IE42044B1 - Apparatus for capturing a floating object - Google Patents

Abstract

1469373 Vessel for retrieving floating objects J RAY McDERMOTT & CO Inc 25 June 1975 [16 Aug 1974] 26953/75 Heading B7A Apparatus for capturing a floating object, for example, an anchor buoy, comprises a catamaran vessel 11 and a retrieval structure between the hulls which can gather and hold the object whilst the vessel is underway, and can be moved vertically to raise the object above the water. The structure 15 is formed by two guide bars 23 connected to a cradle 19 and pivoted to a vertical movable support (35), Fig. 5, not shown. The cradle is connected to a hoist 61 by a cable (43). A crane 53 is available for lifting the buoy out of the cradle. A pilot house 21 is disposed forward of the craft. Bow thrusters 65, 67 assist the manouvering of the the vessel. A guard (64), Fig. 3, not shown, is disposed around the propeller. The cradle 19 can be mounted in tracks on the inboard sides of the hulls, and can be raised by hydraulic cylinders. The guide bars can extend forward to the bows. The pilot house can be disposed aft of the retrieval structure. [GB1469373A]

Description

42044 The present invention relates to an apparatus used in the at-sea retrieval of floating· objects such as anchor buoys and seismic buoys. The apparatus of this invention may be used for the purpose of picking up any floating 5 object at sea, such as a buoy, in order to retrieve or reposition a subsea article such as an anchor attached to the buoy, or more simply to retrieve and collect free floating objects.

Anchor buoys are employed, for example, to mark the anchors of a pipelaying barge which utilizes the anchors to position' itself and maintain itself on course, for example, during a pipelaying operation. As the barge lays pipe it becomes periodically necessary to reposition the anchors of the lay barge. This is accomplished by picking up the 15 anchors via cables or other pendent lines attached to the and anchors / running through buoys floating on the surface.

Pneumatic buoys having central hawsepipes through which the cables or pendent, lines pass are commonly used. The anchors are then repositioned with the buoys again marking the new 20 position s. of the anchors. .

In an at-sea pick-up operation of any floating object, the task becomes'progressively more difficult as sea conditions worsen. The pick-up is potentially hazardous where personnel are required to be near the rail of an ocean-going 25 vessel while assisting in the retrieval operation. One method to retrieve buoys involves use of an over-the-side capture apparatus utilizing a boom and/or winch to capture the buoy and reposition the anchor. Such an arrangement presents difficulty in maneuvering the vessel into position. 2 4 3 0 4 4 .Since steerage is particularly difficult in high sea, the efficiency of such an apparatus is markedly reduced when most needed. There is an additional disadvantage to this method caused by the parallax effect of the retrieval apparatus being offset from the centreline of the 5 vessel. Thus the exact placement of the retrieval apparatus is render ed more difficult by having to visually ascertain the track of the vessel and the offset track of such apparatus while allowing for wind and water action.

Another method used is simply for a crew member to physically place 10 a hook on the floating object and then to retrieve the object with a boom and or winch apparatus. This method necessarily involves increased difficulty for crew members and becomes increasingly hazardous and difficult with increasing wave intensity.

According to the invention there is provided an apparatus for 15 capturing a floating object which comprises a powered catamaran vessel having two spaced hulls, said vessel being suitable for manoeuvrable advancement through a body of water toward an object floating at the surface of the water,· and retrieval apparatus disposed between said hulls retrieval for capturing and holding the object within said/apparatus while said is 20 vessel/under way comprising a cradle that provides support to the underside of the object and unrestricted access to the object from above, and guide members which extend forwardly and outwardly of said cradle to direct the object away from said hulls and into said cradle, said ‘ retrieval apparatus being secured to the inboard surface of each said hull 26 at a position forward of said cradle and being movable in a vertical direction to a position below water level to permit capture of the is object while said vessel/under way and to a position completely above to the water level/ alternatively permit said object to be raised out of the water or permit said vessel to overrun the floating 30 object. 3 / 420 4 4 An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a perspective view of a catamaran tugboat, 5 with a portion thereof cut away to show the retrieval apparatus located in the approximate center of the vessel* Figure 2 is a frontal view of the catamarah tugboat and retrieval apparatus, showing bow thrusters on the frontal portion of each of the twin hulls.

