Push-Boat to a Barge

Background and Field of the Invention

The invention relates to a push-boat for pushing a barge, a barge and method for securing a push-boat to a barge.

It is common to use a barge for transporting cargo or freight in canals, rivers, lakes or the open sea. The barge may be self-powered or manoeuvred by another boat. For example, one traditional way of manoeuvring a barge is by towing it using a tugboat with towing ropes connected between the barge and the tugboat. However, it is not easy to manoeuvre the barge using the tugboat, especially when the barge needs to turn or when the barge is used in narrow and shallow water areas. Further, the barge is usually towed at low speeds which mean that the tugboat is not suitable for maneuvering the barge over long distances.

Another traditional way is to push the barge by using a push-boat i.e. to form a pusher-barge combination but this way is also prone to accidents as the push- boat may not maneuver the barge effectively.

It is an object of the present invention to provide a push-boat for pushing a barge, a barge and method of securing a push-boat to a barge which addresses at least one of the disadvantages of the prior art and/or to provide the public with a useful choice.

Summary of the Invention

In a first aspect of the present invention, there is provided a push-boat for pushing a barge; comprising a pair of port coupling mechanisms arranged to couple the push-boat's port to the barge, centre-to-centre of the pair of the port coupling mechanisms being at a first distance apart; and a pair of starboard coupling mechanisms arranged to couple the push-boat's starboard to the barge, centre-to-centre of the pair of the starboard coupling mechanisms being at a second distance apart; each of the first and second distance is at least half of the push-boat's length between the push-boat's bow and stern.

The term "the push-boat" is used in a general sense to include any water craft or vessel for pushing a barge.

An advantage of the described embodiment is that this gives the push-boat more stability when pushing the barge. This also ensures a firm, safer and secure coupling between the push-boat and the barge and enables both to be operated as if they are a single unit.

Preferably, the first and second distances may be the same. Each of the port and starboard coupling mechanisms may include an extendable and retractable engagement member for engaging with a barge coupling mechanism. The engagement member may include a plurality of engagement pads with each engagement pad spaced from another engagement pad. Preferably, there may be nine engagement pads.

In a second aspect of the invention, there is provided a barge for transporting cargo, comprising: a push-boat holding void at the barge's stern for receiving a push-boat to enable the push-boat to push the barge; a stern portion arranged at each side of and defining the push-boat holding void, the stern portions including a first pair of barge coupling mechanisms for coupling to corresponding port coupling mechanisms of the push-boat and a second pair of barge coupling mechanisms for coupling to corresponding starboard coupling mechanisms of the push-boat, wherein centre-to-centre of the first pair of the barge coupling mechanisms is at a first barge distance and centre-to-centre of the second pair of the barge coupling mechanisms is at a second barge distance; and wherein each of the first and second barge distance is at least half of the push-boat's length between the push-boat's bow and stern. In the second aspect, preferably, the first and second distances may be the same. Each of the first and second pairs of barge coupling mechanisms may include an elongate connecting slot arranged to be engaged selectively by an engagement member of the push-boat at one of a plurality of engagement positions along the elongate connecting slot. Each of the first and second pairs of barge coupling mechanisms may also include a plurality of discrete connecting apertures arranged to be engaged selectively by an engagement member of the push-boat, each discrete connecting aperture having a corresponding engagement position for engagement by the engagement member.

Preferably, the plurality of discrete connecting apertures of each of the barge coupling mechanisms is disposed within a movable frame and the movable frame is movable in a coupling channel. The coupling channel may include guide tracks for slidably engaging sides of the movable frame. The barge may further comprise a hoisting device coupled to a respective movable frame for lifting or lowering the movable frame linearly. Preferably, the hoisting device is pivotably connected to the respective movable frame. The hoisting device may include a stand for mounting to a deck of the barge, a cylinder body pivotably connected to a support extension of the stand; and a piston movable relative to the cylinder body, and wherein the piston is pivotably connected to the movable frame.

In a third aspect, there is provided a pusher-barge comprising a push-boat according to any of the features relating to the first aspect and a barge according to any of the features relating to the second aspect.

