EP1268267A1

EP1268267A1 - A floating arrangement and methods related thereto

Info

Publication number: EP1268267A1
Application number: EP01925592A
Authority: EP
Inventors: Sune Georg Axelsson; Folke Vidar Axelsson; Claes Arnold EKSTRÖM
Original assignee: ASCE Ltd AB
Current assignee: ASCE Ltd AB
Priority date: 2000-04-05
Filing date: 2001-04-02
Publication date: 2003-01-02
Anticipated expiration: 2021-04-02
Also published as: FI20000805A; NO20024820L; FI20000805A0; DE60107823D1; FI109463B; ATE284808T1; WO2001074655A1; AU2001252292A1; NO20024820D0; EP1268267B1

Abstract

The present invention relates to a method at attaching a floatable device (8) to a hoisting member (1) and, respectively, releasing the device from said member, wherein a point (10) at said hoisting member (1) is brought by means of separate floating means (11) into such a position in relation to the floatable device (8) that a connecting secondary hoisting member (1c) can be attached with a slack. The present invention further relates to a method for releasably connecting a floatable device (8) to a hoisting member (1), wherein said floatable device (8) and separately provided floating means (11) are maintained in a mutually generally horizontally centered disposition in order to achieve said slack. The present invention further relates to an arrangement provided with a hoisting member (1) for hoisting and, respectively, lowering a floatable device (8). The arrangement comprises floating means (11) which float as such and act on a point (10) at the hoisting members (1), as well as flexible interconnecting members (1c) for engagement between said point (10) and said floatable device (8).

Description

A FLOATING ARRANGEMENT AND METHODS RELATED THERETO

The present invention relates to arrangements and methods at devices capable of floating, such as rescue craft or the like, wherein the device is hoisted and/or lowered by means of a flexible primary hoisting member which in operation extends essentially vertically and which is included in a hoisting arrangement comprising hoisting means, e.g., a winch or the like device which is provided at a ship or at a corresponding arrangement. Especially, the present invention relates to a method for attaching to and, respectively, releasing from a flexible primary hoisting member, a device which is capable of floating on a water surface, e.g., a vessel such as a rescue craft or the like, suitably so that an attaching and, respectively, a detaching include coupling operations between the device capable of floating and a secondary hoisting member. The invention also relates to a method for connecting, in a releasable manner, a device capable of floating, wherein said device is hoisted and/or lowered by means of a flexible primary hoisting member which in operation extends essentially vertically and which is included in a hoisting arrangement which is provided at a ship or the like. The invention further relates to an arrangement for hoisting and, respectively, lowering a floatable arrangement in relation to a water surface, suitably for launching and, respectively, taking aboard rescue craft or the like at ships, the arrangement comprising at least one flexible primary hoisting member, known per se, which is provided at a hoisting arrangement.

Prior art includes various arrangements for launching, at a ship's side, floatable devices such as rescue craft, rafts and similar small craft. Often the purpose of these arrangements is to secure, in an emergency situation, a safe transfer of passengers and crew between the ship and the small craft.

One such known arrangement comprises davits, of which an outer end can be positioned out over the ship's side so that a hoisting member running form the davit can be attached to or separately be detached from the small craft when it is located on the water surface at the ship's side. Classic lifeboat arrangements at least comprise the feature that a lifeboat located on board the ship can be launched m this manner, the arrangement comprising engaging means which primarily are intended to be released from the lifeboat, which should be possible even m difficult circumstances with wind and heavy sea. In order to reduce the risks related to launching m rough sea a multitude of different arrangements have been developed, of which arrangements Norwegian Patent No. 89234 and British patent application No. 2 092 101 may serve as examples. In accordance with current regulations such hoisting devices usually are provided with self-tensionmg means m order to facilitate the coupling between a lifeboat and a hoisting cable, the purpose of such arrangements being an automatic compensation of the impact of heavy sea. Again, an example of such devices can be seen, ι.a., m O-publication No. 81/01402.

Nowadays an ever growing importance is attached to enabling ships, when needed, also to rescue people m distress, and then the situation arises, where said hoisting member, usually a hoisting cable or the like, m a safe manner also ought to be attachable to a small craft which is floating freely alongside the ship. Various technical solutions have been developed for this purpose, which, however, often are more or less complicated and cumbersome m use and the operation of which often being unreliable m rough weather.

Examples of such arrangements are disclosed, e.g , m W0- publication No. 89/09723, m Norwegian publication No. 141929 and m Swedish patent No. 505 365, wherein a lifeboat or the like can be run into a cradle-like device which as such itself can be hoisted so that said cradle at the same time lifts the lifeboat from underneath. The general structure of all of these devices is heavy and complicated, and they are unreliable in operation. They cannot either, as such, be used in connection with the davits, known per se, which for the launching of lifeboats can be found on most ships .

