Abstract:
An invention disclosed herein pertains to a thruster suitable for underwater vehicles. Such a thruster includes a steerable duct and propeller. The thruster motor, the two directional servo motors and all necessary electronics are contained in a single fluid filled and pressure compensated container. This is made possible, by a compact steering mechanism that allows the propeller and duct to be steered about the pitch and yaw axis of the vehicle and a spherical rolling seal which allows the fluid in the thruster to be maintained at a pressure of 2-5 psig. A gimbal that features a ring drive element enables efficient use of space. An actuation to drive the thruster may fit inside the ring drive element.

Description:
RELATED DOCUMENT  
       [0001]     Priority is hereby claimed to Provisional U.S. Patent Application Ser. No.  60 / 619 , 157 , filed on Oct. 15, 2004, the entirety of which is hereby incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     Underwater vehicles are frequently propelled by means of a single thruster that is pivoted to control the vehicle in pitch and yaw. U.S. Pat. No. 6,572,422 (the contents of which are fully incorporated herein by reference) teaches one such arrangement in which the motor driving the propeller is housed in an oil-filled, water-tight housing that is then pivoted about the pitch and yaw axis by two servomotors that are themselves housed in separate oil-filled, water-tight housings, all controlled by electronics which are themselves mounted in their own oil-filled, water-tight housings. This system requires a large pressure compensator consisting of a pressurized oil reservoir and associated plumbing to accommodate the changes in oil volume due to pressure and temperature variation. This results in a large number of hoses and waterproof cables and connectors and a heavy, bulky assembly.  
         [0003]     An object of an invention hereof is to contain the thruster motor, the two servomotors, the electronics, and the pressure compensation in a single oil-filled housing. This results in a smaller, lighter package.  
       SUMMARY  
       [0004]     An invention hereof is directed to a propulser suitable for use in all types of underwater vehicles. Such a propulser contains the means for propelling the vehicle (the thruster), the means for directing the vehicle (the actuators), the means of maintaining an internal pressure slightly greater than the external pressure (the compensators), and the control electronics to drive the thruster motor and the two actuator motors, all housed in a single, pressure housing filled with oil or a similar inert fluid. In addition to several static o-ring seals, such a propulser uses a spherical rolling seal, which allows the thruster to be pivoted about two axes while still maintaining a pressure-tight seal.  
         [0005]     The rolling spherical seal is a thin flexible membrane. The main part of the seal is formed as a section of a sphere, approximately symmetrical about its equator. The two ends of the seal are cast in the form of a bead to provide a means of securing the ends of the seal and to provide surfaces to seal against. When installed, the seal is folded back on itself as shown in  FIG. 12 . The center of rotation of the thruster should preferably correspond to the center of the spherical section of the seal. 
     
    
     BRIEF DESCRIPTION OF FIGURES  
       [0006]      FIG. 1  is an isometric view of a generic underwater vehicle and defines Pitch and Yaw axes for reference below.  
         [0007]      FIG. 2  shows a complete thruster assembly  2  with a stator  4  and a propeller  6  in place. One of two pressure compensator assemblies  8  is shown. The thruster assembly  2  is symmetrical, so it will be understood that there is another compensator assembly  8  on the opposite side of the thruster assembly  2 .  
         [0008]      FIG. 3  shows the thruster assembly  2  with the stator  4  and the propeller  6  removed for clarity. It also shows the orientation of the two section views, A-A and B-B.  
         [0009]      FIG. 4  shows SECTION B-B of the thruster assembly  2 . This section passes through the pressure compensator assemblies  8 .  
         [0010]      FIG. 5  shows SECTION A-A of the thruster assembly  2 .  
         [0011]      FIG. 6  shows a mechanism to rotate the thruster about the pitch and yaw axis, with a pressure vessel  16 , compensator assemblies  8 , and all other components not required to move the thruster, removed for clarity.  
         [0012]      FIG. 6A  shows a gimbal assembly in side view and section view.  
         [0013]      FIG. 7  shows an actuator group deflected fully to the right, about the yaw axis (approximately 21 degrees), clockwise as viewed from above.  
         [0014]      FIG. 8  shows the actuator group deflected fully to the left, about the yaw axis (approximately 21 degrees), counterclockwise as viewed from above.  
         [0015]      FIG. 9  shows the actuator group deflected fully up, about the pitch axis (approximately 21 degrees), clockwise as viewed from the right.  
         [0016]      FIG. 10  shows the actuator group deflected fully down, about the pitch axis (approximately 21 degrees), counterclockwise as viewed from the right.  
         [0017]      FIG. 11  shows a rolling spherical seal  26 , as it rotates from −16 degrees to +16 degrees.  