In a fourth aspect, there is provided a method of securing a push-boat to a barge, the barge's stern having stern portions arranged at each side of and for defining a push-boat holding void, which is for receiving the push-boat and to enable the push-boat to push the barge; the method comprising receiving the push-boat in the push-boat holding void of the barge and between the respective stern portions; coupling the push-boat's port side to one of the stem portions using a first pair of coupling mechanisms; and coupling the push-boat's starboard side to the other stem portion using a second pair of coupling mechanisms; wherein centre-to-centre of the first pair of coupling mechanisms is at a first distance and centre-to-centre of the second pair of coupling mechanisms is at a second distance; and wherein each of he first and second distance is at least half of the push-boat's length between the push-boat's bow and stern.

Preferably, the first and second pair of coupling mechanisms may include a pair of port coupling mechanisms and a pair of starboard coupling mechanisms mounted to the push-boat. Each of the pair of port coupling mechanism and the pair of starboard coupling mechanism may include an engagement member; and wherein the method further includes extending each of the engagement members linearly to engage with respective barge coupling mechanisms of the barge.

In a fifth aspect of the invention, there is provided a barge for transporting cargo, comprising: a push-boat holding void at the barge's stern for receiving a push-boat to enable the push-boat to push the barge; a stern portion arranged at each side of and defining the push-boat holding void, the stern portions including a plurality of barge coupling mechanisms for coupling to corresponding boat coupling mechanisms of the push-boat; each one of the plurality of barge coupling mechanisms includes a movable frame having at least one connecting aperture for selective engagement by one of the boat coupling mechanisms; a number of hoisting devices corresponding to the plurality of barge coupling mechanisms, with each hoisting device being arranged to lift or lower the respective movable frame.

Preferably, each movable frame may include a plurality of discrete connecting apertures arranged to be engaged selectively by the corresponding boat coupling mechanism of the push-boat, each discrete connecting aperture having a corresponding engagement position for engagement by the boat coupling mechanism. The movable frame may be movable in a coupling channel. Preferably, the coupling channel includes guide tracks for slidably engaging sides of the movable frame.

Preferably, the hoisting device may be pivotably connected to the respective movable frame. The hoisting device may include a stand for mounting to a deck of the barge, a cylinder body pivotably connected to a support extension of the stand; a piston movable relative to the cylinder body, and wherein the piston is pivotably connected to the movable frame.

Advantageously, each hoisting device may be operable to lift or lower the respective movable frame when each of the at least one connecting aperture is engaged by the corresponding boat coupling mechanisms to enable the lifting or lowering of the push-boat with respect to the barge.

The invention may also include a method of operating the barge of the fifth aspect and indeed, this forms a sixth aspect of the invention in which the method includes, with each of the at least one connecting aperture engaged by the corresponding boat coupling mechanisms, operating each of the hoisting devices to lift or lower the respective movable frames to lift or lower the push- boat with respect to the barge.

According to a seventh aspect of the invention, there is provided a barge for transporting cargo, comprising: a push-boat holding void at the barge's stern for receiving a push-boat to enable the push-boat to push the barge; a stern portion arranged at each side of and defining the push-boat holding void, the stern portions including a plurality of barge coupling mechanisms for coupling to corresponding boat coupling mechanisms of the push-boat; each one of the plurality of barge coupling mechanisms includes a movable frame having a plurality of discrete connecting aperture for selective engagement by one of the boat coupling mechanisms; a coupling channel for receiving the movable frame and which enables the movable frame to be freely slidable relative to the coupling channel. It should be appreciated that features relevant to one aspect may also be relevant to the other aspects.

Brief Description of the Drawings

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a top plan view of a barge being coupled to a push-boat for pushing the barge according to a first embodiment of the invention;

Figure 2 is a side plan view of the push-boat and barge combination of Figure 1 with certain hidden features shown in broken lines;

Figure 3 is a close up plan view of a barge stern of the push-boat and barge combination of Figure 1 having four coupling mechanisms including port coupling mechanisms and corresponding barge coupling mechanisms;

Figure 4 is a side plan view of the barge stern of Figure 3 with certain hidden features shown in broken lines;

Figure 5a is an enlarged cross sectional view of one of the port coupling mechanisms with a piston rod in a retracted position;

Figure 5b shows the port coupling mechanism of Figure 5a with the piston rod in an extended position;

