Abstract:
A cable brake system for deployments of cable comprising: a frame configured to be mounted on a ship; a repeater supporting track mounted longitudinally to the frame, the supporting track being configured for slidingly supporting a plurality of repeaters; a spool positioned exterior to the frame, the spool having the cable wrapped therearound and being capable of supplying the cable to an interior of the frame; at least one planar surface on an interior of the frame, the planar surface being positioned approximately parallel to the repeater supporting track; and a plurality of brake sub-assemblies being supported by the planar surface in a manner so as to establish a serpentine path for the cable and to impart variable frictional resistance to the cable.

Description:
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT 
     This invention (Navy Case No. 96,881) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Space and Naval Warfare Systems Center, San Diego, Code 2112, San Diego, Calif., 92152; voice 619-553-2778; email T2@spawar.navy.mil. 
    
    
     BACKGROUND 
     There are several challenges associated with the deployment of fiber-optic cable in water. To prevent wasteful, unrestrained payout of the cable, especially in deep water, tension is typically applied to the cable by way of capstans or hand tension. These previous techniques have draw-backs, however, such as cable damage in the event of a cable snag, limited sequential in-line sensor deployment capability, and lack of precision/control. A need exists for a system with improved functional capability and greater control of optical-cable deployment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  shows a schematic of a ship equipped with the presently disclosed system. 
         FIG. 1   b  shows a side view of a cable brake system. 
         FIG. 2  shows an actuator/brake-hub sub-assembly. 
         FIG. 3  shows a perspective view of a sensor assembly. 
         FIG. 4  shows a sensor for counting revolutions of a drum; and 
         FIG. 5  shows perspective view of a cable brake system. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1   a  and  1   b  show a cable brake system  10  for deployments of light cable  12 , e.g. fiber optic cable, into water. The cable brake system  10  has the ability to control and monitor the tension, deployment speed, and the amount/length of cable  12  that has been deployed off of a ship  14 . The cable brake system  10  comprises a plurality of brake sub-assemblies  16 , and a sensor assembly  18 . The brake sub-assemblies  16  and the sensor assembly  18  are mounted to a frame  20 , which may be mounted to the deck of the ship  14 . The brake sub-assemblies  16  may be positioned on the frame  20  to produce a serpentine cable path when activated. Both the braking force and the position of the brake sub-assemblies  16  are adjustable so that the amount of tension on the cable  12  may be regulated to correspond with the depth of the water, the speed of the ship  14  and the amount of slack desired. Although  FIG. 1   b  shows the brake sub-assemblies  16  as comprising three brake sub-assemblies, it is to be understood that the brake sub-assemblies  16  may comprise any number of brake sub-assemblies that is greater than or equal to two. As shown in  FIG. 1   b , the sensor assembly  18  is positioned on the frame  20  aft of the brake sub-assemblies  16 . 
     The cable  12  may be stored in cable packs  22  and on a larger spool  24 . Cable packs  22  may be formed by winding cable  12  within a binder material (e.g. glue) that, when cured, holds the cable  12  in-place within the cable packs  22 . Several wraps of the cable  12  are also wound on to the spool  24 , which has an internal spool brake  26  (shown in a cutaway section of the spool  24  in  FIG. 1   b ) (i.e. rotational speed of the spool  24  can be slowed by its own the spool brake  26 ). The spool  24  can also be equipped with a spool rotation sensor  28  that serves as an approximate measure of the length of cable that has passed out of the spool  24 . The combined use of the spool  24  and the cable packs  22  on the cable brake system  10  allows for both pay-out of cable  12  and for in-line sensors  30  (fiber optic signal repeaters or similar) to be smoothly deployed. Over-boarding guides  32  may be mounted to the frame  20  to guide the cable  12  and the in-line sensors  30  as they are deployed off the ship  14 . The over-boarding guides  32  have a gradual negative slope to drop the in-line sensors  30  overboard as necessary. Deployment of the in-line sensors  30  may be electronically initiated via an in-line sensor release mechanism  33  and may be governed by a drive to achieve smooth deployment. One embodiment of the spool rotational sensor  28  utilizes a light source  35  and a reflective surface  37  on a side of the spool  24  such that each time the reflective surface passes the spool rotational sensor  28  senses the reflected light from the reflective surface. It is to be understood that the spool rotational sensor  28  may be any sensor capable of sensing the rotation of the spool  24 . 
