Abstract:
Deployment of a moored undersea device is achieved by fixing a mooring line to an anchor, and allowing the mooring line to unwind from a winding reel. A winding reel control mechanism is responsive to underwater hydrostatic pressure to release the mooring line when the hydrostatic pressure exceeds a predetermined level. When the hydrostatic pressure falls below the predetermined level, the winding reel control mechanism prevents further pay out of the mooring line.

Description:
BACKGROUND 
     This disclosure describes a device and technique to automatically moor an object, which has been released from the bottom of the ocean, at a predetermined distance below the surface of the water. 
     SUMMARY 
     Apparatus for deployment of a moored undersea device includes an anchor, a mooring line attached to the anchor and a winding reel. The winding reel is provided with a mooring line engagement mechanism which controls unwinding of the mooring line. The mooring line engagement mechanism responds to underwater hydrostatic pressure to engage the mooring line when hydrostatic pressure falls below a predetermined level. A buoyancy mechanism is used and is capable of buoying an assembly which comprises the winding reel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a diagram showing an example configuration of a mooring line brake. 
         FIG. 2  is a diagram showing an example of a different configuration of a mooring line brake. 
         FIG. 3  is a diagram showing details of a latch mechanism as may be used in the configuration of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     In certain mooring applications, it is desired to anchor a mooring device and cause the mooring device to extend to a certain moored height. The moored height is thus a predetermined depth below the surface of the water. The moored height is a predetermined depth which is established from the surface (hence “depth”), as opposed to defining the moored height as a measurement from the anchor point. Consequently, the length of the mooring line is a function of the predetermined depth, the distance from the predetermined depth to the sea bottom anchor point and the current. 
     Previous methods to moor objects included a line of predetermined length and other electronic braking devices; however, a mooring line of predetermined length only works to achieve the predetermined depth if the exact water depth and the exact current are known beforehand. The determination of water depth requires that a precise determination of the anchor point be made. The determination of current requires a determination of water depth and the strength of the currents at different depths. It is also necessary to integrate the effects of current along the mooring line, thereby factoring in the force of current on the moored object. It would be desirable to be able to moor objects at a predetermined depth without the need for a precise calculation of depth to the anchor point and/or without a need to precisely integrate current along the mooring line, factored in with the force of current on the moored object. 
     Electronic mooring line braking devices are relatively complex, require electrical power to operate, and require larger forces to pay out the mooring line. 
     The disclosed technique allows objects to be moored at desired depths without a need to pre-calculate the current or water depth. 
     The disclosed apparatus comprises a spool on which is wound a mooring line, a spring, an o-ring, a pin and a cone. This device has a pin sealed by using an o-ring that has atmospheric pressure on one side and hydrostatic pressure on the other. The spring is locked on the atmosphere side resisting the hydrostatic pressure. At depth, the hydrostatic pressure overcomes the spring force and pushes the pin in. As the device ascends in the water column, the decreasing hydrostatic pressure allows the spring force to overcome the depth pressure activating the pin, which in turn catches or trips the mooring line. The pin thereby blocks movement of the mooring line from unwinding about the spool, which prevents further payout from the spool. By varying spring properties, pin dimension, o-rings and o-ring grooves, the depth at which the brake activates can be tuned for the specific brake application. 
     This design provides for a simple operation requiring no external power or electronics to activate the brake. Because of this simplicity, this design has advantages of smaller size and lower mooring line pay out tensions. 
     Spooled Mooring Line with Payout Cone and Locking Pin 
       FIG. 1  is a diagram showing an example configuration of a mooring line brake  101 . Depicted are mooring line spool  111 , mooring line payout cone  113  and locking pin  115 . Locking pin  115  includes piston  117  and engagement extension  119 . The components are either buoyant or external buoyancy may be attached. In the case of external buoyancy, the external buoyancy is added by attachment to a fitment, as represented by attachment ring  120 , and therefore the fitment becomes a means for providing the external buoyancy. 
     O-ring  125  forms a seal for piston  117  and spring  129  acts against piston  117 . Piston  117  and spring  129  are received in chamber  131  within spool  111 . Chamber  131  extends from a payout flange  135  of spool  111  and extends radially toward the center of spool  111 . Chamber  131  is set at a predetermined gas pressure, such as atmospheric pressure. Piston  117  has an exterior side which forms engagement extension  119 . The exterior side or engagement extension  119  is exposed to ambient pressure which is atmospheric pressure during non-deployment storage, but which is hydrostatic pressure when deployed in a sea environment. The action of piston  117  in chamber  131  is similar to that of a pressure regulator valve, in that piston  117  responds to a combination of the balance of pressures and the biasing of spring  129 . The sea&#39;s hydrostatic pressure urges piston  117  inward against the atmospheric pressure in the chamber; however piston  117  must also overcome the force of spring  129 , so that piston  117  remains in a position toward an outer perimeter of payout flange  135  until the hydrostatic pressure is sufficient to overcome the force of spring  129 . 