Figure 6 is a front view of the port coupling mechanism of Figure 5a;

Figure 7 is an enlarged top plan view of portion A of Figure 3 to show one of the barge coupling mechanisms more clearly;

Figure 8a is a front plan view of the barge coupling mechanism of Figure

7;

Figure 8b is a top view of the port coupling mechanism of Figure 5a and the top plan view of Figure 7;

Figure 9 is an enlarged top plan view of the barge stern of Figure 3 to show how the push-boat is coupled to the barge;

Figure 10 is an end view of the barge stern in a direction B of Figure 9; Figure 11 is a top plan view of a barge separated from a push-boat according to a second embodiment of the invention;

Figure 12 is a side plan view of a port coupling mechanism being used in the push-boat of Figure 11 ;

Figure 13 is a front plan view of the port coupling mechanism of Figure

12 in a direction E;

Figure 14 is an enlarged side view of the port coupling mechanism of Figure 12 and a barge coupling mechanism being used in the barge of Figure 11 ;

Figure 15 is a front view of the arrangement of Figure 14 in a direction G;

Figure 16 is a top plan view of the arrangement of Figure 15;

Figure 17 is a perspective view of the arrangement of Figures 14 to 16 but with the port coupling mechanism and the barge coupling mechanism in a different relative position;

Figures 18a and 18b illustrate similar views of Figure 14 but with the port coupling mechanism and the barge coupling mechanism in different coupling positions; and

Figure 19 is an enlarged end view of the push-boat and barge of Figure 11 , when they are coupled to each other.

Detailed Description of Preferred Embodiments

Figure 1 is a top plan view of a barge 100 being coupled to a push-boat 200 for pushing the barge 100. The barge 100 includes a barge deck 101 , a barge bow 102 and a barge stern 104 and a cargo holding area 106 for holding cargo 108 for transportation. The barge 100 includes a barge bridge 110 near the barge bow 102 which may be used for commanding the barge 100. The barge stern 104 includes a push-boat holding void 112 (see Figure 3) to correspond to a shape of the push-boat 200 and the void 112 is formed between two stern portions 114,116 of the barge 100 to create an inverted U.

Figure 3 is a close-up top plan view of the barge stern 104 of the barge 100 of Figure 1 in combination with the push-boat 200, and Figure 4 is a side view of the combination of Figure 3. The push-boat 200 has a bow 202 and a stern 204 and a length "L" between the bow 202 and the stern 204. The push-boat 200 includes a boat bridge 206 for commanding and controlling the push-boat 200. The push-boat 200 further includes a fender 208 at the bow 202 to minimize damage to the push-boat 200 and the barge 100 when the push-boat 200 is received in the void 112. Unlike traditional pusher-barge arrangements, in this embodiment, the stern portions 114,116 extend throughout almost the entire length "L" of the push-boat 200. In other words, the push-boat 200 is almost received within the void 112. In this embodiment, it may be considered that at least 90% of the length "L" of push-boat 200 is received within the void 112 such that the push-boat 200 and the barge 100 may operate as one unitary vessel.

The barge 100 and the push-boat 200 have a plurality of coupling mechanisms to couple the barge 100 to the push-boat 200 or vice versa. Specifically, the push-boat 200 includes a plurality of boat coupling mechanisms for engagement with corresponding barge coupling mechanisms and in this embodiment, there are four boat coupling mechanisms 210,212,214,216. A pair of the coupling mechanisms 210,212 are mounted to the push-boat's port 218 (and thus, referred to as "port coupling mechanisms") and the other pair of the coupling mechanisms 214,216 are mounted to the push-boat's starboard 220 (and referred to as "starboard coupling mechanisms") and the coupling mechanisms 210,212 at the port 218 are in registration respectively with the coupling mechanisms 214,216 at the starboard 220. It should be appreciated that the pair of port coupling mechanisms 210,212 are arranged at a distance apart and centre-to-centre distance between the pair of port coupling mechanisms 210,212 may be regarded as D1. Similarly, the pair of starboard coupling mechanisms 214,216 is arranged at a distance apart and centre-to-centre distance between the pair of starboard coupling mechanisms 214,216 may be regarded as D2. Specifically, it has been found that the distance D1 and D2 is each half or more than half of the length "L" (i.e. = L/2) in order for the push- boat 200 to push and manoeuvre the barge 100 more effectively. Indeed, this would also provide stability to the push-boat 200 and barge 100 combination since the both are effectively operating as one integral unit.