Figure 3 is a side view of propeller guard apparatus.

Figure 4 is a top view of the retrieval apparatus.

Figure 5 is a side view of the retrieval apparatus in two positions with the shaded outline of a buoy or other lb retrieved object in its captured position and showing a detail of the structure mounting the retrieval apparatus to the inboard hull surface.

Figures 6A through 6D are schematic representations of the apparatus of. this embodiment illustrating a sequence 20 which may be used in retrieving an anchor buoy and repositioning an anchor.

Referring to Fig. 1, there is shown a vessel 10 which represents an embodiment of the invention." The vessel comprises catamaran hulls 11, deck 13, and associated 25 superstructure. ' 4 , I 43044 The retrieval apparatus is generally shown at 15. The guide retrieval apparatus comprises main support/bars 23, and the buoy retainer means or cradle 19 which catches and supports the buoy. The retrieval apparatus 15 is disposed, between 5 the catamaran hulls 11 and is affixed to the inboard surfaces 12 of the hulls so as to be generally symmetrically arranged about the centerline of the vessel as may be seen in Figure 2. The advantage of this feature becomes more readily 1 0 apparent when considering operation of the tugboat in rough ' seas or fading light. The pilot house 21 and a steerage control console (not shown) are located in proximity to said centerline. Thus, the alignment of the retrieval apparatus 15 along the path of approach to a floating object is greatly 15 facilitated by the fact that the apparatus is not offset from.the centerline of the path of travel of the vessel. It is only necessary for the operator of the tugboat to orient his path of travel directly toward the desired object, and said object will be properly situated in relation to the 20 retrieval apparatus so as to be guided into the proximity of said apparatus for capture.

As the vessel approaches a buoy and passes over it, the two support guide bars 23 which are angled toward the center-line of the vessel will generally tend to centralize the 25 buoy between the hulls and direct it toward cradle 19. It may be desirable, depending upon buoy design, to provide a number of support guide bars in an arrangement somewhat parallel to those shown at 23 to insure the buoy is directed to cradle 19. Cradle 19, as shown, is designed for catching 30 a spherical anchor buoy 47 of the type having a central cable which is connected to the subsea anchor. Typically 5 4ZU44 r 1 such buoys are pneumatic and are constructed of rubber or like flexible material. The anchor pendent line 30 passes centrally through the buoy and terminates atop the buoy in an eye 75 or similar fixture to which connection may be 5 readily made to retrieve the anchor 32. Art anchor cable 34 extends to the barge secured by the anchor. It will be appreciated that various configurations of cradle 19 could be adapted to retrieve different buoys of other shapes or types.

Referring to Pigs. 4 and 5, there is shown respectively a top View and a side view of the retrieval apparatus. Which could also be referred to as a buoy catcher, as well as means for positioning the retrieval apparatus relative to the waterline of the vessel. Pig. 5 is taken along section 15 line 5-5 of Pig. 4.

Support guide bars 23 angle inwardly from the inboard hull surfaces of the vessel, and are joined to form a generally ϋ-shaped structure. As shown, a rear support bar 25 connects the two support guide bars, lower cradle bars 26 and 27 are 20 suspended from the support guide bars and define a slot 29 which will accommodate a cable affixed to the buoy when the buoy is in position in the cradle. Upper retaining bars 31 are also supported from support guide bars 23 and provide a barrier or fence holding the buoy in the cradle while the 25 vessel is .under.way. Centering bars 33 perform the final directing function to insure that the buoy is directed properly into the cradle. As indicated above, support guide bars 23 function as the initial directing means for the buoy or other floating object to be retrieved. The more sharply 30 angled centering bars 33 perform the final function of centralizing the cable below the buoy in directing the buoy 6 i , I ' 42014 into the cradle formed by the upper retaining bars 31 and lower cradle bars‘26 and 27. Once in position, the buoy will rest in the cradle 19 and will be firmly maintained in position. Water moving relative to the buoy resulting from 5 vessel movement tends to force the buoy firmly against the rear portion of the cradle 19 and upper retaining bars 31. Accordingly, the upper retaining bars 31 should be sufficiently high that water movement will not propel the buoy up and out of the cradle once it has been positioned in the cradle.

