Abstract:
A multiple destination cable ferry system where a marine vessel is towed by an underwater sled into its final destination over underwater tracks and transfer switches. The system is designed to be under total computer control in such a way that the towed vessel can be delivered to its final destination without requiring any human intervention aboard the vessel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the national stage entry under 35 USC 371 for PCT/IB2010/055586, filed Dec. 5, 2010. The contents of the foregoing application is incorporated herein by reference. 
     FIELD 
     This application is related to the field of cable ferries, more specifically to marine propulsion, steering and dynamic anchoring. 
     BACKGROUND 
     Cable ferries are vehicles used for crossing rivers and canals using cable system, which is connected to both sides of the shore. Cable system is usually a steel cable and may be located either under water or above water. Cable ferries are well known since middle ages and used by many civilizations. Since cable ferries may be towed by pulling the cable from either side of the shore, the ship or the barge do not need to be powered on its own. Since the route of the cable ferry is necessarily determined by the cable that tows the boat, its operation is not affected by weather elements like fog, wind or river currents. In some cable ferry applications the boat may have its own engine power to pull the cable in order to provide the necessary propulsion toward the destination. The mentioned examples of related art are intended to be illustrative rather than exclusive. Current cable ferry designs are well known to those who are skilled in art. 
     As the environmental consciousness of the world increases, there are attempts to utilize cable ferries more frequently in environmentally friendly ways. Askgaard, in his publication US2010/0233918 A1 teaches a way of using electrically operated flywheel for operating cable ferry for carrying people and vehicles for short distance transportation. 
     This application intends to increase versatility of the cable ferry by providing multiple destinations as well as computer controlled operation. 
     SUMMARY 
     This invention is about cable ferry system with multiple destinations which can be used to tow a marine vessel to its final destination through a system of guided cable, chain or tracks through electronically controlled switch mechanisms. Unlike a classical cable ferry, which is dragged into its final destination by a single cable, this invention uses multiple cable systems or tracks and different propulsion mechanisms to lead the cable ferry into one of the multiple destinations selected. The invention teaches different embodiments of achieving this purpose. In one of the embodiments of the invention, the cable ferry is towed by an underwater sled to its final destination where the sled is switched from one track to another under electronic guidance. In another embodiment of the invention, the underwater sled can be attached to a moving cable or chain mechanism, which is being pulled by other means. 
     The invention also teaches the method of transferring underwater sled from one track to another, which is necessary in order to direct the sled into different destinations. Unlike a railroad track which works in a two dimensional plane, the invention teaches a mechanism that works in three-dimensional space which can also handle tracks that crosses each other&#39;s path. The system is designed to operate under computer control, which not only controls the switches at suitable locations but also keeps track of location of other cable ferries in order to facilitate trouble free crossing at switch points. The tracks are allowed to cross each other&#39;s path and the computer keeps track of location of all towed cable ferries. The speed of the sled is periodically adjusted in order to avoid colliding with other sleds towing other cable ferries. 
     The invented system provides an environmentally friendly way of transportation in sea since the propulsion force of the sled may be provided by wind turbines placed alongside the cable ferry routes. Another notable advantage of the system may be the unmanned operation of the cable ferry. Purpose built cable ferries designed for transporting goods can be sent to desired destination without human controller on board without being affected by weather conditions. 
     The tracks or the chains that provide the propulsion for the cable ferry are submerged well below the underwater depth of ships that sail the sea in order not to interfere with the usual self-propelled marine traffic. The invention teaches different methods for laying tracks in shallow as well as deep-sea locations. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows the flow chart of the operation of the invention. 
         FIG. 2  shows the overall outlook of the system. 
         FIG. 3  shows the details of the switch system, which switches tracks. 
         FIG. 4  shows one particular embodiment of the switch as a sled go through the switch assembly. 
         FIG. 5  shows a preferred embodiment of the switch system. 
         FIG. 6  shows an embodiment of the invention where the tracks are anchored to an uneven sea bed. 