Figure 5a is a close-up cross sectional side view of one of the port coupling mechanism 210 (referred to as a first port coupling mechanism to distinguish from the other three coupling mechanisms) and Figure 6 shows a front view of the first port coupling mechanism 210. Since the rests of the port and starboard coupling mechanisms have the same structure, only one will be described. The first port coupling mechanism 210 has a body 222 mounted to a deck of the push-boat 200 and at the port side 218. The first port coupling mechanism 210 includes a hydraulic cylinder 224 having a cylinder barrel 226 and a piston rod 228 which is actuated by a hydraulic pump (not shown) to move linearly relative to the cylinder barrel 226 (or body 222). The first port coupling mechanism 210 includes an engagement member support frame 230 attached to the piston rod 228 and linear movement of the piston rod 228 thus extends or retracts the engagement member support frame 230. Figure 5a shows the piston rod 228 in a retracted position whereas Figure 5b shows the piston rod 228 in an extended position. It should be appreciated that a lock may be activated when the piston rod 228 is in the extended position to prevent movement of the piston rod 228.

The first port coupling mechanism 210 also includes an engagement member 232 and in this embodiment, the engagement member 232 includes a plurality of engagement pads 234 regularly spaced, from each other to form a square array as shown in Figure 6 and each of the engagement pads 234 are mounted to the engagement member support frame 230 using fasteners 236. Each of the engagement pads are made of elastomeric material such as hard rubber and preferably, the engagement pads have "tread" similar to tyre tread to ensure that the engagement pads make good friction contact. Further, although there can be any suitable number of engagement pads, it has been found that nine engagement pads 234 are optimum and it provides the best frictional grip. Control of the first port coupling mechanism 210 (and the other three coupling mechanisms 212,214,216) is via a control panel (not shown) at the boat bridge 206. The first port coupling mechanism 210 is arranged to couple to or engage a respective barge coupling mechanism and in this embodiment, this is in the form of a first connecting slot 118 (see Figure 3 for the other three connecting slots 120, 122, 124). Figure 7 is an enlarged top plan view of portion A of Figure 3 to show the first connecting slot 118 more clearly and Figure 8a is a front view of the first connecting slot 118 of Figure 7. The first connecting slot 118 includes a rear engagement wall 126 and two side walls 128,130 orthogonal to and adjoining respective ends of the rear engagement wall 126 to form an elongate continuous channel which defines the first connecting slot 118. The rear engagement wall 126 includes a steel plate. It should be appreciated that spacing between the two sidewalls 128,130 is arranged to receive the engagement member 232 of the first port coupling mechanism 210 and this is shown more clearly in Figure 8b. In Figure 8b, a top view of the first port coupling mechanism 210 (with the piston rod 228 in the retracted position) is shown together with a top view of the first connecting slot 118 of Figure 7. When the piston rod 228 is extended, the engagement member 232 of engages with the rear engagement wall 126 and the width of the engagement member 232 is such that it fits between the two side walls 128,130 of the first connecting slot 118. In this way, any relative movement between the first port coupling mechanism 210 and the first connecting slot 118 (for example, due to bad weather and/or other pressures from hogging or sagging etc) the movement of the first port coupling mechanism 210 is restricted by the two side walls 128,130. Therefore, a much safer and steadier coupling is achieved.

Since the first connecting slot 118 includes the elongate continuous channel, this provides a plurality of engagement positions at which the first port coupling mechanism 210 may selectively engage therewith depending on a relative position of the push-boat 200 and the barge 100 (for example, the barge 100 may be carrying load and has a greater displacement than without load and the engagement position at which the first port coupling mechanism 210 engages the first connecting slot 118 would be higher than another engagement position when the barge 100 is not carrying any load). In this way, this enables the first port coupling mechanism 210 to frictionally engage the first connecting slot 118 firmly at a selected one of the plurality of engagement positions depending on the relative positions of the barge 100 and the push-boat 200 and this is illustrated more clearly in Figures 9 and 10.

