Abstract:
The present invention discloses an escort vessel towline force responsive apparatus comprising a rotative winch system mounted to the deck of an escort vessel so that when the tow line between a distressed vessel and the winch system of an escort vessel angularly changes, the escort vessel winch system will automatically rotate until the line of force is substantially in linear alignment with the center line of the escort vessel winch system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to winch systems and, more specifically, to a staple-torque rotative winch mounted to the deck of an escort vessel so that when an escort vessel tow line extends from the winch drum through a staple or bullnose to an escorted vessel, the staple serves as towline guideway so that lateral tow line torque forces impinged on the staple rotates the winch so that the towline is substantially in linear alignment with the center line of the escort vessel winch system and the escorted vessel tow anchor point. 
     2. Description of the Prior Art 
     There are other winch systems designed for escort tugs. While these systems may be suitable for the purposes for which they where designed, they would not be as suitable for the purposes of the present invention as heretofore described. 
     It is thus desirable to provide an escort tug with a deck mounted rotative winch so that when the winch rotates towards the line of force the heel angle of the tug decreases. 
     SUMMARY OF THE PRESENT INVENTION 
     A primary object of the present invention is to provide an automatically rotative winch system for an escort vessel tow line. 
     Another object of the present invention is to provide an escort vessel winch system that reduces the side force on the winch. 
     Yet another object of the present invention is to provide an escort vessel with a winch system that is deck mounted on a slewing ring. 
     Still yet another object of the present invention is to provide an escort vessel with a rotative winch system that is capable of reducing the heeling angle of an escort vessel without reducing the line pull. 
     Another object of the present invention is to provide an escort vessel with a rotative winch system that is capable of increasing line pull as the heeling angle of the escort vessel increases. 
     Additional objects of the present invention will appear as the description proceeds. 
     The present invention overcomes the shortcomings of the prior art by providing an automatically rotative winch mounted to the deck of an escort vessel so that when the tow line force between a distressed vessel and the winch system of an escort vessel angularly changes, the escort vessel winch system will automatically rotate until the line of force is substantially in linear alignment with the center line of the escort vessel winch system. 
     The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawings, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawings, like reference characters designate the same or similar parts throughout the several views. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       In order that the invention may be more fully understood, it will now be described, by way of example, with reference to the accompanying drawing in which: 
         FIG. 1  is an illustrative view of the present invention in use. 
         FIG. 2  is a side view of the present invention. 
         FIG. 3  is a side view of the present invention. 
         FIG. 4  is a view of method of the present invention. 
         FIG. 5  is a chart showing maximum steering test data results for forward ship speeds of 8 and 10 knots for the escort tug using conventional staple. 
         FIG. 6  is a chart showing maximum steering test data results for forward ship speeds of 8 and 10 knots for the escort tug using the torque rotative winch of the present invention. 
         FIG. 7  is a chart showing maximum braking test data results for forward ship speeds of 8 and 10 knots for the escort tug using conventional staple. 
         FIG. 8  is a chart showing maximum braking test data results for forward ship speeds of 8 and 10 knots for the escort tug using the torque rotative winch of the present invention. 
         FIG. 9  is a side view of the winch of the present invention. 
         FIG. 10  is a top view of the winch of the present invention. 
         FIG. 11  is a top view of the winch of the present invention. 
         FIG. 12  is a top view of the winch of the present invention. 
         FIG. 13  is a view of the winch anti-trip bearing of the present invention. 
     
    
    
     DESCRIPTION OF THE REFERENCED NUMERALS 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the Figures illustrate the method of constructing a catalog of the resources accessible through a network of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures.
           10  force responsive towline apparatus of the Present Invention     12  winch     14  slewing ring     16  distressed vessel     18  escort vessel     20  line     22  propulsion force     24  center of pressure (COP)     26  beam     28  distance between propulsion unit and beam     30  distance between COP and beam     32  inner race     34  anti slip bearing     36  conventional staple     38  auto position winch     40  speed—knots     42  max. steering force     46  associated braking force     48  tug angle to flow     50  towline angle to ship     50  towline angle to tug     52  heel angle     54  residual freeboard       

