath the aft part of the ship The following three designs exist for the wmch dπve mechanism a) No towmg eyelet- towing wmch drum is dnven and hauls in or pays out the towmg cable b) Towmg eyelet without dπve the towmg wmch drum is dnven as in a), while the towmg eyelet can turn freely about rotation shaft c) Towmg eyelet with combined dπve with towing wmch drum dπve drives tow g eyelet with respect to towmg wmch drum, while both can move freely together around the rotation shaft Fig 4 once again shows the tugboat design 1, in plan view Fig 4a shows the plan view of the deck, Fig 4b shows the plan view of the drum 4 and Fig 4c shows the plan view of the (observation) station/deckhouse 9 In this case, this figure shows the combined dnve of the towmg eyelet 3 fixedly connected on the honzontal platform 11 and the towmg winch drum 4, which can rotate freely about the vertical rotation shaft 12 shown As a result, the tow g cable is directed towards the centre axis of the drum Furthermore, the two cutwaters 13 are once again shown Fig 5 shows a variant of the tugboat design 1 in cross section, with a relatively high drum 14 and a relatively flat drum 4 of large diameter The vertical arm 15 between the thrust and towing cable forces decreases as the diameter of the drum increases Fig 6 illustrates the absolute thrust pnnciple in three steps Fig 6a relates to the situation when towing is not taking place After a thrust direction 16 has been selected, the tugboat will move out of situation (I) via situation (II) towards situation (III), m which the ship is moving in the direction of the thrust Fig 6b relates to the situation with a towmg cable 2 connected to the object 17 which is to be towed After the thrust direction 16 has been selected, the tugboat will descnbe an arc of a circle around the object to be towed, until the thrust direction 16 lies in lme with the rowing cable and the most optimum thrust is achieved The ship's direction is in this case independent of the thrust direction and is determined by the sailing direction towards the optimum towmg position Fig 7 shows the tugboat design with the high-speed hull shape Fig 7a shows a cross section, Fig 7b shows a side view and Fig 7c shows a plan view The shape of the hull can be seen clearly in the three drawings, with a flat bottom aimed at achieving a high vertical dynamic lift, so that the design starts to aquaplane at relatively high speeds The design also shows a second towing eyelet 18 on both sides, vertically above the two cutwaters Fig 8 shows the tugboat design with the inclined cutwaters in cross section The towmg cable 2 pulls on the tugboat and forms a (slight) capsizmg moment The nght-hand cutwater 13 provides a large honzontal component directed towards the left and a slight upward vertical component. The left-hand cutwater 13 likewise supplies a horizontal component and also a slight downward vertical component. The couple of the two vertical components provides a moment which opposes the capsizing moment of the towing cable. Although the invention has been described above with reference to a preferred embodiment, numerous modifications may be made without depaπing from the scope of the present application The tumable towing installation may be ananged at all kinds of positions on the vessel. It is also possible to use all kinds of different forms of thrust and hull shapes.

Claims: CLAIMS 1 Tugboat compnsing a towmg installation which can turn through 360° in the honzontal plane about a substantially vertical connection to an arrangement for visual observation of the surrounding area. 2 Tugboat according to Claim 1, in which the anangement for observation of the surrounding area compnses a visual recorder. 3. Tugboat according to Claim 1, in which the arragenement for observation of the surrounding area compnses an (observation) station for one or more people. 4 Tugboat according to Claim 3, in which the (observation) station for one or more people includes a steeπng/operating installation. 5. Tugboat according to one of the preceding claims, in which the towing installation compnses a winch drum or towing point which turns about a substantially vertical shaft. 6. Tugboat according to Claim 5, in which the visual recorder or (observation) station is positioned at the top side of the substantiality vertical shaft. 7 Tugboat according to Claim 5, in which the diameter of the substantially vertical shaft is greater than half the width of the ship. 8 Tugboat according to one of the preceding claims, which a tow ing eyelet can rotate about the winch drum, and in which the towing eyelet can be turned with respect to the wmch drum by means of a dnve unit, with the result that the point of action of the towing force coincides with the vertical centre axis of the substantially vertical rotation shaft 9. Tugboat according to one of the preceding claims, in which the substantially vertical shaft is designed as a hollow shaft 10. Tugboat according to one of the preceding claims, in which one or more propellers are arranged in the vertical plane beneath or in the vicinity of the tumable towmg installation, such that the combined thrust can act in the honzontal plane m/in the vicinity of an extension of the towing cable, by means of the towmg mstallation 1 1 Tugboat according to one of the preceding claims, in which the tumable towmg installation and the position of the propellers are selected in such a manner with respect to the tugboat hull that, as a result of the direction of the thrust being selected independently of the ship's direction (a so-called absolute direction), the tugboat, when sailing freely, automatically begins to sail in this thrust direction, and the tugboat, when towmg, automatically manoeuvres into the optimum direction and position with respect to the object which is to be towed 12 Tugboat according to one of the preceding claims, in which the hull shape and propeller are selected in such a manner that the tugboat produces a high thrust both at low speeds and at high speeds, and the hull shape has favourable resistance properties even at relatively high speeds 13. Tugboat according to one of the preceding claims, in which a second towing eyelet is provided in the vertical plane above or in the vicinity of the centre of gravity of the lateral hydrodynamic resistance 14 Tugboat according to one of the preceding claims, in which two or more cutwaters are arranged at a slight angle with respect to the vertical, in such a manner that the vertical dynamic couple of forces of the cutwaters counteracts the capsizing moment of the towing cable.

Inventors: M VAN DER LAAN, M. VAN DER LAAN
Applicants: IMC CORPORATE LICENSING BV, M VAN DER LAAN, M. VAN DER LAAN
Application year: 2000
Main classification: B63B35
IPC codes: B63B21, B63B35