In Figure 9, the piston rods 228,240,242,244 of the four boat coupling mechanisms 210,212,214,216 are extended linearly to exert respective engagement forces on the corresponding connecting slots 118,120,122,124. In this embodiment, each of the port coupling mechanisms 210,212 is in alignment with one of the corresponding starboard coupling mechanisms 214,216 so that when the port and starboard coupling mechanisms 210,212,214,216 are coupled to the respective barge coupling mechanisms (i.e. the connecting slots 118,120,122,124), the engagement force asserted by one of the port coupling mechanisms 210,212 is countered by a similar engagement force asserted by one of the starboard coupling mechanisms 214,216. For example, if the engagement force asserted by the first port coupling mechanism 210 is F1 , this is countered by a similar engagement force F2 asserted by the first starboard coupling mechanism 216. Similarly, if the engagement force asserted by the second port coupling mechanism 212 is F3, there is also a similar engagement force F4 asserted by the second starboard coupling mechanism 214. In this way, the push-boat 200 may be considered as being locked or secured to the barge 100 and may move like a single unit.

Figure 10 illustrates two relative positions C and D between the push-boat 200 and the barge 100. For example, in position C, the push-boat 200 pushes the barge 100 to a dock for loading with load or freight and retracts the port and starboard coupling mechanisms 210,212,214,216. In position C, the push-boat 200 is further away from the barge deck 101 than in position D because the barge 100 is not carrying load and thus, there is lesser displacement. When the barge 100 is loaded with the freight, the barge's displacement is greater and this changes the relative position of the barge 100 and the push-boat 200. Specifically, in position D, the push-boat 200 is now higher and nearer to the barge deck 101 of the barge 100 than in position C, and in position D, the port and starboard coupling mechanisms 210,212,214,2 6 are actuated to extend the respective piston rods to assert corresponding engagement forces F1 ,F2,F3,F4 against the connecting slots 118,120,122,124. In this way, the push-boat 200 is locked together firmly with the barge 100 for the push-boat 200 to push the (loaded) barge 100 to its destination.

The barge 100 and the push-boat 200 combination (commonly called a "pusher- barge) is particularly advantageous as it allows the combination to be used in open seas or oceans and not just in rivers or costal services. With the push- boat 200 almost totally inserted into the barge 100 (i.e. in the push-boat void 112), this provides greater stability and safety and the push-boat 200 may push the barge 100 at a faster speed. Indeed, it is understood that the speed might be increase by 10%-20%. Further, the gap between the push-boat 200 and the barge 100 might be less than 150mm or it can be as small or narrow as possible. Also, the push-boat 200 and the barge 100 combination requires a smaller turning radius which is useful for maneuvering narrow water regions, and piers etc. The use of the boat coupling mechanisms 210,212,214,216 and the barge coupling mechanisms 118,120,122,124 enables the barge 100 and the push-boat 200 to be coupled together closely and operate as a single unit and this enables the movement of the barge 100 by the push-boat 200 forward or backwards to be stable even in rough weathers (strong/high sea waves) and/or pressures from bogging and sagging etc.

The engagement member 332 for the first port coupling mechanism 210 (and indeed, in all the engagement members of the port and starboard coupling mechanisms) may not be a square array and may take other shapes and sizes such as what is being described in the second embodiment.

Figure 11 shows part of a barge 1100 and a push-boat 1200 separated from the barge 1100 according to a second embodiment of the invention and like parts/features as the first embodiment will use like reference numerals with the addition of 1000. The barge 1100 includes a barge deck 1101 , a barge bow (not shown), a barge stern 1104 and a cargo holding area (not shown). The barge stern 1104 has an inverted U-shape to create a push-boat holding void 1112 and just like the first embodiment, the push-boat holding void 1112 is arranged to receive the bow 1202 of the push-boat 1200 and almost the entire push-boat 1200 between the two stern portions 1114,1116. Similar to the first embodiment, the stern 1204 of the push-boat 1200 is almost flushed with edges of the two stern portions 1114,1116 when the push-boat 1200 is properly engaged with the barge 1100 (see Figures 1 and 2 for example).

