Patent Application
20200391835
The invention relates to a tug. More specifically, the invention concerns a tug having an all around towing system.
In harbours and restricted sailing areas, ships are usually assisted by one or more tugs. The ship and tug are connected by a towline and the tug manoeuvres in the required position to pull the ship. In addition to towing, the tug can also perform pushing operations.
Tugs in general have a fixed towing hook or towing winch on deck and the towline is connected to this equipment. Further an accommodation and wheelhouse are mounted on deck, thereby hindering the towline to rotate freely around.
A solution to enable free rotating all around in the horizontal plane is offered by various rotating towing installations. Examples include DE881312 (Schlepper für Schiffe by Buff 1951), NL1012977 (Ontwerp van sleepboot by M. van der Laan 1999) and NL1027414 (Sleepboot met verplaatsbare sleepinstallatie by Mampaeij 2006). These patents describe a 360° rotatable towing installation on either a circular track or an oval track, running on the outer side of the accommodation/wheelhouse. On this towing installation a towing hook or winch is fitted where the towline to the assisted ship is connected. Typical diameter or width of the towing installation is in the range of 66-100% of the tug's width. By moving the towing point to the ship's side, the heeling moment is reduced and capsizing risk minimized.
All around towing systems offer interesting functionality with regards to towing operations, but the design of the rail construction, the production, installation, repairs and maintenance involve high cost and also the design of the carriage involves high production cost. Further the whole installation is mounted on the deck of the tug and is subjected to the highly corrosive environment. The so-called carrousel tug (according to NL1012977) involves all around rail segments welded into the supporting structure, followed by machining to achieve a circular shape. The carriage is formed by a full circular outer ring with a large number of supporting wheels distributed over the whole circumference. The DOT tug (according to NL1027414) involves all around horizontal rail structure with two parallel supporting plates combining a large welding length and a solid structure without possibilities to easily modify, repair or exchange. The carriage is formed by two separate carriages with a complex stool and double hinge structure.
The object of the present invention is to provide an improved all around towing system on a tug which does not have the drawbacks described above, i.e. easy manufacturing of the rail and supporting construction, reduction of welding length, easy mounting and replacement of the rail construction, a simplified carriage construction without hinges and internal moving parts.
In one aspect, the invention provides an all around towing system for a tug comprising:
a heavy plate mounted on a deck of the tug;
an upper rail segment and a lower rail segment disposed on the upper and lower surfaces of an outer edge of the heavy plate, respectively;
a carriage movable along the upper and lower rail segments;
a set of bearing wheels arranged for guiding the carriage along the upper and lower rail segments;
characterized in that the heavy plate further comprises respective upper and lower grooves on the upper and lower surfaces of the heavy plate, and in that the upper and lower rail segments are respectively mounted in the upper and lower grooves of the heavy plate.
This object is achieved by the design of the rails and the carriage. The rails consist of separate segments mounted partially inside a groove in a heavy plate which is a thick steel plate. The heavy plate is mounted on the deck of the tug in a primarily horizontal arrangement and extends all around outside the supporting structure. In this heavy plate on both the upper side and the lower side grooves are machined, wherein the rail segments can be fitted. To transfer the sideward towing force, the grooves only require relative small depth. As example a groove in range of 10-20 mm can be used for a 80 mm thick rail. Larger and smaller sized rails will scale in similar ratio. The carriage is formed by an ‘U’-shaped structure around the edge of the heavy plate and equipped with bearing wheels on both upper and lower surfaces of the carriage. These bearing wheels are in contact with the upper and lower rail segments and are positioned on the inner surface of the carriage to transfer the outward force from the towline. The towline from the assisted ship is connected to the carriage by any suitable means. This can be for example a towing hook or a towing winch.
According to further advantageous design, the outer circumferences of the upper and lower rail segments have the same outer and inner diameter in that the upper and lower rail segments are laterally aligned to each other. The grooves are mirrored around the centre line of the heavy plate. For ease of mounting and strength support, the upper and lower rail segments are fitted with bolt or threaded construction to connect to each other through the heavy plate in the grooved section.
According to another advantageous design, the rails on the upper and lower side are moved along the circumference to produce an overlapping structure in order to increase the bending strength and structural stability. The upper rail segment can for example extend halfway above the lower rail segment and similarly the lower rail segment extends halfway below the adjacent upper rail segment.