Attempts have also been made to solve the problem in a manner which is disclosed in British patent application No. 2 150 903, by providing a device which is floating as such and wherein a jaw clutch coupling directly attaches to attachment means provided at the lifeboat. This construction requires an absolutely exact fit between the lifeboat and the jaw clutch coupling, which in practice is very hard to achieve in heavy sea .

The object of the present invention is to provide a simple way for attaching lifeboats, rescue craft or similar freely floating arrangements to a hoisting member, also in conditions where the connection of the hoisting member to the small craft can be done even by hand.

A further object of the present invention is to provide an arrangement where at a ship already existing davits, lifeboats and the like to a wide extent can be utilized without difficulty and extensive modifications.

The problems presented above and the objectives set up for their solution are solved by the present invention in accordance with the appended claims. Thus, in accordance with the present invention, the method related to attaching floating devices is characterized in rendering a point at said primary hoisting member, by means of separate floating means, into such a position in relation to the floatable device that a connecting secondary hoisting member acting between said device and said point, while a slack is preserved, can be connected for a hoisting action or, respectively, be released from such a connection. Further, in accordance with the present invention the method for connecting a device capable of floating is characterized in that said device capable of floating and separately provided floating means are maintained in a mutually generally horizontally centered position in such a way that one or several first connecting points at said device will be located essentially underneath and at a distance from one or more co-operating second connecting points at said floating means, said distance being maintained by means of said separately provided floating means through affecting primary hoisting members in such a manner that secondary hoisting members acting between said first and said second attachment points can be connected to or, respectively, released from said cooperation while maintaining a slack which is suitable for the coupling operation.

Again, the arrangement according to the present invention is characterized in that the arrangement includes, on one hand, floating means which are floating as such and acting at such a point at the flexible primary hoisting member which point is located at a vertical distance from the floatable device's engaging means, and, on the other hand, includes connecting secondary hoisting members which are flexible in at least one direction and arranged for connection between said point and said floatable device's said engaging means.

In general, the arrangement according to the present invention can be described so that a craft or a similar floatable arrangement is being handled freely hanging in a primary hoisting member via a secondary portion of the same arranged in line with said first portion, or via a correspondingly provided separate secondary hoisting member, while a docking unit is arranged, in order to position said secondary portion or hoisting member in relation to the water surface, to be hanging in another portion of the same hoisting member at a point which is located above said secondary portion. During handling in a vertical direction both the craft and the docking unit load the hoisting member essentially directly, while the water lifts the craft somewhat in relation to the docking unit and thus creates a slack in said secondary portion. When both said craft and said unit are located on the water surface said secondary portion has such a slack which renders possible a manual coupling operation between said portion and said craft .

Thus, the lifting force which the water exerts on a floating means which at least in a vertical direction is independent in relation to said craft and which is attached to said primary hoisting member, is utilized for vertically positioning a portion of said hoisting members in relation to said craft, suitably so that the buoyancy of said floating means is caused to act on said hoisting member at such a point which is located above said secondary portion or above such an end thereof which is intended to be coupled to said craft.

At any moment of coupling will one portion of said secondary flexible hoisting then be functionally located suitably at least slightly beneath engaging means arranged at the craft, or beneath an attachment point which is defined in some other way, to which point said portion will be connected, said portion meanwhile being horizontally essentially freely movable in relation to the attachment point. The craft can now be attached to or, respectively, released from this portion by means of, for example, a crane hook or a corresponding engaging means. In the position at the time of connection both the craft and the floating means will be located freely floating on the water surface. Since the vertical distance between said point provided at the hoisting member and said engaging means then is shorter than the vertical distance between said point and that portion of the hoisting member which is intended for coupling, said secondary hoisting member, in practice, will exhibit a slack which renders possible a performing without any risk of accidents the coupling operations, i.e. a releasing and, respectively, an attaching .