     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following discussion describes in detail one embodiment of the invention. This discussion should not be construed, however, as limiting the invention to those particular embodiments, practitioners skilled in the art will recognize numerous other embodiments as well. For definition of the complete scope of the invention, the reader is directed to appended claims. 
     Referring to  FIG. 1 , shown is an illustrative view of the present invention in use. The winch system  10  of the present invention was designed for the purpose of increasing the line pull (steering force) and safety of tugs  18  escorting ships  16  in protective waters using a simple mechanical advantage. An escort tug  18  is defined as a tug tethered  20  to the stern of a large ship or tanker  16 . In an emergency, if a tanker or ship  16  has a loss of power or rudder failure the escort tug  18  will be ordered to go to the port or starboard side of the tanker (line or hawser  20  is attached to the ship or tanker) and will be directed by the pilot to go into the indirect mode or power indirect mode. The indirect mode is defined as an escort tug at 45 degrees to the tanker and at a jackknifed position with the z drives (thrusters) facing towards the ship the forces of dragging the tug through the water will control or turn the ship or tanker. The indirect mode can be used and is effective at higher speeds but is harder to get into position. 
     The present invention provides a winch system  10  that turns toward the line of force when said force is applied to the winch&#39;s integral staple whereby the heel angle will be reduced for the same line pull. 
     Referring to  FIG. 2 , shown is a side view of the present invention. As shown in the illustration, for the tug  18  to be in equilibrium the equation P×X=COP×Y and P+T=COP (“P” is “Z” drive force  22 , “T” is tow line force  26  and “COP” is the tugs center of pressure  24  (the convergent point between the thruster forces and the winch towline force) must be achieved. If you isolate the terms T=COP×(1−Y/X) is reduced the tow line  20  pull “T” will increase. As the winch of the present invention  10  rotates and “Y” becomes closer to the “COP” the ratio of “X” to “Y”  28 ,  30  is reduced and the line pull will increase with the same force at “P”. 
     Referring to  FIG. 3 , shown is a side view of the present invention. The winch system of the present invention  10  and staple  26  (tow point) rotates 32 on a large slewing ring  14  and reduces the side loading on the escort vessel  18  winch also producing a level toe line wind. 
     Referring to  FIG. 4 , shown is a view of the method of the present invention. As the winch system of the escort vessel  14  turns  26  toward the line of force  20  the moment is decreased and the heel angle of the escort vessel  14  is reduced for the same line pull. The winch rotates at a right angle to the tug, the line pull will remain the same with less of a heeling angle or as the heeling angle is increased the line pull will also increase. Conceptual calculations indicate the winch system will increase tow line force by 25% and reduce a tug&#39;s heel angle by as much as 40%, which was born out by model testing using a 39 VSP tractor tug. 
     Referring to  FIGS. 5 and 6 , shown is escort tug maximum steering test data results for forward ship speeds of 8 and 10 knots for the escort tug using conventional staple and the auto position winch. The data shows the sign convention in which the forces and angles are presented. 
     Forward ship speed  40  of 8 knots using an escort tug with conventional staple showed a steering force  42  of 81 tonnes; associated braking force  44  of −9 tonnes; tug angle to flow  46  of −143°, towline angle to ship  48  of 84°; towline angle to tug  50  of −59°; heel angle  52  of 9.4 degrees and a residual freeboard  54  of 0.01 m. The data for the escort vessel equipped with the auto position winch ( FIG. 6 ) produced a steering force  42  of 89 tonnes and braking force  44  of −14 tonnes. A 10% increase in steering force and increased braking force of &gt;50%. Decreases in tug angle to flow  46 , towline angles  48 ,  50 , heel angle  52  and increase in residual freeboard  54  shows the increased capabilities of an escort tug having the auto position winch of the present invention. Also shown in  FIGS. 5 and 6  are the test data results for a forward ship speed of 10 knots using an escort tug with conventional staple and the auto position winch again showing the increased capabilities of employing the auto position winch of the present invention. 
     Referring to  FIGS. 7 and 8 , shown is escort tug maximum braking test data results for forward ship speeds of 8 and 10 knots for the escort tug using conventional staple and the auto position winch. The data shows the sign convention in which the forces and angles are presented. 
     Forward ship speed  40  of 8 knots using an escort tug with conventional staple showed a steering force  42  of 101 tonnes; associated braking force  44  of 0 tonnes; tug angle to flow  46  of 180°; towline angle to ship  48  of 0°, towline angle to tug  50  of 180°: heel angle  52  of 0° and a residual freeboard  54  of 1.68 m. The data for the escort vessel equipped with the auto position winch ( FIG. 8 ) produced a steering force of 101 tonnes and braking force of 0 tonnes; tug angle to flow  46  of 180°, towline angle to ship  48  of 0°, towline angle to tug  50  of 180°: heel angle  52  of 0° and a residual freeboard  54  of 1.68 m. Also shown in  FIGS. 7 and 8  are the test data results for a forward ship speed of 10 knots using an escort tug with conventional staple and the auto position winch. Again showing the increased capabilities of employing the auto position winch of the present invention. 
     Referring to  FIG. 9 , shown is a side view of the winch of the present invention. The winch system  12  and staple  26  (tow point) of the present invention  10  rotates via  32  on a large slewing ring  14  and reduces the side loading on the winch and also produces a level wind. As the winch system of the present invention turns toward the line of force the movement is decreased and the heel angle reduced for the same line pull. The winch rotates at a right angle to the tug, the line pull will remain the same with less of a heeling angle or as the heeling angle is increased the line pull will also increase. 
     Referring to  FIG. 10 , shown is a top view of the winch of the present invention. The winch system  12  and staple  26  (tow point) of the present invention rotates on a large slewing ring  14  and reduces the side loading on the winch producing a tow line level wind. 
     Referring to  FIGS. 11 and 12 , shown are top plan views of the winch system of the present invention  10 .  FIG. 11  illustrates the winch  12  and staple  26  in a forward position having inner race  32  and slewing ring  14  providing automatic rotation dependant on the line of force. The force responsive tow line apparatus  10  is mounted to travel at a right angle to the escort vessel deck thereby as the line of force between the escort vessel and distressed vessel angularly deviates from the center line of winch  12  and staple  26 , winch system  10  automatically rotates until the line of force linearly aligns with the center line of winch system  10 , as illustrated in  FIG. 12 . 
     Referring to  FIG. 13 , shown is a view of the winch anti-trip bearing of the present invention. Illustrated is inner race  32  and outer race  14  having anti-trip bearing  34  positioned thereon. 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of devices differing from the type described above. 
     While certain novel features of this invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.