The push-boat 1200 and the barge 1100 includes a plurality of coupling mechanisms and in this embodiment, the plurality of coupling mechanisms include four boat coupling mechanisms 500,502,504,506 mounted to the push- boat 1200 and four barge coupling mechanisms 600,602,604,606 mounted to the barge 1100 which cooperate with the four boat coupling mechanisms 500,502,504,506 respectively to couple the push-boat 1200 to the barge 1100. Similar to the first embodiment, two of the boat coupling mechanisms 500,502 are mounted to the port side 1218 (and thus, appropriately referred to as the port coupling mechanisms 500,502) and two of the boat coupling mechanisms 504,506 are mounted to the starboard 1220 (and thus, appropriately referred to as the starboard coupling mechanisms 504,506). All the four boat coupling mechanisms 500,502,504,506 are similar to each other and thus, one of them will be described and this is referred to as the first port coupling mechanism 500 and an enlarged side view of this is shown in Figure 12, and Figure 13 is a front view of the first port coupling mechanism 500 of Figure 12 in the direction E. Similar to the first port coupling mechanism 210 of the first embodiment, the first port coupling mechanism 500 of the second embodiment has a body 508 mounted to a deck of the push-boat 1200 at the port side 1218. The first port coupling mechanism 500 includes a hydraulic cylinder 510 having a cylinder barrel 512 and a piston rod 514 which is actuated by a hydraulic pump to move linearly relative to the cylinder barrel 512 (similar to the first embodiment). The first port coupling mechanism 500 further includes an engagement member support frame 516 attached to the piston rod 514 and linear movement of the piston rod 514 thus extends or retracts the engagement member support frame 516. The first port coupling mechanism 500 also includes an engagement member 518 mounted to the engagement member support frame 516 for engagement with one of the barge coupling mechanisms 600. Unlike the engagement member 232 of the first embodiment, the engagement member 518 of the second embodiment is circular in shape and is a single piece of moulded material mounted to the engagement member support frame 516 using fasteners 520. The moulded material is preferably elastomeric material such as hard rubber. Further, the first port coupling mechanism 500 includes a fastening pin 522 to minimize buckling of the cylinder barrel 512 when the engagement member 518 is in an engaged position. The actuation of the first port coupling mechanism 500 (and the other coupling mechanisms 602,604,606) is via a control panel (not shown) at the boat bridge 1206.

The first port coupling mechanism 500 is arranged to be engaged to one of the barge coupling mechanism (referred to as the first barge coupling mechanism 600) and the arrangement is shown in Figures 13 to 16 (i.e. when the push-boat 1200 is parked into the push-boat holding void 1112). Figure 14 is an enlarged side view of the first port coupling mechanism 500 of Figure 12 and the first barge coupling mechanism 600 of Figure 11. Figure 15 is a front view of the arrangement of Figure 14 in a direction G and Figure 16 is a top plan view of the arrangement of Figure 15. Figure 17, on the other hand, is a perspective view of the arrangement of Figures 14 to 16 (with certain features omitted) but with the first port coupling mechanism 500 and the first barge coupling mechanism in a different relative position as that illustrated in Figure 14.

Unlike the first embodiment, the first barge coupling mechanism 600 includes a plurality of discrete connecting apertures 608 disposed within a movable frame 610 and in this embodiment, there are upper, intermediate and lower connecting apertures 608a,608b,608c arranged end-to-end and in a vertical line. Each of the upper, intermediate and lower connecting apertures are defined by a rounded attachment frame 610a, 610b, 610c adapted to receive the circular engagement member 518 of the first port coupling mechanism 600. In other words, the engagement member 518 of the first port coupling mechanism 600 selectively engages one of the upper, intermediate and lower connecting apertures 608a,608b,608c depending on the relative position of the barge 1100 and the push-boat 1200 (for example, Figure 14 shows the first coupling mechanism in a position to engage the upper connecting aperture 608a, whereas Figure 17 illustrates the first coupling mechanism in a position to engage the lower connecting aperture 608c).

The barge 1100 further includes a coupling channel 612 arranged to receive the movable frame 610 and the coupling channel 612 includes guide tracks 613 for holding sides of the movable frame and which enables the movable frame 610 to slide relative to the coupling channel 612 (and thus, the coupling channel 612 is longer than the movable frame 610). The coupling channel 612 includes a stopper 614 for cushioning the impact of the movable frame 610 when a bottom end 616 of the movable frame 610 reaches an end of the coupling channel 612.