The present invention will now be described by way of example with reference to a preferred embodiment and the accompanying drawings, wherein

Figure 1 m cross section discloses an explanatory sketch of an arrangement m accordance with the present invention,

Figure 2 m a view seen towards a ship's side or the like discloses a practical embodiment of the present invention,

Figure 3 discloses the embodiment according to Fig. 2 viewed along the ship's side,

Figure 4 discloses a plane view of the same embodiment, and

Figures 5 to 8 disclose, step by step m detail and partially m cross section, how an attachment of the small craft to the hoisting member is performed by means of the arrangement according to Fig 1

According to Fig 1, an arrangement m accordance with the present invention comprises a flexible primary hoisting member 1, known per se, for example a hoisting cable or the like, which member at its upper end is attached to a hoisting arrangement including, for example, a winch 2 or some similar means which is shown m more detail m Fig. 2, by means of which means the vertical position of a lower portion la of said primary hoisting member 1 can be adjusted As Figs. 2 to 4 disclose m more detail, said hoisting member 1 is suitably guided over a davit 3 or the like means having an arm 4 which defines a horizontal position for an upper portion lb of said hoisting member 1 m relation to a device which is relatively stationary m comparison with the device capable of floating As in the embodiment disclosed herein said relatively stationary device can comprise a ship's side 5 or the like, or, e.g., an oil rig, a wall of a quay, or some other such major device, while the floatable device can comprise, e.g., a small craft or the like.

Thus, a ship's side 5 is roughly indicated in phantom in Fig. 1 in a schematic manner, and in the same schematic manner is shown a level 6 which, for example, indicates the height of a ship's deck or the like which is located at a considerable distance "a" from a water surface 7. This distance can, in practice, be anything from a few meters to tens of meters. In practice, since the water surface 7 heaves in pace with the waves, especially in rough weather, the distance between said level 6 and the water surface 7 may greatly vary in a relatively short period of time, which is illustrated in Fig. 1 by indications 7' and 7", respectively. A small craft 8 or some other floatable device which floats relatively freely on the water surface 7 behaves in the same manner. Therefore, in rough conditions it is often very difficult, and sometimes even impossible, to achieve in practice and without risk of injury a coupling between the small craft 8 and said lower end la of the hoisting member 1. In this connection, on the other hand, the vertical position of said lower end can be considered as relatively stationary in relation to said level 6. Of course, a ship in the water is not, in practice, fully stationary either, since also the ship 5 heaves. This heaving also causes the ship's deck to move horizontally, so that not either the horizontal position of the upper end lb of the hoisting member 1 will be in any way fully fixed. However, since the ship's movements are of a considerably slower character in comparison to the movements of the smaller craft, one can, in theory, primarily start from the assumption that said one end lb is essentially fixed while the other one is movable at least in vertical direction.

Likewise, for the sake of simplicity one can, in this con- nection, disregard the direct possibilities of vertically controlling said member 1 by means of the winch 2, since such controlling would require a very complicated functional connection to the constantly and essentially randomly varying difference in height "a" between, for example, said deck 6 and the water surface 7. In practice, of course, such a control possibility is of crucial importance for the actual hoisting, but for the actual coupling between the hoisting member and the craft the movements of said hoisting member 1 are too slow and inexact. At this stage, the problem can be concretely described as the question of connecting a generally stationary member 1 to a generally non-stationary body 8, and this problem has, in practice, been troubling sailors since the creation of ships with lifeboats. The question has been particularly important in harsh conditions and heavy weather, when at the same time also the amplitude of the movements as such is high.

According to the present invention the impact of the wave motion on the water surface 7 is now transferred to the lower portion la of the hoisting member 1 by allowing the buoyancy of means 9 which float on the water surface 7 to act suitably directly on an attachment point 10 which is connected to said lower portion la of the hoisting member 1. In practice, this is suitably accomplished by means of a framework 18 which is provided at a pontoon means, a buoy means or the like, which framework is included as a part of a floating arrangement 11 in order to position said attachment point 10. In Figure 1, a dash-dotted line is used to indicate an alternative position 7' for the water surface 7 and said framework 18. In this position 7' the distance between the level of the ship's deck 6 and said lower end la of the hoisting member is shorter than in the position indicated by the solid line, which in practice causes a corresponding slack in the hoisting member 1. Again, in another alternative position 7" (indicated by a dash line) , said distance is longer than in said position indicated by the solid line, which situation again requires the winch to give out of said hoisting member 1. The handling of these variations in the actual length of the hoisting member 1 will further be described later on. However, as is evident in the Figure, a distance "c" between said attachment point 10 and the actual water surface 7 will remain comparatively constant regardless of how the wave movement takes place, since the floating arrangement 11 is comparatively light and thus floats on top of the waves. Thus, this arrangement provides a functional connection or positioning between said lower portion la of said hoisting member 1 and the water surface 7. At the same time this, however, means that a functional positioning of said lower end la is achieved also in relation to all other such means which float on the water surface 7 at essentially the same spot and which have an essentially similar displacement and pattern of motion as said pontoons 9. In practice, rather extensive variations can here be permitted so that, for example, said floatable device can have a displacement of, for instance, 1.6 tons while its docking unit, i.e. the floating arrangement which performs the positioning of the primary hoisting members 1 can have a displacement of 0.6 tons, whereby the whole arrangement can be hoisted, with a good safety margin, in a normal 3 ton davit.