         [0018]      FIG. 12  shows the rolling spherical seal  26  in section view, as it rotates from −16 degrees to +16 degrees.  
         [0019]      FIG. 13  shows the thruster assembly with the thruster  28  deflected down 16 degrees.  
         [0020]      FIG. 14  shows the rolling seal in its unfolded condition.  
         [0021]      FIG. 15  shows the folded rolling seal in cross-section.  
         [0022]      FIG. 16  illustrates a spur-bevel gear assembly. 
     
    
     DESCRIPTION  
       [0023]     Underwater vehicles need to propel themselves and control their direction of travel. A common configuration for underwater vehicles is shown in  FIG. 1 . A thruster assembly  2  can be pivoted to control the vehicle in pitch and yaw defined in  FIG. 1 .  
         [0024]      FIG. 2  illustrates the thruster assembly  2 . Propulsion is provided by means of a non-rotating duct  4 , containing a propeller  6 . The mechanical and electrical components of the thruster  2  are contained in a pressure-tight housing  16  which is filled with an incompressible, non-conducting, non-corrosive fluid, such as mineral oil. The fluid is maintained at a pressure approximately 2-5 psi higher than the pressure of the surrounding fluid by a pair of pressure compensators  8 .  
         [0025]      FIG. 3  illustrates the thruster assembly  2  with the duct  4  and propeller  6  removed for clarity. Referring to  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 6A  the thruster assembly  2  consists of a baseplate  30  to which is rigidly mounted a trunnion mount  40 . The trunnion mount  40  supports servo motor assemblies  50 A and  50 B. The trunnion mount  40  also supports spur-bevel gear assemblies  46 A and  46 B through trunnion pins  44 A and  44 B on bearings  42 A and  42 B.  
         [0026]     The spur-bevel gear assemblies  46 A and  46 B support a gimbal  39  through the bearings  32 A and  32 B. The gimbal assembly  39  supports a forward pressure housing  14  through forward pressure housing supports  24 A and  24 B, which rotate on bearings  32 A and  32 B. The forward pressure housing  14  supports the duct  4 . The forward pressure housing  14  also supports the thruster motor gearbox assembly  28 . The thruster motor-gearbox assembly  28  supports the propeller  6 .  
         [0027]     The bearings  42 A,  42 B,  32 A, and  32 B allow the forward pressure housing  14  and all components supported by it to rotate about the pitch and yaw axes. This rotation is controlled by a gear train that starts with spur gears  48 A and  48 B of servo-motor assemblies  50 A and  50 B. These spur gears drive the spur-bevel gear assemblies  46 A and  46 B, see  FIG. 16 . A spur gear  47  is rigidly attached to a yaw bevel gear  49  and rotates on bearing  32 . A yaw bevel gear  49  on each of the spur-bevel gear assemblies  46 A and  46 B meshes with a ring bevel gear  20 . The ring bevel gear  20  is supported by the gimbal  39  through a ring bevel gear support  36  which rotates on a bearing  38 .  
         [0028]     The ring bevel gear  20  also meshes with a pitch bevel gear  22 . The pitch bevel gear is rigidly attached to the forward pressure housing support  24 A, which, as already discussed, supports the forward pressure housing  14 , so that the forward pressure housing  14  will move with the forward pressure housing support  24 A.  
         [0029]      FIG. 6 ,  FIG. 6A ,  FIG. 7 ,  FIG. 8 ,  FIG. 9 , and  FIG. 10  illustrate the operation of the directional control of the thruster assembly  2 . The forward pressure housing  14  and the thruster motor gearbox assembly  28  are omitted from these views for clarity. However, it is understood that the forward pressure housing  14  and therefore the thruster motor gearbox assembly  28  will move with the forward pressure housing supports  24 A and  24 B.  
         [0030]     When the spur gears  48 A and  48 B drive the spur gears  47 A and  47 B in the same direction as each other, as illustrated in  FIG. 7  and  FIG. 8 , two yaw bevel gears  49 A and  49 B will bear equally against the ring bevel gear  20 . The ring bevel gear  20  is unable to rotate about its own axis and therefore acts through the ring bevel gear support  36  and bearing  38  to rotate the gimbal assembly  31  around the yaw axis.  
         [0031]     When the spur gears  48 A and  48 B drive the spur gears  47 A and  47 B in opposite directions, from each other, as depicted in  FIG. 9  and  FIG. 10 , the yaw bevel gears  49 A and  49 B act on the ring bevel gear  20  in opposite directions. This will cause the ring bevel gear  20  to rotate about its own axis. The ring bevel gear  20  will then drive the pitch bevel gear  22  which will in turn rotate the forward pressure housing support  24 B about the pitch axis.  