The barge 100 further includes a number of hoisting devices 618 and one of this is shown in Figures 14 to 17. The hoisting device 618has a stand 620 mounted to the barge deck 1101 and a hoisting cylinder 622 coupled to a support extension 624 of the stand 620 via a first pivot connection 625. The hoisting cylinder 622 includes a cylindrical body 626 and a hoisting piston 627 housed in the cylindrical body 626 and the hoisting piston 627 is actuated by a barge hydraulic pump (not shown) to move or slide relative to the cylindrical body 626 such that the hoisting piston 627 extends or retracts into the cylindrical body 626. The hoisting piston 627 is connected to a top end 628 of the movable frame 610 via a second pivot connection 629 and actuation of the hoisting piston 627 would thus lift or lower the movable frame 610 (and thus, the connecting apertures 608) with respect to the coupling channel 612. It should be apparent that the pivoting movement of the first pivot connection 625 transverses the pivoting movement of the second pivot connection 629.

It should be appreciated that, with the movable frame 610 freely slidable relative to the coupling channel 612 (and when the hoisting device 618 is configured to allow this movement), and when the first port coupling mechanism 500 is engaged to one of the connecting apertures 608a,608b,608c, this is particularly advantageous since the relative position between the barge 1100 and the push- boat 1200 may be adjusted without the decoupling of the boat coupling mechanisms 500,502,504,506 from the barge coupling mechanisms 600,602,604,606. This may happen when the push-boat 1200 is coupled to the barge 1100 and the barge 1100 is not carrying any cargo but when cargo is loaded onto the barge 1 00, the displacement of the barge 1100 changes. Instead of decoupling the push-boat 1200 from the barge 1100 and re-coupling the coupling mechanisms, which may be time consuming and also challenging in extreme weather conditions, the position of the movable frame 610 slides freely which in turn lifts or lowers the push-boat 1200 relative to the position of the barge 1100 dependent on the displacement of the barge 1100. This is further explained in relation to Figure 18a and 18b, which shows the side view of the first port coupling mechanism 500 and the first barge coupling mechanism 600 of Figure 14. While Figure 14 shows the first port coupling mechanism 500 uncoupled from the upper connecting aperture 608a of the first barge coupling mechanism 600 (i.e. unlock position which is when the push-boat 1200 is disengaged from the barge 1100 or both are about to be coupled with each other), Figure 18a shows the first port coupling mechanism partially inserted into the upper connecting aperture 608a (termed an intermediate position) and Figure 18b shows the first port coupling mechanism 500 fully inserted and engaged with the upper connecting aperture 608a (termed as a locked position). When the push-boat 1200 is pushing the barge 1100, the first port coupling mechanism 500 is fully engaged with first barge coupling mechanism 600 and in this case, the first port coupling mechanism 500 is extended into the upper connecting aperture 608a in the locked position as shown in Figure 18b. When the push-boat 1200 and the barge 1100 arrives at a port, and the barge 1100 needs to be loaded with cargo, unlike conventional operations, there is no need to uncouple the push-boat 1200 from the barge 100. Instead, the first port coupling mechanism 500 is actuated and the piston rod 514 is retracted slightly to the intermediate position as shown in Figure 18a. As it can be appreciated, the first port coupling mechanism 500 is still partially engaged with the first barge coupling mechanism 600. In the intermediate position, the hoisting device 618 is configured in a "free adjustment" mode in that the hoisting piston 627 is freely slidable relative to cylindrical body 626. As explained earlier, this also means that the movable frame 612 is also freely movable with respect to the coupling channel 612. When cargo is loaded to the barge 1100, the barge's displacement changes relative to the push-boat 1200 and thus, the relative positions also changes. This is illustrated in Figure 9, which is an enlarged end view of the push-boat 1200 and barge 1100 combination of Figure 11 , when the push-boat 1200 is coupled to the barge 1100 (i.e. the boat coupling mechanisms 500,502,504,506 are engaged with respective barge coupling mechanisms 600,602,604,606) in the intermediate positions (as shown in Figure 18a) and when the barge 1100 is empty.