Thus, since the lower end la of said hoisting member 1, as discussed above, within very limited possibilities of relative movement, is positioned in accordance with the present invention to be located, all the time and essentially regardless of the sea heaving, in a clearly definable position in relation to the small craft 8 there will be no difficulty in making the connection, in a manner known per se , between the hoisting member 1 and the craft 8. Figure 1 discloses this in a general manner by means of a separate length of wire or the like coupling portion lc, which is shown to have a slightly exaggerated slack in relation to reality. Within the scope of this slack the task of coupling is easily done, for which the Figure very schematically shows co-operating engaging means comprising a hook 12, 12a arranged at at least one end of the secondary hoisting member lc, as well as a ring 13 which cooperates with said hook.

Even though the Figures disclose just one single secondary hoisting member lc having one respective first engaging means 12 which co-operates with a respective second engaging means 13, the number of secondary hoisting members lc acting in parallel and, respectively, the number of co-operating first and second engaging means 12, 12a and 13, 13a, respectively, can in some embodiments be more than one. Suitably, said cooperating engaging means 12, 13 can, in practice, be of different designs, but this practical design has no major importance for the inventive idea as such. The problem is not actually related to the coupling as such, but rather to the question of managing, on one hand, the free mutual movements of the members and, on the other hand, the obvious risk of accidents caused by attempts to attach, in spite of such movements, a relatively light moving craft 8 to a hoisting member 1, where said craft in any case still has a not unessential mass and moment of inertia of its own, while said hoisting member is essentially immobile in relation to the craft 8. In Figure 1 the coupling portion lc is disclosed, in order to show the principle, as a flexible loose member having cooperating engaging means 12, 12a and 13, 13a, respectively, at each end, but in practice the most favorable arrangement is one where one end is more or less permanently attached, suitably so that the upper end 12a is attached at least in advance to the engaging means 13a of said the floating arrangement 11, if it is not attached thereto in a completely fixed manner. In Figure 1 engaging means comprising an open hook and a simple ring have been schematically shown, but in practice these means are designed, of course, to match all such safety precautions which are required for hoisting, for example, rescue crafts 8 including crew and people in distress. Figures 5 to 8 show in more detail embodiments wherein the actual rescue craft 8 is provided with heavier hook means 13, for instance known remotely releasable means, while the associated engaging means 12 are essentially light weight means, which facilitates their handling and minimizes the risks in heaving sea.

Thanks to the slack in the secondary hoisting member lc the co-operating engaging means 12, 13 can be attached with no lifting effect whatsoever during the actual coupling operation, and with this the risk of such injury to people or equipment is eliminated which possibly arises at coupling. When said means 12 and 13 have been interconnected the craft and the pontoon means 9 can continue to float freely, but, contrary to the earlier stage, the whole arrangement can now also be hoisted as an entity, which situation will be described below in more detail .

Figures 2 to 4 generally present a favorable arrangement for putting in practice the present invention. This arrangement includes a pulling means 14, for instance a drag wire which extends in a generally slanting horizontal manner in the direction of the ship's side 5. Suitably, this pulling means 14 emerges from a favorably collapsible boom 15 which comprises winching means 16 for controlling the length of the drag wire 14, where said winching means suitably comprise shock absorbing means for counteracting any jerks. By means of said drag wire 14 the general direction is stabilized for the floatable docking unit 11 which is constituted by the generally parallel pontoons 9, which stabilization makes it easy to drive the craft 8 in between the pontoons 9 also in rough weather and heavy sea. The entity comprising the craft 8, the pontoons 9 and the framework 18 arranged in connection with the is also stabilized by means of said pulling means 14 when said entity is hoisted and, respectively, lowered. The length of the drag wire 14 and the general geometry of the arrangement is preferably adapted to the dimensions of the ship so that the length of the pulling cable during launching will be adapted to the point where the docking unit 11 and the rescue craft 8 meet the water surface . In order to ensure a steering capability it is appropriate that the drag wire's 14 elevation angle from the water surface 7 up towards the deck should not exceed about 33°.