It should be noted that the cradle contains no restriction to raising the buoy in a vertically upward direction. It will be apparent to those skilled in the art that cradle design and the elevation of the support guide bars relative to water level may depend upon the particular configuration of the buoys or other objects to be captured. The cradle should be so designed that the buoy will be firmly held in place without damage by the relative movement of water and yet can be easily and readily raised vertically from the cradle. As shown in Pig. 5 and dotted outline, a spherical 20 buoy is shown within the cradle with the upper retaining bars 31 restraining any rearward movement of the buoy nut of the cradle.

It should also be noted that the retrieval apparatus and cradle are preferably of an open truss network design.

Thus, for example, upper retaining bar 31 is supported by support members 28 in order that the entire retrieval apparatus presents minimum drag to the vessel when the vessel is under way.

The forward end of each of the support guide bars 23 terminates in a pivot block 35. Pivot block 35 is pivotally 30 mounted with respect to carriage member 37 Which in turn is disposed for vertical movement within track 39 . 7 *Λ«ΐ4 t » secured to the inboard hull surface 12. A hydraulic cylinder 41 is connected to carriage member 37 by a connecting rod 42. Accordingly, carriage member 37 can be positioned at any desired place along track 39. It will be appreciated that 5 other suitable means to position the forward ends of the support guide bats 23 at varying elevations with respect to the waterline of the vessel could also be used. For example, a cable and winch arrangement could be used in place of hydraulic cylinder 41. Alternatively, carriage member 37 1o might be connected to a vertically disposed screw, enabling vertical positioning of the carriage member by rotating the screw into a support member utilising a hydraulic motor or electric motor or the like. Likewise any suitable track arrangement which disposes a carriage member such as 37 for 16 vertical movement along an inboard surface of the opposing catamaran hulls may be used.

By activating hydraulic cylinder 41, the forward ends of support guide bars 23 can be positioned at any desired level relative to the waterline. Thus, when the vessel is not 20 being used for capture of floating Objects or buoys, the guide bars can be,positioned out of the water as shown in Figure 6A in order to minimize drag.· Similarly, depending upon buoy design or depending upon the wave action of the seas, the forward ends of the support guide bars 23 may be 25 positioned at-various heights relative to the waterline in order to assure that the guide bars function efficiently to direct the buoys toward the cradle 19.

The aft portion of the retrieval apparatus is connected by cable 43 to hoist 61, shown in Figure 4 on the port side of deck opening 49. A similar hoist may be located on the starboard side of opening 49. Opening 49 in deck 13 is 8 42044 directly above the cradle 19 of the buoy catcher to enable access to the buoy or other object within the cradle from deck 13. Hoist 61 enables the aft portion of the buoy catcher to be raised to the proximity of the deck, pivoting guide 5 the forward ends of support/bars 23 in pivot blocks 35.

Any suitable lifting mechanism may be used to perform the function of hoist 61. For example, hydraulic cylinders or a suitable winch and cable arrangement might be employed. Illustrated hoist 61 includes a hydraulic cylinder 63 having 10 movable head 64. The hydraulic cylinder and movable head mount two sets of sheaves 65 and 67 to form a drawworks around which cable 43 may be wound a suitable number of times to obtain a desired lifting advantage'. For example, if cable 43 is wound around the sheaves 65 and 67 six times, 15 one foot of travel of sheave 67 in the direction of the arrow will result in six feet of lift to the buoy catcher.

The cable then passes over .guide sheaves 70 and 72 to retrieval apparatus 15. Thus, the illustrated hoist provides a convenient mechanism to raise the buoy catcher a prescribed 20 amount so that the captured object will be at the desnred height in opening 49. Hoist 61 also thereby enables troper positioning of the cradle at a desired height relative to the waterline during buoy catching operations. It also enables the aft portion of the retrieval apparatus and the 25 cradle to be lifted clear of the water when buoy catching operations are not being conducted.