         [0032]     By driving the spur gears  47 A and  47 B by differing rotational amounts, any combination of rotations about the pitch and yaw axis is possible, within the mechanical limits of the device. Also, the orientation of the thruster assembly  2  is somewhat arbitrary and the thruster assembly  2  may be rotated so that the axis labeled yaw and pitch may point in any direction.  
         [0033]     Another feature that is important to the function of the thruster assembly  2  is the rolling spherical seal  26 . The rolling spherical seal  26  is illustrated in an unfolded configuration in  FIG. 14 . The seal  26  is constructed of a flexible, waterproof material such as urethane or silicon.  FIG. 14  shows the shape of the seal “as cast”.  FIG. 15  provides a section view of the seal  26  in the unfolded configuration. The seal  26  consists of an outer bead  26 A, an inner bead  26 B, and a connecting skirt  26 C. The connecting skirt  26 C is roughly spherical in cross-sections as shown in  FIG. 15 . Angles E 1  and E 2  are approximately equal. The inner radius of the seal  26 , RI, is approximately equal to the outer radius of the forward pressure housing  14 .  
         [0034]     For a representative embodiment having a pressure housing that is approximately 9.5 in. (241.3 mm) long, with an oil volume of about  50  in 3  (819 cm 3 ), a silicone seal of 0.031 in. (0.787 mm) thick is reasonable. The pressure across such a seal can be approximately 3 psi. The seal gap can be on the order of between 0.09-0.125 in (2.3-3.18 mm). A reasonable motor to use for the servo motors  50 A and  50 B is available from MicroMo Electronics, Inc. of Clearwater, Fla., a member of the Faulhaber Group, 2444 motor series 30/1 415:1 reduction. A suitable thruster motor is available from AVEOX of Simi Valley, Calif., model 1817, combined with model 017P 10:1 planetary gearbox available from CGI, Inc., of Carson City, Nev. The deflection of the propeller and duct about the pitch and yaw axes is approximately ±15°.  
         [0035]     On installation, the outer bead  26 A is rolled back 90° and the seal is folded back on itself. When the seal  26  is at 0° deflection, i.e. the outer bead  26 A is parallel to the inner bead  26 B, the fold of the seal  26  is at approximately the equator of the spherical connecting skirt  26 C. The seal in its installed shape is shown in  FIG. 11  and in cross section in  FIG. 12 . These figures also illustrate how the seal changes shape as it is rolled from −16° to +16°.  
         [0036]      FIG. 13  shows the rolling spherical seal  26  installed in the thruster assembly  2 . The outer bead  26 A is trapped between the sealing ring  18  and the forward sealing ring  10 . The inner bead  26 B is trapped between a pressure housing clamping ring  34  and the forward pressure housing  14 . The connecting skirt  26 C is supported by the forward sealing ring  10  and the seal fairing  12  outboard and by the forward pressure housing  14  inboard. The internal pressure of the thruster assembly  2  helps maintain the shape of the seal. The sealing ring  18  has a small lip that both traps the outer bead  26 A and helps push the skirt against the forward sealing ring  10 , thereby preventing the seal from bulging out. In operation, the seal rolls back and forth between the forward sealing ring  10  and the seal fairing  12  outboard and the forward pressure housing  14  inboard as the pressure housing  14  rotates about the pitch and yaw axis either individually or in any combination of the two.  
         [0037]     Many techniques and aspects of the inventions have been described herein. The person skilled in the art will understand that many of these techniques can be used with other disclosed techniques, even if they have not been described as being used together. Thus, the fact that a sub-combination of features that are described separately, may not be described in sub-combination, does not mean that the inventor does not regard any such sub-combination as an invention that is disclosed herein.  
         [0038]     This disclosure describes and discloses more than one invention. The inventions are set forth in the claims of this and related documents, not only as filed, but also as developed during prosecution of any patent application based on this disclosure. The inventor intends to claim the various inventions to the limits permitted by the prior art, as it is subsequently determined to be. No feature described herein is essential to each invention disclosed herein. Thus, the inventor intends that no features described herein, but not claimed in any particular claim of any patent based on this disclosure, should be incorporated into any such claim.  
         [0039]     An abstract is submitted herewith. It is emphasized that this abstract is being provided to comply with the rule requiring an abstract that will allow examiners and other searchers to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, as promised by the Patent Office&#39;s rule.  
         [0040]     The foregoing discussion should be understood as illustrative and should not be considered to be limiting in any sense. While the inventions have been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventions as defined by the claims.  
         [0041]     The corresponding structures, materials, acts and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed.