Abstract:
A surface floating buoy has an antenna attached to a linkage system which pivots about the floating buoy. The linkage system is attached to a counterweight such that the antenna is maintained at a desired vertical position with respect to the surface of a body of water by pantographic action. The floating buoy contains a hollow cavity of sufficient size to hold the linkage system antenna and counterweight prior to deployment in a body of water. Upon deployment in the water, gravitational forces on the counterweight and linkage system cause the system to be deployed. The invention may also include a servo feedback system for more accurately positioning the antenna at its desired position.

Description:
FIELD OF THE INVENTION 
     This invention relates to sonobuoys, and more particularly to an antenna stabilizing deployable mast system for a surface floating buoy. 
     BACKGROUND OF THE INVENTION 
     Surface floating buoys have been used as platforms to support antennas and a variety of other sensors, e.g. optical devices, magnetic sensors, etc. The heave response of such a buoy serves to maintain the sensor above the surface of the water. Heretofore, antennas have been directly attached to the body of the buoy. As a result, the antennas have tended to bobble and roll with the buoy due to the action of waves and wind. This angular displacement can severely degrade antenna directivity performance objectives. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a deployable mast of sufficient height for a sensor to view over ocean waves and at the same time provide the sensor with isolation to angular displacement by wind and waves. 
     It is another object of the present invention to provide a deployable mast having linkage of a type that can be folded and packaged completely within the main body of a hollow buoy. 
     The present invention accomplishes these objectives by providing a sonobuoy with both heave response and vertical stability. This is accomplished, in brief, by attaching the sensor to an element of a linkage system which pivots about a surface floating buoy. A counterweight is attached to an additional element of the linkage system such that the sensor is maintained at a desired vertical orientation by pantographic action. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention will be readily obtained by reference to the following description of the Preferred Embodiments and the accompanying drawings in which like numerals in different figures represent the same structures or elements wherein: 
     FIG. 1 illustrates a single four-bar linkage system with preloaded torsion hairpin springs where the linkage element attached to the antenna remains vertical irrespective of the displacement of the flotation element. 
     FIG. 1A illustrates in greater detail one of the joints and its preloaded torsion hairpin spring as used in FIG. 1. 
     FIG. 2 illustrates a single four-bar linkage system with telescoping air spring viscous dampers where the linkage element attached to the antenna remains vertical irrespective of the displacement of the flotation element. 
     FIG. 2A illustrates in greater detail one of the joints and its telescoping air spring viscous damper as used in FIG. 2. 
     FIG. 3 illustrates a combination of two four-bar linkage systems with a servo feedback stabilizing system where the linkage element attached to the antenna remains vertical irrespective of the displacement of the flotation element. 
     FIG. 3A illustrates the servo feedback stabilizing system as used in FIG. 3. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a single four-bar linkage system with preloaded torsion hairpin springs. A pivot support 10 is mounted on a flotation element 12 resting on the surface 14 of a body of water. A first bar 16 is mounted to pivot about the pivot support 10 at a point on the first bar between its end points. A second bar 18 is attached at a point between its end points by a first pivot joint 20 with a preloaded torsion hairpin spring to an end point of the first bar 16. A third bar 22 is attached at one of its end points by a second pivot joint 24 with a preloaded torsion hairpin spring to the end point of the first bar 16 opposite to the end point of the first bar attached to the second bar 18. FIG. 1A illustrates in more detail the second pivot joint 24 and its associated preloaded torsion hairpin spring 25. 
     A fourth bar 26 is attached at one end point by a third pivot joint 28 with a preloaded torsion hairpin spring to one end point of the second bar 18. The fourth bar 26 is attached at the end point of the fourth bar opposite to the end point attached to the second bar 18 by a fourth pivot joint 30 with a preloaded torsion hairpin spring to a point on the third bar 22 between its end points. All pivot joints 20, 28 and 30 have preloaded torsion hairpin springs similar to pivot joint 24. 
     An antenna 32 is attached to the second bar 18 at the end point of the second bar opposite to the end point of the second bar attached to the fourth bar 26. A counterweight 34 is attached to the third bar 22 at the end point of the third bar opposite to the end point attached to the first bar 16. This counterweight 34 maintains the antenna 32 in a fixed vertical orientation with respect to the surface of a body of water through pantographic action, irrespective of the angular motion and displacement of the other linkage elements. 
     FIG. 2 illustrates a single four-bar linkage system with telescoping air spring viscous dampers. A pivot support 40 is mounted on a flotation element 42 resting on the surface 44 of a body of water. A first bar 46 is mounted to pivot about the pivot support 40 at a point on the first bar between its end points. A second bar 48 is attached at a point between its end points by a first pivot joint 50 with a telescoping air spring viscous damper to an end point of the first bar 46. A third bar 52 is attached at one of its end points by a second pivot joint 54 with a telescoping air spring viscous damper to the end point of the first bar 46 opposite to the end point of the first bar attached to the second bar 48. FIG. 2A illustrates in more detail the second pivot joint 54 and its associated telescoping air spring viscous damper 55. 
     A fourth bar 56 is attached at one end point by a third pivot joint 58 with a telescoping air spring viscous damper to one end point of the second bar 48. The fourth bar 56 is attached at the end point of the fourth bar opposite to the end point attached to the second bar 48 by a fourth pivot joint 60 with a telescoping air spring viscous damper to a point on the third bar 52 between its end points. All pivot joints 50, 58, and 60 have telescoping air spring viscous dampers similar to pivot joint 54. 
     An antenna 62 is attached to the second bar 48 at the end point of the second bar opposite to the end point of the second bar attached to the fourth bar 56. A counterweight 64 is attached to the third bar 52 at the end point of the third bar opposite to the end point attached to the first bar 46. This counterweight 64 maintains the antenna 62 in a fixed vertical orientation with respect to the surface of a body of water through pantographic action, irrespective of the angular motion and displacement of the other linkage elements. 
     FIG. 3 illustrates a combination of multiple four-bar linkage systems with a servo feedback stabilizing system. A pivot support 110 is mounted on a flotation element 112 having a hollow space. The flotation element 112 rests on the surface of a body of water 114. 
     A first bar 116 is mounted to pivot about the pivot support 110 at a point on the first bar between its end points. A second bar 118 is connected at a point between its end points to the first bar 116 at the pivot support 110. A third bar 120 and fourth bar 122 are attached, each at one of its end points respectively, by a first pivot joint 124 and a second pivot joint 126 to respective opposite end points of the second bar 118. A fifth bar 128 is connected at a point between its end points by a third pivot joint 130 to the end point of the third bar 120 opposite to the end point connected to the second bar 118. The fifth bar 128 is connected at one of its end points by a fourth pivot joint 132 to an end point of the first bar 116. An antenna 134 is supported by the fifth bar 128 at the end point of the fifth bar opposite to the end point connected to the first bar 116. 
     A torque motor 136 is attached to the flotation element 112. An inclinometer transducer 138 is attached to the fifth bar 128 at a point between the end points of the fifth bar. An amplifier 140 is attached to the inclinometer transducer 138. The inclinometer transducer 138 measures the angular displacement from vertical of the antenna 134 and transmits a signal to the amplifier 140. The amplifier 140 magnifies the signal from the inclinometer transducer 138 and transmits a signal to the torque motor 136. The torque motor 136 responds to a signal from the amplifier 140 by turning the mast at the pivot support 110, thus maintaining the antenna 134 at the desired pointing angle. FIG. 3A illustrates the torque motor 136, inclinometer transducer 138, and amplifier 140 of the servo feedback system. Highly accurate active stabilization or antenna sensor pointing can be compensated or controlled by this simple servo feedback system. This servo system can measure the angular error difference from vertical due to wind and servo the antenna to the desired pointing angle. 
     A sixth bar 142 is connected at a point between its end points by a fifth pivot joint 144 to the fourth bar 122 at the end point of the fourth bar opposite to the end point connected to the second bar 118. The sixth bar 142 is connected at one of its end points by a sixth pivot joint 146 to the first bar 116 at the end point of the first bar opposite to the point which is connected to the fifth bar 128. A counterweight 148 is supported by the sixth bar 142 at the end point of the sixth bar opposite to the end point connected to the first bar 116. This counterweight 148 maintains the antenna 134 in a fixed vertical orientation with respect to the surface of a body of water through pantographic action, irrespective of the angular motion and displacement of the other linkage elements. 
     The flotation element 112 has a hollow space of sufficient size to hold the pivot support 110; bars 116, 118, 120, 122, 128, and 142; pivot joints 124, 126, 130, 132, 144, and 146; antenna 134; torque motor 136; inclinometer transducer 138; amplifier 140; and counterweight 148. The pivot support 110; bars 116, 118, 120, 122, 128 and 142; pivot joints 124, 126, 130, 132, 144, and 146; antenna 134; torque motor 136; inclinometer transducer 138; amplifier 140; and counterweight 148 are positioned within the hollow space of the flotation element 112 and extend therefrom when the flotation element 112 is deployed in the water. When this buoy is deployed on the ocean surface, the mast linkage which is folded within the buoy envelope, extends due to gravitational forces on the submerged weight and mast elements. Placing the elements of the linkage system within the body of the flotation element makes this flotation device more compact and convenient. This linkage will also provide a certain amount of isolation to the antenna due to the wave motion(heave) since wave motion induces vertical forces on the pivot and not directly on the mast. The importance of this is that the vertical amplitude displacement of the antenna can be reduced by manipulating the natural period and frequencies of the antenna/linkage against the forcing functions of the ocean waves on the buoy(pivot). 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.