Thus, when buoy catching is not under way, each carriage member 37 is lifted high in track 39 and the drawworks of hoist 61 extended to position the retrieval apparatus entirely 30 out of the water as shown in Figure 6A. When carriage 1 42044 member 37 is lifted, rear support bar 25 is positioned in i rest 69 which supports the aft portion of the retrieval apparatus. Λ safety chain 71 may also be desirably provided. During buoy catching operations, the carriage members 37 5 would be first positioned at an efficient elevation to assure directing of the buoys to cradle 19. Hoist 61 would then be adjusted to provide an appropriate elevation to the rearward section of the retrieval apparatus and the cradle thus positioning the retrieval apparatus as shown in Figure 10 6B. When a buoy or other floating object has been overrun by the vessel and is firmly within the cradle, the hoist would be activated and the rearward portion of the retrieval apparatus could be elevated so that the upper portion of the buoy (shown at 47 in Fig. 1} would be proximate the deck 13 15 of the vessel. The opening 49 in the deck of the vessel approximately above the position of the buoy in the retrieval apparatus enables access to the buoy from the deck.

It is desirable for a suitable catwalk 73 (in Figure 5) to be positioned over the rear portion of Opening 49 in 20 order that a crewman might have ready access to the top of the buoy when in the elevated position.

After buoy 47 has been elevated into opening 49 in order to provide access to the buoy by a crewman, the eye 75 atop buoy pendent line 30 can be suitably secured to a cable 25 51 suspended from crane 53. The captured object may then be elevated onto the deck or alternatively the anchor pendent line 30 may be suitably engaged in crane 53 in order to lift the anchor from the bottom and to reposition it. Crane 53 is provided with a suitable winch (not· shown) in order to 1 i , , 42044 provide a lifting capability to the crane.

Tn accordance with such operation, the buoy catching Operation can be readily accomplished without repositioning the forward ends of the support guide bars 23. During buoy 5 retrieval operations, therefore, it is only required that the cradle 19 be lifted to the proximity of opening 49 in order to enable a crewman to affix the cable of crane 53 to the buoy anchor pendent line 30. Upon retrieval of one buoy, the cradle can simply be 10 lowered without repositioning the forward ends of the support guide bars.

In anchor repositioning operations, it is typical that the pendent line merely passes through a central opening in the buoy terminating an eye 75 atop the buoy. In these instances, it is desirable to reposition the anchor without raising the buoy on deck. Thus, desirably the crown block 77 of crane 53 is desirably located forward of the position of the buoy within cradle 19 as shown in Figure 6C. When the eye of the pendent line is fastened to the cable and 20 lifting is begun, the pendent line will tend to fall vertically from crown block 77 thus, displacing the buoy out of cradle 19. The buoy then simply slides do™ the pendent line 30 to the water as in Figure 6D and the repositioning of the anchor proceeds by raising the pendent line through the 2b buoy. When repositioning is complete, the pendent line is paid out from crane 53 and the retrieval mechanism is raised to permit the vessel to overrun the buoy and proceed to the next catching operation.

It will be readily appreciated that alternative apparatus 30 could be used in the place of that described in order to position and lift the retrieval apparatus. For example, the Π 42044 aft portion, of the retrieval apparatus could be affixed to the inboard hull surfaces opposite the position of the cradle 19 and provided with hydraulic cylinders which would be capable of positioning the. aft portion of.the 5 retrieval apparatus at the desired elevation, and would be further capable of elevating the cradle into proximity with opening 49 in deck 13 in order that access to the buoy might be had by a crewman. Indeed, the entire retrieval apparatus might be mounted in tracks at positions on the inboard 10 surfaces of the hulls approximately midway of the retrieval apparatus. Suitable means could then be provided to position the retrieval apparatus at any desired elevation relative to the waterline and further to elevate the retrieval apparatus in its entirety in order that access to a captured buoy or ^ other floating object might be had through opening 49 in the deck.

As stated above, the guide system as illustrated comprises primarily support guide bars 23 and. centering bars 33. Depending upon buoy configuration it may be desirable 20 and necessary to provide additional guide members to insure that the vessel will not overrun the buoy without capturing it in cradle 19. It will be noted that the anchor buoyS 47 which are illustrated are of a rubber construction and hence would not be expected to be damaged by striking the hulls of 25 the vessel at a point forward of the retrieval apparatus. Buoys constructed of metal or the like might damage the vessel if striking any portion of the hulls, and under such circumstances, a more extensive guide system, including guide members extending as far forward as the bow, might be 30 required in order to avoid damage to the vessel and to the 1 43044 buoy by virtue of such collision.