     The frame  20  can be constructed of structural members necessary to support cable packs  22 , in-line sensors  30 , brake sub-assemblies  16 , and the over-boarding guides  32 . Space frame construction of the frame  20  may be employed to lower the weight of the cable brake system  10 , while allowing ample load-bearing capacity and mounting options for the mechanical interface to the ship  14 &#39;s deck. Each element of the cable brake system  10  may be constructed using components that resist corrosion in a marine environment. Cable rollers  34  may be positioned at the aft end of the over-boarding guides  32  (as shown in  FIG. 1   b ) and between the brake sub-assemblies  16  (as shown in  FIG. 5 ). 
       FIG. 2  shows an embodiment of an individual brake sub-assembly  16 . Each brake sub-assembly  16  includes an actuator  36  mechanically coupled to a brake shaft  38 , which is keyed to a brake hub  40 . The brake hub  40  has an outer covering  42  that has a high coefficient of friction, such as rubber, to grip the cable  12  more effectively. The actuator  36  may be any type of actuator capable of moving the brake sub-assembly  16  with respect to the frame  20 , such as hydraulic, electrical, and/or mechanical actuators. Each actuator  36  is configured to move its corresponding brake sub-assembly  16  along a track (not shown) that is connected to the frame  20  through stabilizing bars  44 . The actuator  36  repositions the brake shaft  38  with respect to the brake shafts  38  of other brake sub-assemblies  16  as necessary, i.e., the actuator  36  brings the brake shaft  38  closer to or pushes it farther from another brake shaft  38 . The brake sub-assemblies  16  are positioned such that; when activated, each brake sub-assembly  16  is positioned, in series, along a centerline and the cable  12  moves in a serpentine path around the brake hubs  40 . The serpentine path created by the cable  12  may be seen in  FIG. 5 . When de-activated, the brake hubs  40  move outward, alternately on one side or the other of the centerline cable-path, and the cable  12  passes freely through the straight-line path without experiencing braking action. When activated, the brake sub-assemblies  16  produce tension in the cable  12  during deployment. In the limit, the brake sub-assemblies  16  can also be used to hold the cable  12  steady, without any deployment. In addition, each of the brake sub-assemblies  16  comprises a brake rotor  46  and a caliper  48 , which provide the braking force. During operation, any single brake sub-assembly  16  can impart resistance to cable  12  payout; up to the point that the cable  12  starts slipping on the outer covering  42 . 
     At specified intervals during a cable deployment, an in-line sensor  30  can be deployed by momentarily opening the serpentine brake arrangement, previously described, and passing the in-line sensor  30 . Once the in-line sensor  30  has passed, the serpentine cable-path is re-established and braking is activated again. This is accomplished by a control system, which commands the actuators  36 , which move the brake sub-assemblies  16 . In one example embodiment, the in-line sensor may be a cylindrical repeater/amplifier with an approximate 20-inch diameter. It is to be understood that the in-line sensor  30  is not limited to cylinders, but may be any size or shape. The in-line sensor  30  can be deployed in-line/mid-span of the cable  12  being deployed by temporarily deactivating the brake sub-assemblies  16  and allowing the in-line sensor  30  to be deployed through the over-boarding guides  32 . This function may be accomplished by a processor  62 , described below. 
       FIG. 3  shows an embodiment of the sensor assembly  18 . The sensor assembly  18  comprises a sensor hub  50  that is keyed to a sensor shaft  52 . The sensor shaft  52  is coupled to a sensor actuator  54  that is configured to slide the sensor assembly  18  on trolleys  56  to and fro along a track (not shown) that is mounted to the frame  20 . The sensor assembly  18  also comprises a force transducer  58 , such as a tensometer, and a hub rotation sensor  60 . The force transducer  58  may be used to measure a tension value of the cable  12 . The hub rotation sensor  60  may be used for measuring rotations per minute of the sensor hub  50  and, as a result, for measuring the deployment speed of cable  12 . When the sensor hub  50  is allowed to rotate freely the sensor assembly  18  can determine the amount of tensile force on the cable  12  by pressure applied by the cable  12  against the sensor hub  50 . 
       FIG. 4  is a diagram showing the relationships between the previously described elements of the cable brake system  10  and a processor  62 . The processor  62  may be configured to receive sensor hub rotational information from the hub rotation sensor  60 , tension information from the force transducer  58 , and spool rotation information from the spool rotation sensor  28 . The processor  62  may be configured to control the spool brake  26 , the brake actuators  36 , the brake calipers  48 , the sensor actuator  54 , and the in-line sensor release mechanism  33 . The processor  62  may be used to determine tension, speed and deployed-length of the cable  12 . The deployed-length and payout speed may be calculated directly using the rotational velocity data from the hub rotation sensor  60 , together with a running clock in the processor  62 , and the known constants associated with the sensor hub  50  geometry (one hub revolution equals one hub perimeter of cable that has been deployed). The hub rotation sensor  60  counts the number of rotations per specific period of time of the sensor hub  50 . 
     The processor  62  conducts data acquisition and is also capable of applying deployment logic to make braking decisions. The processor  62  can be programmed to modulate the braking force at any or all of the brake sub-assemblies  16  by controlling the brake calipers  48  on the brake rotors  46 . Additionally, the processor  62  can also activate or deactivate the brake system  10  by controlling the actuators  36  and the sensor actuator  54 . With comprehensive programming (software), the processor  62  could manage the entire test sequence for a cable deployment mission. Lab-view™ software is a suitable example of software that may be used with the processor  62  to perform the above-described operations. The brake system  10  can automatically provide more tension during payout in deeper water (where a run-away deployment condition could occur if the cable  12  is not restrained) and less tension in shallow water (where there is a lower likelihood of the run-away condition). Upper limit thresholds for tension could also be set to avoid cable damage if the cable  12  was inadvertently snagged or pulled during the deployment. 
       FIG. 5  shows a perspective view of one embodiment of the cable brake system  10 . In the embodiment shown in  FIG. 5 , the brake sub-assemblies  16  are provided on a horizontal planar surface  64  of the cable brake system  10 . The horizontal surface  64  has tracks  66  along which the brake sub-assemblies  16  and the sensor assembly  18  can slide. When the processor  62  determines that the cable  12  is being deployed too fast or too slow, the processor  62  signals the actuator  36  of each of the brake sub-assemblies  16  to move their corresponding brake shafts  38  toward or away from the cable  12  thereby, respectively applying more or less pressure on the cable  12  by the brake hubs  40 . For storage and deployment of in-line sensors  30 , a deployment track  68  may be mounted to the frame  20 . The in-line sensors  30  may be configured to slide along the deployment track  68  once released by the in-line sensor release mechanism  33 . 
     The previous description of the disclosed functions is provided to enable any person skilled in the development process for a similar concept to make or use the present inventive subject matter. Various modifications to these functions will be readily apparent and the generic principles defined herein may be applied to additional functions without departing from the spirit or scope of the inventive subject matter. For example, one or more of the brake system functions can be rearranged and/or combined, or additional functional elements may be added. Thus, the present inventive subject matter is not intended to be limited to the set of functions shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
     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 principal and scope of the invention as expressed in the appended claims.