     Piston  117 , chamber  131  and spring  129  are sized to cause engagement extension  119  to extend beyond the spool&#39;s outer perimeter at payout flange  135  when the sea&#39;s hydrostatic pressure is not sufficient to force piston  117  inward. Spring  129  is chosen to set the hydrostatic pressure at which piston  117  retracts. This hydrostatic pressure determines the predetermined depth at which mooring line brake  101  actuates to prevent further line payout. 
     Mooring line payout cone  113  fits over mooring line spool  111  and acts as a feed guide. Mooring line  141  is wound around spool  111  and has a free end  141 A extending outward from mooring line spool  111  past payout flange  135 . Free end  141 A could be attached to a sea bottom positioned anchor  141 B, for example. With locking pin  115  retracted into spool  111 , the mooring line  141  is free to unwind from spool  111 . When the mooring line  141  pays out, free end  141 A must wind about payout flange  135  and pass locking pin  115  on each winding rotation. As a result, when piston  117  extends outward to allow extension  119  to extend beyond the outer diametrical perimeter of payout flange  135 , extension  119  will engage payout cone  113 , thereby blocking and arresting the free end  141 A of the mooring line  141  from further payout. Since this condition occurs at and above the predetermined depth and does not exist below the predetermined depth, mooring line  141  is free to unwind below the predetermined depth, but piston  117  and extension  119  restrain such unwinding above the predetermined depth. 
     Mooring line  141  is allowed to payout by rotation with respect to payout cone  113  to the point of reaching the predetermined depth, and will take into account the effect of sea currents on mooring line  141 . This would work in a static situation, meaning fixed depth of anchorage and fixed currents. Tidal variations can change depth, and it is possible that changes in the depth of the mooring line brake  101  will occur in response to daily tides. Sea currents also change as a result of tides, weather conditions or from transient events such as movement of a ship past the mooring. These changes could periodically cause the mooring line brake  101  to sink below the predetermined depth. If, during such transient events, the mooring line brake 101  payed out additional mooring line  141 , then the mooring line brake  101  would rise above the predetermined level over time. 
     To prevent the mooring line brake  101  from paying out more line during transient events, it is possible to include a bleed valve  147  placed in communication with chamber  131 . Bleed valve  147  may optionally be plugged with a sea water soluable material (not separately shown) to delay the bleed function. Bleed valve  147  permits water at hydrostatic pressure to slowly leak into chamber  131 , gradually allowing the pressure inside chamber  131  to rise to that of hydrostatic pressure at the predetermined depth. As a result, transient changes in depth resulting from tidal variations and current variations will no longer be sufficient to cause piston  117  to retract inward by overcoming spring pressure (spring  129 ). Consequently, mooring brake  101  can retain the mooring line  141  at a fixed length. 
     Example 
     Spooled Mooring Line with Flap Catch 
       FIG. 2  is a diagram showing an example of a different configuration, mooring line brake  201 , in which a catch flap  205  functions as a latch piece to arrest line movement. As is the case of the configuration of  FIG. 1 , the arrangement similarly uses a line spool  211  and a mooring line payout cone  213 . A locking piston  217  is provided, but is used to engage catch flap  205 , details of which are depicted in  FIG. 3 . As is the case with the configuration of  FIG. 1 , the components of the configuration of  FIGS. 2 and 3  are either buoyant or an external buoyancy mechanism is attached, as may be effectuated via attachment ring  220 . 
     O-ring  225  forms a seal for piston  217  and spring  229  acts against piston  217 . Piston  217  and spring  229  are received in chamber  231  within spool  211 . Chamber  231  is otherwise sealed, as represented by plug  233 . Chamber  231  extends from a pay out flange  235  of spool  211  and extends radially with respect to spool  211 . Chamber  231  is set at a predetermined gas pressure, such as atmospheric pressure. The exterior side of piston  217  is exposed to ambient pressure which is also atmospheric pressure during non-deployment storage, but which is hydrostatic pressure when deployed in a sea environment. The action of piston  217  in chamber  231  is similar to that of a pressure regulator valve, in that piston  217  responds to a combination of the balance of pressures and the biasing of spring  229 . The sea&#39;s hydrostatic pressure urges piston  217  inward against the atmospheric pressure in the chamber; however the hydrostatic pressure against piston  217  must also overcome the force of spring  229 , so that piston  217  remains in a position toward an outer diametrical perimeter of payout flange  235  until hydrostatic pressure is sufficient to overcome the force of spring  229 . 