         FIG. 7  shows cross section of tracks and sleds for different embodiments of the sled and track. 
         FIG. 8  shows an embodiment of track system where tracks are made out of cables and a suitable sled arrangement for this embodiment. 
         FIG. 9  shows an embodiment of track system where tracks are made out of chains and a suitable sled arrangement for this embodiment. 
         FIG. 10  shows an environmentally friendly embodiment of the invention which tows submerged containers. 
     
    
    
     DESCRIPTION 
     Cable ferry is a simple and cost effective solution for crossing short straits of water. Since cable ferry does not need an engine on board for propulsion, the cost of the vessel is minimal. The navigation of the vessel is also not a problem since it gets dragged to its final destination; as a result usual whether elements like fog or currents do not affect operation of the vehicle. Another added advantage is in the efficiency of the cable ferry operation. Self propelled ships use propellers to turn engine motive power into trust. It is well known to the people skilled in the art of marine propulsion that there are many different types of losses when rotational movement of engine is converted into trust by way of propellers. Dragging the vessel by cable eliminates some of the energy loses caused by the propeller. Of course cable ferry suffers from different types of losses which is mainly caused by dragging a heavy cable, but overall arrangement is much more environmentally friendly since the power source of the cable ferry system do not need to be on the vessel. Motive power for cable ferry system can be stationery on the shore and can be provided by electrical energy which is clean and may be provided by renewable means like wind turbines. 
     The traditional cable ferry suffers from the fact that it is designed for short straights and travels from one point to another. In this invention what is proposed is a system which enlarges the scope of cable ferry into a digitally controlled highway for maritime traffic where marine vessels are dragged into their destinations by underwater track system. 
     The subject of invention is a cable ferry guidance system where a ferry is towed into its final destination by an underwater mechanism comprising cables, chains, tracks and digitally controlled switch mechanisms. The system retains all the advantages of the classical cable ferry but increases its versatility by making it possible to go into different destinations. Energy source for the system can come from renewable energy sources like wind turbines placed along the route of the cable ferry. The cable ferry used in the system can be a vessel floating over water or it may be a vessel submerged underwater. The system is applicable to any size maritime waters including sea, river or lake. 
     The cable ferry, which will be referred as “vessel” from now on, is towed by one or more sleds running on underwater tracks. In one embodiment of the system, the vessel is coupled to two sleds via cables where one of the sleds is located in front of the vessel and the other one is located at the back of the vessel. The front sled tows the vessel forward and the back sled is used for stopping the vessel when needed as well as preventing the vessel drifting away from the path of the track underneath. The two sleds work in unison to accelerate, steer and stop the vessel as the journey requires. The sleds are completely submerged underwater and placed over special tracks, which are anchored to the bottom of the sea. The underwater tracks where the sleds are running are placed well below the hull depth of maritime traffic in the region and normally do not interfere with the self-propelled maritime vessels operating in the vicinity. The depth of the underwater tracks is maintained at a specific depth regardless of how deep the waters along the path of cable ferry. Depending on how deep the seabed is, the underwater tracks are either laid on the seabed directly or attached to pillars raised on the seabed or anchored by chains to the seabed. The exact attachment mechanism depends on the depth of the sea. In shallow waters, it may be sufficient to place the tracks on pillars or on the seabed directly, whereas in deep waters it may be necessary to anchor the tracks to the bottom of the sea. The tracks are designed to be buoyant and have tendency to rise to the surface. As a result, the tracks needs be anchored to the seabed in order to avoid them going up to the surface of the water. In locations where the water is too deep, the length of the anchoring chain maintains the track at a specific depth. This fact is especially important for the manufacturability of the track system along the deep portions of the sea since tracks can be laid by simply placing weighs along the track and connecting tracks to the weights with suitable length anchor weights. 
     The sleds are designed to be physically engaged and attached to the underwater track. The sleds may also contain prime mover inside which may be electrically, hydraulically or pneumatically powered in order to provide the motive force. The power to the sled can be provided either by the towed vessel itself or by external means like stationery power generators in the vicinity through the tracks. 