According to another advantageous design, the bolted connections formed between the upper and lower rail segments and the heavy plate are positioned along the inner curvature of the rail segments to prevent the rail segments from rotating out of the groove by the outward load. As example the bolted connection is at approximately 15-40% of the rail width measured from the inner curvature of the rail segments.
According to another advantageous design, the upper groove has a smaller diameter than the lower groove, preferably the outer edge of the upper groove has a smaller diameter than the inner edge of the lower groove. Hereby the thickness of the heavy plate can be reduced. In case of significant difference between the groove diameters, the lever between upper and lower rail increases and counters up and down rotation around the outer edge of the heavy plate. This can be advantageous when installing larger towing components on the carriage.
According to another advantageous design, the carriage has two rigid parts.
Preferably each rigid part of the carriage includes one connecting or guiding structure for connection to the towline or the separate cable structure. The marginally flexible construction can be a connection steel structure allowing small deformation in the range of a few mm, thereby allowing each rigid part to flex marginally from the other rigid part and to follow small deformations of the rails. These deformations can have various reasons, e.g. production tolerances, small plastic deformations, wear on rail surface.
According to another advantageous design, the carriage is fitted with two connection or guiding structures positioned at a distance of at least 20% of the carriage length measured from half length of the carriage. The towline from the towed ship divides at certain distance from the carriage (e.g. forming a triangle shape with each angle 60°) into two parts and both parts extend to either connection structures and thereby distribute the load (evenly) over the circumference of the contacting rail segments.
According to another advantageous design, the connection structures are replaced by guiding structures, the split towline runs on the outer side of the guiding structures and around the guiding structures towards the centre. These guiding structures can consist of a fixed curved smooth surface or a rolling surface. At the centre of the carriage both cable ends can be connected to each other or fixed to the carriage. Further the connection can also involve a release system to allow both ends to part and move outward around the guiding structures.
According to another advantageous design, the towline is connected to a separate cable structure running through or around the guiding structures.
According to another advantageous design, the carriage consists of two rigid parts which are connected to each other with a marginally flexible construction. Each rigid part consists of two main upper bearing wheels on the upper surface of the carriage and two lower main bearing on the lower surface of the carriage.
According to another advantageous design, the carriage consists of two rigid parts, which are connected to each other with a flexible construction. The rigid parts are similar to the previous design, but the connecting structure allow significant flexing in the range of a few cm or more. This construction can be composed of all kind of flexing structures, hinges, sliding parts. Hereby each rigid part can flex compared to the other rigid part and thereby follow various significant changes in the radius of the rails. This will not only allow for small deformations of a few mm, but also allows to move along an oval/elliptical rail shape. In case of the towline or separate cable structure is connected to a connection structure on each rigid part, the resultant force pushes the rigid parts together. In case the towline or separate cable structure runs through the guiding structures on each rigid part towards the centreline, the resultant force again pushes both rigid parts together. In both cases a significant push force is generated by the towline load and the connection does not need to generate pull forces. A simple flexible buffer like structure between both rigid parts is sufficient.
According to another advantageous design, the main bearing wheels consist of at least four wheels on the upper and inner half surface of the carriage and at least four wheels on the lower and inner half surface of the carriage. Also five, six, seven or even eight wheels on either sides can be applied. The bearing wheels are preferably equally distributed over the carriage length to distribute the force properly to the upper and lower rail segments.
According to another advantageous design, the main bearing wheels have a rotating axis rectangular to the heavy plate. These bearing wheels are positioned on the inner surface of the carriage to transfer the outward pull from the carriage to both the force from the upper bearing wheels to the upper rail segment and simultaneously from the lower bearing wheels to the lower rail segment.
According to another advantageous design, the main bearing wheels are fitted with a flange, the upper main bearing wheel has the flange on the upper side corresponding to the upper level of the rail segment. The same arrangement applies to the lower side of the lower main bearing wheel. Hereby the carriage is positioned not only in radial outward direction by the bearing wheels, but also in vertical direction by the flanges.
According to another advantageous design, the main bearing wheels are fitted with flanges whereby the main bearing wheels take the radial load and the flanges take the load parallel to the rotating axis.
According to another advantageous design, in addition to the main bearing wheels, the additional supporting wheels are mounted on the carriage to position the carriage properly on the upper and lower rail segments, both in radial inward direction and against up and down rotation around the outer edge of the heavy plate. As a practical example a number of additional wheels are positioned on the outer side of the upper and lower rail segments with the rotating axis rectangular to the heavy plate. Hereby the upper and lower rail segments are enclosed between the main bearing wheels and the additional wheels on the inner and on the outer side ensuring proper guidance. By mounting these additional wheels both on the upper side against the outer side of the upper rail segment and on the lower side against the outer side of the lower rail segment the carriage moves smoothly along the rail segments with little up and down rotation. To facilitate mounting and adjustment, the additional bearing wheels on the outside of the rail segment may be fitted with an eccentric bush around the shaft. By turning the eccentric bush, the wheel may be positioned accurately near the rail segment surface. The additional bearing wheels positioned on the outside of the rail segment may be fitted with flanges, the upper main bearing wheel with flanges on the upper side and the lower main bearing wheel with flanges on the lower side. In case of a towline at a large upward angle (e.g. in case of a ship with a high deck or in case of the tug heeling sideward with a large angle), the flanges of the lower outer wheels will assist the flanges of the lower inner wheels in sharing the vertical load.
According to another advantageous design, additional wheels are mounted on the upper and outer half surface of the carriage in contact with the outer side of the upper rail segment to take the vertical downward load. This load consists of a combination of gravity load of the carriage and towline load.
According to another advantageous design, additional wheels are mounted on the lower and outer half surface of the carriage in contact with the outer side of the lower rail segment to take the vertical upward load. This load consists of a combination of gravity load of the carriage and towline load.
According to another advantageous design, the carriage consists of a certain length around the outer circumference of the rail segments to distribute the local towline load over part of the rail length. The length of the carriage will be in the range of at least 5% preferably in range of 10-20% of the outer circumference of the rail segments. Along the upper part and the lower part wheels are mounted along the circumference to transfer the load from the carriage to the rail segments.
According to another advantageous design, the production process of the rail segments can be done by cold rolling a straight bar over a number of rollers in a heavy hydraulic press to form the bar into the requested curvature by plastic deformation. This allows easy production with little material losses and a high accuracy of the rail width to match the width of the groove and the distance between the rollers on the inside and the outside of the rail. Also, other similar mechanical presses can be considered to shape the straight rail into the requested curvature. In case of large rail segments additional heating of the rail material may be used to perform part heated rolling.
The present invention will become more clearly understood from the following description of the embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiment and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention, the scope of which is to be determined by the set of appended claims.
The tug 1 represented in
The tug 31 represented in
Further, a set of additional outer wheels 53, 54 are provided on the upper and lower surfaces of the carriage 46. The carriage frame 46 is fitted with additional upper wheels 53 and additional lower wheel 54. The additional upper wheels 53 are arranged and positioned on the upper and outer half surface of the carriage 46 in contact with the outer side of the upper rail segment 42. The additional lower wheels 54 arranged and positioned on the lower and outer half surface of the carriage 46 in contact with the outer side of the lower rail segment 44. The additional upper and lower wheels 53, 54 are each equipped with a flange 55 of upper wheel 53 and the flange 56 of lower wheel 54, respectively. Also, the additional upper and lower wheels 53, 54 have a vertically rotating axis 57.
The right part 61 of the carriage 46 is shown transparent with internals and showing the main upper bearing wheels 47, the additional upper wheel 53 and the additional lower wheel 54. The left rigid part 62 of the carriage 46 is shown solid with main upper bearing axle 66 and an additional upper axle 67.
Although the invention has been described above with reference to a preferred embodiment, numerous modifications may be made without departing from the scope of the present application. The all around towing installation may be constructed in all kind of different arrangements of rails, wheels and rollers both on fully circular shapes and on oval or non-circular shapes. The design is intended for unrestricted all around operation, but the design may be used for only part rotation, e.g. rails over a half circle from one side to the other over the aft deck.
Instead of upper and/or lower rail segments, the heavy plate (groove) surface may also be treated to increase the hardness (or by adding material) and thereby allowing to operate the bearing wheels directly on the heavy plate without the need for additional rails.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI 2018700682 | Feb 2018 | MY | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/051068 | 2/11/2019 | WO | 00 |