     Piston  217 , chamber  231  and spring  229  are sized to cause locking piston  217  to extend beyond the spool&#39;s outer perimeter at payout flange  235  when the hydrostatic pressure is not sufficient to force piston  217  inward. Spring  229  is chosen to set the hydrostatic pressure at which piston  217  retracts. This hydrostatic pressure determines the predetermined depth at which the mooring line brake  201  actuates to prevent and arrest further line payout. 
     Mooring line payout cone  213  fits over mooring line spool  211 . As is the case with the configuration of  FIG. 1 , mooring line  141  is wound around spool  211  and has a free end  141 A extending outward from mooring line spool  211  past pay out flange  235  and to anchor  141 B. With locking piston  217  refracted into spool  211 , the mooring line  141  is free to unwind from spool  211 . When the mooring line  141  pays out, free end  141 A must wind about pay out flange  235  and pass locking piston  217  on each winding rotation. As a result, when piston  217  extends outward to allow locking piston  217  to extend beyond the diametrical outer perimeter of payout flange  235 , locking piston  217  will engage catch flap  205 , which acts as a latch piece. Catch flap  205 , in turn, arrests the mooring line  141 , which prevents further payout of the mooring line  141 . Piston  217  therefore engages catch flap  205  so as to open catch flap  205 . 
     With the mooring line  141  is engaged by catch flap  205 , catch flap  205  is prevented from retracting. Thus, when the depth of mooring line brake  201  increases, mooring line  141  remains engaged by catch flap  205 . When the depth of mooring line decreases, locking piston  217  again engages catch flap  205  and mooring line remains engaged by catch flap under this condition as well. During engagement by the latch piece of the mooring line, the mooring line retains the catch flap  205  in the engagement position. The retention of the mooring line by the catch flap  205  prevents disengagement of the mooring line until release of tension of the mooring line. 
       FIG. 3  shows details of catch flap  205 . Catch flap  205  is hinged in substantial parallel alignment to the free end  141 A of the mooring line  141 . If mooring line  141  is wound around spool  211  to unwind past catch flap  205  from hinge end  241  toward free end  242 , then mooring line  141  will be seized by groove  235 . If mooring line  141  is wound so that unwinding causes the free end  141 A to pass catch flap  205  from hinge end  241  to the free end  242 , then mooring line  141  can force piston  217  inward, given enough force between attachment ring  220  and free end  141 A. 
     As depicted in  FIG. 3 , catch flap  205  is formed with a groove  235  designed to conform to part of the exterior of mooring line  141 . Groove  235  catches mooring line  141  and reduces the ability of the mooring line to apply pressure to the piston mechanism by reducing the rotational vector of force applied by the free end of the mooring line  141 A to catch flap  205 . As a result, during engagement by the latch piece of the mooring line, the mooring line at least partially engages a portion of the latch piece by catching on groove  235 . This prevents the mooring line from resetting the mooring line brake  201  until the force applied by mooring line  141  establishes a rotational vector about the hinge sufficient to close catch flap  205  against piston  217  and spring  229 . Groove  235  is configured so that, during engagement by the catch flap  205  of mooring line  141 , the catch flap  205  reduces or eliminates force applied to the disengage piston  217  and spring  229 . This reduces a tendency of catch flap  205  to disengage mooring line  141  and, in turn, accommodates tidal variations and other changes in depth after deployment of the mooring line brake  201 . 
     It is possible to configure groove  235  so that force applied by mooring line  141  to groove  235  acts to prevent catch flap  205  from releasing mooring line  141 . 
     It is alternatively possible to wind mooring line  141  so that free end  141 A passes catch flap  205  from free end  242  to hinge end  241 . This permits mooring line  141  to snag catch flap  205  to the locked position. In that circumstance, once mooring line  141  is blocked by catch flap  205 , it becomes difficult to free mooring line  141  to extend further. 
     Variations 
     The above descriptions are of configurations which demonstrate example implementations of the disclosed concepts. It is possible to implement the latch mechanism by the use of different pin shapes to help catch the mooring line, different size springs, different o-ring and different pins. Additionally, the brake can operate on different components, such as, for example, preventing rotation of a rotating spool. 
     It is also possible to provide the piston or catch flap on the outer cone or cover, so that the piston or catch flap engages toward the spool. This would further allow the piston or catch flap to block the mooring line by extending past a flange portion of the spool. 
     Conclusion  
     It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated to explain the nature of the invention, may be made by those skilled in the art within the scope of the invention as expressed in the appended claims.