     In order to direct the towed vessel into different destinations it is necessary to switch the sleds from one track to another as needed. This operation is achieved by electrically, pneumatically or hydraulically activated switch mechanism, which is controlled digitally under computer control. As the sled towing the vessel approaches to a switch location, the sled is interrogated by number of electronic sensing units placed along the track, which acquire the ID number of the approaching sled. Underwater communication methods that can be used for interrogation of the approaching sleds can be acoustical, ultrasonic or electromagnetic and it is well known to those who are skilled in this art. Since the destination information of the vessel is associated with the sled ID, the switch controller switches the incoming track to the proper outgoing track well before the sled arrives at the switch junction. After both bow and stern side sleds pass through the switching junction, the switch is ready to provide navigation to another incoming sled pair. 
     The switch mechanism is also designed to handle tracks that may cross each other&#39;s path. The electronic sensors inform the computer system that keeps track of all sleds operating in the vicinity of the switch and adjust the speed of the approaching sleds as required so that different pairs of sleds do not attempt to cross the switch at the same time. 
     The operation of the system will now be explained using figures. 
       FIG. 1  shows the block diagram of the operation of the system. In block  1 , vessel and destination information is entered into the system. In block  2 , vessel is mated with sleds and sled ID&#39;s are associated with the vessel information including destination. In block  3 , the sled and route information is distributed to the switches and other vessels through networking means. Block  4  shows the actions done as the sled moves forward on the track and approaches to a switch position. As the sled starts moving, it is interrogated by sensing units placed alongside the track and the switches are configured appropriately for the desired destination track. If the switch is currently blocked by another pair of sleds crossing the track, the information is provided to the other sled pair approaching the switch in order for them to slow down or stop their movement. This process is shown in decision block  5 . If switch is not currently being crossed by another sled pair, the actuators inside the switch are instructed to move into the appropriate position in block  6 . If the switch is occupied by other sleds crossing the switch, the incoming sled speed is adjusted by the system in order to operate in the most efficient manner which is shown in block  7 . 
       FIG. 2  shows the perspective appearance of the overall system where vessel  10  is attached to bow sled  17  which is connected to the front side of the vessel and stern sled  12  which is connected to the aft part of the vessel through cables  18  and  11 . Both sleds  12  and  17  are on track  14  which may be placed on pillars like  16  or anchored to sea bed by chains  13 . As the sleds  12  and  17  move over the track  14 , the position and sled ID&#39;s are interrogated by sensing units  22  and  15  positioned alongside the track  14 . Switch mechanism  23  directs the sled  17  approaching from the direction of  24  to track  21 . The system accepts tracks coming from other directions like  19  to cross tracks like  14 . Track  19  also has sensing units like  35  to sense the passing sleds. 
       FIG. 3  shows the details of the switch mechanism of a preferred embodiment where the incoming sled  17  is interrogated by the sensing unit  15 . Guide rail  23  is hinged at the position  21  and free to rate sideways with respect to the hinged pivot point  21  over the support assembly  24 . The actuation movement of actuator  22 , the guide rail  23  is aligned and locked by either track  25 , track  26 , or track  27 . Sensing unit  35  placed over the output track used to confirm when sled enters and leaves the right track. The mid portion  33  of the sled  17  is made from semi-flexible material which can conform to the shape of the track as the sled is running over the track. As a result of this compliance built into the sled, the sled can follow the guide rail  23  which is hinged at point  21 . 
       FIG. 4  shows how sled enters and leaves the switch in the preferred embodiment.  FIG. 4A  shows instant when the sled is approaching the guide rails of the switch. In  FIG. 4B  the sled mechanism is passing over the hinged portion of the switch and complies with the shape of the guide rail.  FIG. 4C  shows the sled at the end position of the switch as it leaves the switch mechanism. 
       FIG. 5  shows another view of the preferred embodiment of the switch mechanism where the incoming track  14 , guide rail  23 , actuator mechanism  24 , outgoing tracks  45 ,  46 ,  47  and crossing track  19  are attached to a single rigid platform  44 . The height of the crossing track  19  is lower than the height of the incoming track  14  and outgoing tracks  45 ,  46 ,  47  in such a way that passing sleds in either track  14  or  19  can do so without snagging on the other tracks. Crossing track  19  also has sensing input  35  to detect passing sleds. 
       FIG. 6  shows an embodiment of the system where the sea bed has uneven depth along the path of the track and how the tracks are attached to sea bed in deep locations. In locations where the sea level is not too deep, short length anchoring chains like  18  attach the track  14  to the sea bed. In locations like  19  where the sea level is deep, the anchoring chain length is longer to compensate for the difference in depth. Track  14  is designed to be buoyant, so it needs to be anchored to sea bed in order to keep the tracks suspended in water. 
       FIG. 7  shows several embodiments of the track cross sections and the sleds.  FIG. 7  A shows a track with rectangular cross section  14 , and the sled assembly  17 . Track is attached to anchor chain  19  from the bottom in such a way that movement of the sled along the track is not hindered by the anchor connections.  FIGS. 7B and 7C  shows tracks with circular and triangular cross sections and the suitable sled assembly for them. 
       FIG. 8A  shows another embodiment of the track and switch system where the tracks are made of cable that move continuously and sleds get attached to moving tracks. In this embodiment, the track is cable  66  which is being pulled by pulley  61  in the direction of  69  which is powered by a prime mover inside base  68 . The pulley  61  is movable up and down along the axis of rotation shown as  65 . The actuator inside base  68  aligns pulley  61  with the desired pulley which may be  62 ,  63  or  64 . Once the pulleys are aligned, the sled coming from the incoming track  66  is transferred to outgoing track  67 . In this embodiment the sled has no prime mover inside and simply gets attached to the moving cable assembly to tow the attached vessel. The sled gets clamped to the cable  66  and approach the switch assembly from the direction of  69 . Incoming sled  77  is guided by pulley  61  which is aligned with one of the output tracks guided by pulleys  62 ,  63  or  64 . In the figure pulley  61  is aligned with pulley  62 , so the coming sled  77  gets transferred to track  67 .  FIG. 8B  shows the sled for this particular embodiment of the design. The sled has two clamping parts  71  and  73  connected by a semi rigid part  72 . When sled gets attached to track which is in the form of cable, both clamps  71  and  73  are activated and they clamp to the cable. As the sled moves through the switch  73  releases the cable  66  while  71  is still clamping to cable  66 . When sled is sufficiently advanced through the switch, the clamp  73  clamps the cable  67  and clamp  71  releases cable  66 . 
       FIG. 9  shows yet another embodiment of the system where tracks appear as chains.  FIG. 9A  shows the track and the sled system where the chain  71  works as the track for the system and moved by gear  72 . The sled assembly is shown as  74  and has two clamping parts  75  and  76 . Rear clamp  75  and front clamp  76  are connected through semi rigid connecting part  78  which can bend and comply as it moves along the tracks.  FIG. 9B  shows the mechanism of alignment for this embodiment of the switch. Gear  72  is free to move vertically along the direction of  86  and gets aligned with one of the outgoing tracks  79 ,  77  or  80 . The sled gets clamped to moving chain by using special tooth on the sled.  FIG. 9C  and  FIG. 9D  show the details of the clamp mechanism.  FIG. 9C  shows the clamped version of the sled where the distance between tooth  81  and  82  is enlarged and unit gets engaged with the chain.  FIG. 9D  shows the released version of the embodiment where the distance between tooth  81  and  82  is reduced and assembly gets detached from the chain. 
       FIG. 10  shows an environmentally friendly embodiment of the invention where a streamlined cargo container is towed under the water surface without being affected by the weather elements or the wave conditions. An unmanned cargo container  92  is towed right below the water line  90  by the sled arrangement of the invention. The system may be powered by wind turbines  91  erected along the path of the tracks.