In Fig. 3 there is illustrated a further precaution which is desirable in construction of a buoy catching vessel of the type described. Fig. 3 illustrates a standard pro-5 peller propulsion system at the stern of each hull 11 of the catamaran vessel. , Propeller 55 is mounted on rotating shaft 83 which provides power. Immediately aft of the propeller is a standard type rudder 57. However, in view of the possibility that despite precautions with respect to design 10 of the retrieval apparatus, a buoy might be overrun by the retrieval apparatus, it is desirable to provide a propeller guard 59 as well as suitable propeller guide bars 84 at least on the inboard side but desirably on both inboard and outboard sides of each propeller mounted in the sterns of 15 hulls 11 to avoid the buoy or other objects striking the propellers.

Referring to Fig. 2 it will also be seen that, in accordance with a preferred design, each hull of the catamaran vessel is provided with a bow thruster In 20 order to enable the vessel to make rapid corrections to its course in approaching a buoy or other floating object for pickup. In heavy seas, it may be necessary to make corrections in course to avoid frontal collision with a buoy. When the vessel js under way, steering corrections by means of rudders 25 57 might not be sufficiently rapid particularly at low speeds. In the illustrated embodiment bow thrusters, are provided illustrated at 85- and 87 respectively/ in the forward portion of each hull. Through-the-hull bow thrusters comprising essentially a powered propeller in an opening 30 from the inboard to outboard surface of each hull can be used. 1 42044 It will be understood that the remainder of the vessel design illustrated can be standard vessel design and is herein illustrated but not described in detail. It will be further understood that alternative vessel designs may be 5 used. For example, pilot house 21 of the vessel might be positioned further aft, thereby enlarging the opening between the forward portions of the hulls. The retrieval apparatus might then be positioned in a forward position between the hulls in order that the pilot house » 10 might have a view of the buoy as it is being captured and retrieved. Alternatively, a U-shaped opening may be provided between the hulls in the aft portion of the vessel and the retrieval system positioned below this opening. 1

Claims (3)

1. 42044 at preselected levels relative to the waterline. 4. An apparatus as claimed in any preceding Claim, wherein the cradle of said retrieval apparatus has an open truss network construction including lower cradle 5 bars for supporting the object from underneath and upper retaining bars for holding the object in the cradle while the vessel is underway and providing unrestricted access to the object from above. 5. An apparatus as claimed in any preceding Claim, 10 including lifting means on the deck of said vessel for securing and lifting an object held within the cradle of said retrieval apparatus. 6. An apparatus as claimed in Claim 5, wherein said lifting means includes a crane and cable, said cable 15 being extendible to a captured object in said cradle from a point above and forward of said cradle. 7. An apparatus as claimed in any preceding Claim, including bow thruster means provided in the forward portion of each of said hulls. 3. Apparatus for capture of a floating object sub stantially as herein described with reference to and as shown in the accompanying drawings. Dated this 13th day of May 1975, ' TOMKINS & CO., ^ippHearpts1 Agents, (signed) yOr+'iC 5 Dartmouth Road, DUBLIN 6 1 42044 I. Apparatus for capturing a floating object which comprises a powered catamaran vessel having two spaced hulls, said vessel being suitable for manoeuvrable advance-5 ment through a body of water toward an object floating at the surface of the water; and retrieval apparatus disposed between said hulls for capturing and holding the retrieval object within said/apparatus while said vessel is under way comprising a cradle that provides support to the 10 underside of the object and unrestricted access to the object from above, and guide members which extend forwardly ' and outwardly of said cradle to direct the object away from said hulls and into said cradle, said retrieval apparatus being secured to the inboard surface of each said hull at a 15 position forward of said cradle and being movable in a ’ i vertical direction to a position below water level to permit capture of the object while said vessel is under way and to a position completely above the water level to alternatively permit said object to be raised out of the 20 water or permit said vessel to overrun the floating object.

2. An apparatus as claimed in Claim 1, wherein said guide members are pivotally secured at their forward ends to the inboard opposing surfaces of the hulls, and said retrieval apparatus includes means to move the pivot points of the guide members db /vertically relative to the waterline of said vessel to retrieval apparatus position said / relative to said waterline and a hoist to move said cradle in a vertical direction relative to said waterline about said pivot points.

3. An apparatus as claimed in Claim 2, wherein 30 said means to move said pivot points comprises vertical surfaces guide tracks disposed in said opposing hull/ with means for positioning said pivot points of said guide members