When cargo is loaded onto the barge 1100, this displaces the barge 1100 downwards and causes the push-boat 1200 to rise in the direction of arrows H with corresponding movements of the movable frames of the respective barge coupling mechanisms 600,602,604,606. With the free movement of the hoisting device 618, this means that the relative positions between the push-boat 1200 and the barge 1100 is adjusted automatically without a need to uncouple the push-boat 1200 from the barge 1100. Once the barge 1100 is loaded with the cargo and is ready to move off, the first port coupling mechanism 500 is actuated for the piston rod 514 to fully engage the first barge coupling mechanism 600 in the locked position as shown in Figure 18b before the push- boat 1200 pushes the barge 1100 to its destination.

The above procedure may also be used during unloading of the cargo. It should also be appreciated that whilst the explanation is based on the first port coupling mechanism 500 and the first barge coupling mechanisms 600, the description also applies to the other port and barge coupling mechanisms.

If regulations at a port does not allow the push-boat 1200 to be coupled to the barge 1100 during loading/unloading or if the push-boat 1200 needs to disengage to push another barge to the port, the push-boat 1200 may disengage form the barge and after the loading/unloading, the push-boat 1200 is re-coupled to the barge 1100. If necessary, the hoisting devices 618 of each of the coupling mechanisms 600,602,604,606 may be operated to actively lift or lower each of the movable frames of the barge coupling mechanisms 600,602,604,606 by operating the barge hydraulic pump to adjust the relative position of the push-boat 1200 and the barge 1100 before the port coupling mechanisms 500,502,504,506 engage with respective barge coupling mechanisms 600,602,604,606.

By having the movable frames movable freely within the coupling channels, this enables the relative positions of the push-boat 1200 and the barge 1100 to be adjusted "automatically" depending on the displacements and buoyancy of the push-boat/barge. Also, since the push-boat 1200 is firmly and securely coupled to the barge 1100, this enables the pusher-barge to function as a unitary vessel and as a result, the use of the push-boat 1200 may transform the barge 1100 to be considered as a self-propelling vessel. Indeed, with the push-boat 1200 substantially received within the barge 1100, a truly unitary vessel may be achieved and the push-boat is thus suitable for pushing barges of any shapes and sizes. The use of the hoisting device enables adjustment of the vertical positions of the discrete connecting apertures and this may be used for refinement of the positions of the apertures in order to connect with corresponding boat coupling mechanisms.

The hoisting devices 618 may also be useful when the push-boat 1200 needs to clear obstacles in the seabed such as rocks. In this respect, the hoisting devices 618 may be actuated to lift the movable frames 612 and thus, lifting the push-boat 1200 at the four coupling points formed between the port coupling mechanisms 500,502,504,506 and the respective barge coupling mechanisms 600,602,604,606. Once the push-boat 1200 clears the obstacle, the push-boat 1200 may be lowered to an optimum position relative to the barge 1100. The described embodiments should not be construed as limitative. For example, in the first embodiment, the engagement member 232 of the port and starboard coupling mechanisms 210,212,214,216 may come in other shapes and material. Similarly, the engagement member 518 of the second embodiment may also be adapted in a different shape and material. The port and starboard coupling mechanisms of both embodiments may use other forms of coupling or connection and not necessary the hydraulic pistons etc described. Also, it is envisaged that the specific examples of the boat coupling mechanisms and the barge coupling mechanisms may be interchanged. Using the first embodiment as an example, the boat coupling mechanisms (i.e. the port and starboard coupling mechanisms) 210,212,214,216 having the engagement members 232 may be mounted to the barge 100, instead of the push-boat 200 and similarly, the connecting slots 118,120,122,124 may then be disposed on the push-boat 200.

Also, in the second embodiment, it is preferred for each of the barge coupling mechanisms to have a number of discrete connecting apertures 608 but it is envisaged that only one connecting aperture may be used. In other words, there is at least one connecting aperture 608.

In the described embodiments, hydraulic pumps have been described to actuate the port coupling mechanisms as well as the hoisting devices but it is apparent that other types of pumps or motors may be used. Having now fully described the invention, it should be apparent to one of ordinary skill in the art that many modifications can be made hereto without departing from the scope as claimed.