The embodiment disclosed in Figs. 2 to 4 favorably includes the ship's standard cranes or davits 3, which already, according to current requirements, are provided with a self tensioning feature. This feature, which usually can be switched on and off, normally works for such loads as lifeboats and the like, which loads have a weight exceeding 300 kilograms, and it ensures that the hoisting cable 1 automatically will be tensioned so that slack is prevented when the waves lift the lifeboat, while it gives out more of the hoisting cable as the waves subside. At the present invention, this self tensioning device operates based on the dead weight of the docking unit 11 which is constituted by the pontoon arrangement. For conventional fast rescue craft 8 said dead weight suitably is in the order of 600 kilograms. By means of this device there is no difficulties in maintaining the position shown in Fig.l, i.e. a position where the hoisting member 1 is kept generally under tension to a correct length above the attachment point 10, while such a self tensioning feature, as indicated above, renders a direct engaging of the hoisting member 1 to the rescue craft 8 difficult and in many cases outright dangerous, which is why this feature in conventional lifeboat arrangements normally require manual control .

Fig. 3 shows that the docking unit 11 which is constituted by said pontoon arrangement 9 and said framework 18 suitably is designed as a catamaran-like device, wherein the pontoons 9 at the same time constitute fender means against the ship's side 5. As described in more detail below, the rescue craft 8 or the like will at a hoisting operation be directly suspended from the hoisting member 1, the docking unit 11 thus carrying only its own weight. Thus, the actual docking unit 11 can be made very light. In the embodiment shown, the docking unit 11 comprises a generally U-shaped cradle which favorably is open at the stern, which cradle is formed of said suitably pontoonlike buoyant bodies 9. Said buoyant bodies 9 are connected by means of said framework 18, which above an open space forms a hoisting yoke by means of which the docking unit 11 can be hoisted. At the same time, said hoisting yoke serves as a hoisting means for the attachment point 10 at the hoisting members 1. Thus, while the docking unit 11 is floating said attachment point 10 will be positioned, at all times and regardless of the effect of the heave of the sea, at an essentially conctant distance "c" from the water surface 7.

The open space formed between the pontoons 9 is intended to receive the rescue craft 8, and favorably it is dimensioned accordingly. Fig. 3 further shows that the framework 18 favorably also comprises one or more connecting supports 19 which extend below said open space and thus reinforce the structure. This support 19 is arranged at such a distance "b" from the bottom of the rescue craft 8 that the weight of the craft to no essential extent will be resting on the support 19 even in a hoisted position. Thus, during a hoisting the rescue craft 8 and the docking unit 11 will be freely suspended at the primary hoisting member 1 as well as, respectively, at the secondary hoisting member lc attached to it, essentially independent of each other, while a clearance "b'" is maintained, i.e. the distance "b" reduced by the slack in the secondary hoisting member lc . Thus, the whole framework 18 can be designed to have very light structures, since they mainly need to support just their own weight. Thus, the docking unit 11 can be composed of, for example, foam- filled plastic tubes which serve as said buoyant bodies 9, while the framework 18 suitably can be made of aluminium, fibre glass, plastics, steel or the like.

The use of the arrangement according to the present invention will now be described in more detail with reference especially to Figures 5 to 8, which show how docking and hoisting of a rescue craft 8 is performed with the aid of a docking unit according to the present invention. It should be noted that the launching is performed in accordance with the same general principles but in reverse order. In general terms, the launching function can thus be described as follows:

A craft 8 is suitably parked on the deck 6 at the ship's side 5. Using the ship's standard hoisting device 2, 3 the craft 8 and the docking unit 11 are lowered into the water. Here the docking unit is preferably connected by means of a drag wire 14 fore to the ship in order to give the docking unit 11, and thus also the craft 8 connected to it, a forward speed. When the docking unit and the craft are in the water engaging means 12, 13 at the attachment portion lc are released and the craft 8 floats out of the docking unit 11 while maintaining the forward movement .

The retrieving on board is done in a corresponding manner so that the craft 8 runs in into the docking unit 11, whereafter the crew engages a short length of wire lc to means 13 provided at the craft 8 for this purpose. Here, a preventer wire 17 serves as a lock between the craft 8 and the docking unit 11 for preventing such horizontal movements, which otherwise could be possible within the range of the slack in the length of wire lc. The distance "b" between the keel of the craft and a bottom rail 19 which preferably is arranged for stabilizing the floating means, i.e. the docking unit 11, is larger than the slack in the short length of wire lc . When the craft 8 has been attached in this way the actual hoisting is performed at the primary hoisting member 1, whereby at first the docking unit 11 will be hoisted up somewhat while the craft 8 still floats on the water surface 7. As the short length of wire is stretched and the slack is used up, the primary hoisting member 1 starts hoisting the actual craft 8 as well. In this manner one avoids having the craft 8 resting on top of the docking unit 11, which thus need not be dimensioned for carrying the weight of the craft. In spite of that, at the same time an arrangement has been achieved, where the cooperating engaging means 12, 13 will move at essentially the same pace and thus they can easily be attached and, respectively, released.

In particular, the course of events will now be described in more detail with reference to a rescue craft 8 known per se . Thus, in accordance with Fig. 5 the retrieving on board of the rescue craft 8 is commenced at a starting position where the docking unit 11 floats essentially freely on the water surface 7. At this stage, a primary hoisting cable 1 is attached to, for example, a davit 3 which is suitably arranged in a pivotable manner on the deck of the ship (not shown in Figs. 5 to 8) , while a winch arrangement 2 connected to said davit 3 comprises means which, suitably with a self tensioning action, tighten the hoisting cable into a position shown in Fig. 5. The ship is moving forward at a speed of suitably 5 to 8 knots, while a drag wire 14 provided at a suitably collapsible hauling boom 15 tows the docking unit 11 as described above. Through the effect of said drag wire 14 the docking unit 11 is kept at a safe distance "e" from the ship's side 5, the position at the same time being such, that the hoisting cable 1 extends essentially vertically. This position also corresponds to the situation where the docking unit 11 together with the rescue craft 8 is being launched off the deck.

At this stage the craft 8 can move essentially freely at its own power into the space between the pontoons 9 of the docking unit 11 and, respectively, out of this space. As shown in Fig. 5, the coupling portion, i.e. the secondary hoisting member lc, can be constituted by a portion of said hoisting member 1 or, alternatively, be a separate corresponding device provided at the hoisting yoke of the framework 18, for instance the separate length of wire lc described above, which separate length of wire is essentially loosely arranged as a suitably direct extension of the hoisting member 1. This portion lc comprises a crane hook 12, a loop or the like means for co- operation with corresponding means 13 arranged at the rescue craft 8, and said portion preferably exhibits a slack of about 100 millimeters. As the Figure shows, a preventer wire 17 is preferably arranged for stabilizing the movements of the length of wire lc and thus for facilitating the engagement operations . Said preventer wire 17 also prevents the rescue craft 8 from sliding out of the docking unit 11 at hoisting.

Fig. 6 shows that the helmsman at the rescue craft 8 preferably keeps the bow against the docking unit 11 by maintaining a certain forward thrust in order to, at the same time, in this manner clearly position the engaging means 13 provided at the craft in relation to the docking unit 11 and thus also to the engaging means 12 of the secondary hoisting wire lc . The docking unit is preferably designed so that it, as such, guides the positioning. It is to be noted that the rescue craft 8 as such is not in engaging contact with the docking unit's rail 19 located underneath nor with any other submerged portion of the docking unit 11, but on the contrary so that there is a certain vertical clearance "b" between boat and dock. Even in a rough sea the docking unit 11 follows the motions of the rescue craft 8 in the water in such a way that entering and, respectively, exiting as well as the engagement operation between craft and unit can proceed without difficulty.

Since both the craft 8 and the docking unit 11 will have essentially the same pattern of motion in the water a distance "d" between said point 10 and said engaging means 13 will remain essentially constant regardless of the heave of the sea. Due to the slack in the lower portion lc of the secondary hoisting members, a coupling maneuver between the engaging portion 12 of the hoisting member and the engaging means 13 of the rescue craft can be performed at this stage, for example, manually without risk of accidents or injuries, while the self tensioning of the davit arrangement as such reacts to the weight of the docking unit 11 and keeps the hoisting cable 1 stretched. In this manner any swinging motion of the hoisting cable 1 has been completely eliminated, which motion, at a rolling ship in rough sea and hoisting heights of even 30 meters or more, otherwise totally would render impossible an engagement between craft and docking unit . The engaging means 12, 13 as such are suitably known per se, favorably so that they are manually releasable co-operating means, one 12 of which is provided at the free extension of the hoisting member 1, and a second one at the rescue craft so that at hoisting the connection 12-13 as such can carry the full load constituted by the craft.

At hoisting, which as such is shown in Fig. 8, the self tensioning feature of the hoisting winch is deactivated. At this stage the docking unit 11 gets lifted first, since it is directly attached to the hoisting cable 1 via the attachment point 10 and the hoisting yoke 18. Meanwhile, the slack in the functionally lowest portion lc of the hoisting cable 1 is stretched, after which the hoisting cable acts directly also on the rescue craft 8, the bottom of which still remaining clear of the bottom rail 19 by said clearance "b'" and thus the bottom will be to no essential extent supported by the docking unit. In this way mutually interconnected the whole arrangement can be handled as an entity, but at the same time it can be handled as individual mutually independent parts 8, 11 carried by the hoisting cable 1, while the pontoon 9 of the docking unit 11 at the same time preferably serves as a fender against the ship's side 5.

As such, the specific design and location of the engaging means are irrelevant for the arrangement's function. Thus, any one of the co-operating engaging means can be included as part of the craft, while another part can constitute a structural part of the coupling portion of the hoisting members. It is also irrelevant for the function how, for example, hook means and loop means, respectively, in practice are designed or located. Above a favorable embodiment has also been described mainly as an example, wherein a coupling portion having a slack, for instance a length of wire, is attached more or less permanently at the floating means, i.e. at the docking unit 11. It is obvious for a person skilled in the art that the same function can be achieved also at a reverse arrangement wherein the coupling portion primarily is attached to the craft 8, while the docking unit 11 comprises engaging means, to which the coupling portion will be attached. It is also obvious that instead of a length of wire or some similar coupling portion which is flexible in all directions, also means having a more rigid nature, for example restrictedly telescopic and favorably laterally movable means can be used. According to one embodiment the secondary hoisting member lc comprises longitudinally elastic means in order, for example, to facilitate the engagement.

Above the present invention has been described in connection with floatable devices such as self propelled small craft of the lifeboat category or the like, but to the person skilled in the art it is clear that the present invention also can be applied to other floating objects, for example bundles of logs or other objects which rather have the character of cargo.

Some preferable embodiments of the present invention have been described above, but to a person skilled in the art it is also clear that the present invention also can be applied in many other ways and in other embodiments within the scope defined in the accompanying claims.

Claims

1. A method for attaching and, respectively, releasing a device (8) which is capable of floating on a water surface (7, 7', 7"), for example a minor vessel such as a rescue craft or the like, to or, respectively, from a flexible primary hoisting member (1) which is maneuvered by means of hoisting means (2) arranged, for example, in a hoisting arrangement (3) at a ship or the like, c h a r a c t e r i z e d in that a point (10) at said primary hoisting member (1) is brought by means of separate floating means (11) into such a position in relation to said floatable device (8) that interconnecting secondary hoisting member (s) (lc) acting between said device (8) and said point (10) can be connected, with a slack, for commencing a hoisting action, or, respectively, can be released from such a connection.

2. A method according to claim 1, c h a r a c t e r i z e d in maintaining said slack under such circumstances when both said floating means (11) and said device (8) capable of floating are floating freely on the water surface (7, 7', 7") in a mutual disposition which is generally horizontally centered, while allowing a hoisting impact from said primary hoisting member (1) to act, during hoisting, on one hand essentially directly on said floating means (11) and, on the other hand, to act via an extension constituted by said interconnecting secondary hoisting member (s) (lc) essentially directly also on said device (8) capable of floating.

3. A method according to claim 1 or 2, c h a r a c t e r i z e d in maintaining said primary hoisting member (1) , by means of said hoisting means, in a generally stretched state, suitably by means of self tensioning means provided at said hoisting means, so that said point (10) will be positioned, in a manner which is essentially independent with respect to any level variations (7', 7") of the water surface (7), at a principally constant distance (c) from the water surface (7), said distance being defined by said floating means (11) .

4. A method according to any one of claims 1 to 3 , c h a r a c t e r i z e d in that the horizontal position and suitably also the orientation of said floating means (11) is defined, by means of separate pulling members (14) which suitably are connected to the ship or the like via a boom member (15) , so that said device (8) capable of floating as well as said floating means (11) easily can be mutually centered horizontally.

5. A method according to any one of claims 1 to 4, c h a r a c t e r i z e d in that said interconnecting secondary hoisting member (s) (lc) is (are) constituted by a device which is attached essentially permanently to said floating means and/or to said primary hoisting member (1) , said device suitably being a length of wire or the like, a distal engaging portion (12) of which favorably being stabilized by means of preventer means (17) connected to a point located horizontally at a distance from said point .

6. A method for engaging, in a releasable manner, a device (8) capable of floating, such as a rescue craft or the like, to a flexible primary hoisting member (1) which in operation extends essentially vertically and which is included in a hoisting arrangement (3) provided for hoisting and, respectively, lowering at a ship or the like, c h a r a c t e - r i z e d in that said device (8) capable of floating as well as separately arranged floating means (11) are maintained in a mutually generally horizontally centered disposition so that one or several first attachment point (s) (13) at said device will be positioned essentially underneath one or several second attachment point (s) (10, 12) at at distance (d) therefrom, said second attachment point (s) being located at said floating means (11) and co-operating with said first attachment points, wherein said distance (d) is maintained by means of said separately arranged floating means (11) via an influence on said primary hoisting member (1) in such a manner that secondary hoisting member (s) (lc) acting between said first and said second attachment points (13, 12, 10) can be attached for as well as, respectively, released from action under a slack which is suitable for the engaging function.

7 . A method according to claim 6 , c h a r a c t e r i z e d in that said device (8) capable of floating is brought to be at least .partially surrounded by separate floating means (9, 11) in order to implement a horizontal centering, a vertical clearance (d) is maintained between said device (8) capable of floating and said floating means (11) for the time they are both floating freely on a water surface (7, 7', 7") , a connection (12-13) between said secondary hoisting member (s) (lc) and at least one of said attachment points (13, 12, 10) is established or, respectively, released while said device (8) and said floating means (11) both are floating essentially freely on the water surface (7, 7', 7"), while allowing, during a hoisting or lowering phase, at least a major part of the weight of said device (8) capable of floating to directly act on said flexible primary hoisting member (1) , suitably conveyed via said secondary hoisting member (s) (lc) .

8. An arrangement for hoisting and, respectively, lowering in relation to a water surface (7, 7', 7") a device (8) capable of floating, suitably for launching and, respectively, taking aboard rescue craft or the like at a ship, said arrangement comprising at least one flexible primary hoisting member (1) provided at a hoisting arrangement (2, 3) , as known per se, c h a r a c t e r i z e d in that the arrangement, on one hand, comprises floating means (11) which float as such and act at such a point (10) at said flexible primary hoisting member (s) (1) which point is located at a vertical distance (c) from en- gaging means (13) on said device (8) capable of floating, and, on the other hand, interconnecting secondary hoisting member (s) (lc) which is (are) flexible in at least one direction, said secondary hoisting member (s) being arranged to be attached between said point (10) and said engaging means (13) on said device (8) capable of floating.

9. An arrangement according to claim 8, c h a r a c t e r i z e d in that said secondary hoisting member (s) (lc) is (are) constituted by member (s) which is (are) flexible in at least one direction, which member (s) extend (s) as far as, or preferably generally further than, a distance (d) between respective attachment points (13, 10) which are provided, on one hand, at said device (8) capable of floating and, on the other hand, at said floating means (11) in such a way that said secondary hoisting member (s) (lc) exhibit (s) a slack when the floating device (8) as well as said floating means (11) both are floating on the water surface (7, 7', 7") due to their inherent buoyancies .

10. An arrangement according to claim 8 or 9, c h a r a c t e - r i z e d in that in that said floating means (11) includes a framework (18) having pontoons (9) or the like, which frame^¬ work to suitable extent extends above and around a space for receiving said device (8) capable of floating, favorably so that an upper portion of said framework (18) comprises means for a suitably lockable connection to an attachment point (10) at said primary hoisting member (s) (1), which point is ar^¬ ranged at said portion.

11. An arrangement according to any one of claims 8 to 10, c h a r a c t e r i z e d in that said secondary hoisting member (s) (lc) include (s) a length of wire provided at said framework (18) , which length of wire is longer than said distance (d) to engaging means (13) provided at the floating device (8) when said device is floating on the water surface (7, 7', 7"), and suitably so that said floating device (8) during hoisting will be essentially completely carried by said length of wire (lc) without supporting contact to said floating means.

12. An arrangement according to any one of claims 8 to 11, c h a r a c t e r i z e d in that the arrangement further comprises a hauling device (14) , suitably a drag wire or the like favorably flexible device, by means of which said floating means (11) can be guided to a desired horizontal position and preferably also to a desired orientation, suitably so that boom means (15) are provided at the ship for steering of that end of said hauling device (14) which connects to the ship.

13. An arrangement according to any one of claims 8 to 12, c h a r a c t e r i z e d in that said flexible primary hoisting member (s) (1) and/or said hauling device (14) comprise tensioning, attenuating or the like means, suitably so that the general position of said primary hoisting member (s) is defined by said means, whereas the position of an engaging portion (12) of said secondary hoisting member (s) (lc) in relation to said floatable device's (8) engaging means (13) which co-operate with said portion is defined by the buoyancy of said floating means (11) , preferably so that the engaging portion (13) will be located without power impact in such an immediate proximity to the engaging means (12) that a connection can be essentially implemented even manually.

14. An arrangement according to any one of claims 8 to 13 , c h a r a c t e r i z e d in that said engaging portion (12) at said secondary hoisting member (s) (lc) , or a portion located close to said portion, by means of a preventer wire (17) or the like is connected to said framework (18) in order to limit the free movement of said engaging portion (12) and particularly that of the engaging means .