Propulsion and directional control mechanism for an underwater device
DESCRIPTION 
     1. Technical Field 
     This invention pertains to propulsion and directional control mechanism for an underwater device and, more particularly, to such mechanism for a mobile mine. A gas propellant tank delivers propellant gas to a turbine engine which is connected to a propeller for rotation thereof through a speedreduction gearbox. Directional control means includes a pair of movable fins and an actuation system therefor. The components are integrated in a relation to provide a minimum size and maximum performance with optimized structural relations. 
     2. Background Art 
     There is considerable prior art relating to propulsion systems for underwater devices, particularly torpedoes. Known propulsion systems have used a fluid under pressure, steam or electricity as a power source. It is also generally known to generate a hot gas for driving a gas turbine by burning a solid propellant. This prior art has not associated a gas propellant tank or chamber with a gas turbine having a common wall with nozzles for directing gas from the chamber to the turbine and with a turbine wheel offset from the axis of rotation of a tubular propeller shaft, to provide a substantially direct flow of gas from the propellant chamber through the tubine to an exhaust passage extending through the tubular propeller shaft, nor provided speed reduction gearing interconnecting the turbine wheel and the propeller shaft and with a common mounting for the bearing means for the aforesaid rotating components to provide assured bearing alignment. 
     The prior art also discloses various mechanisms for achieving directional control of an underwater device including the use of a pair of separatelypositionable fins which can be separately controlled to produce heading changes in any direction of the underwater device. This prior art has not disclosed a pair of fins separately controllable by a pair of fluid cylinders supplied with fluid as controlled by a pair of control valves associated one with each cylinder and with each cylinder having a piston rod and piston, with the piston carrying a rack meshing with a pinion on a rotatable shaft carrying a fin and wherein the fluid cylinders can use hot gas exhausted from a propellant gas chamber which drives the propulsion system of the underwater device and with such a construction fitting into a small space to contribute to the over-all minimum size of the underwater device. 
     DISCLOSURE OF THE INVENTION 
     A primary feature of the invention is to provide a new and improved propulsion and directional control mechanism for an underwater device and, more particularly, for a mobile mine which uses a solid propellant as a power source for driving a gas turbine with aft exhaust through the hull of the device and with a minimum over-all length being achieved, in part, by a unique dual control actuation system for a pair of directional control fins. 
     More particularly, the underwater device has a tail cone with bearing means for rotatably mounting a tubular propeller shaft and the turbine wheel of a gas turbine as well as gearing of a speed-reduction gearbox interconnecting the turbine wheel and the propeller shaft to assure alignment of the bearings of the various components. The axis of rotation of the turbine wheel is offset from the axis of rotation of the propeller shaft wherein gas can flow directly from a gas propellant chamber through the turbine to an exhaust passage extending through the propeller shaft for discharge aft of the device. The gas turbine and the gas propellant chamber share a common wall with nozzles therein for directing flow of gas from the chamber to the turbine wheel. 
     Additionally, directional control of the underwater device is achieved by structure including a pair of fins mounted at the aft end of the tail cone on a pair of transversely-extending, individually rotatable shafts, each having a pinion. A pair of fluid cylinders are associated one with each of the rotatable shafts and each has a piston with a piston rod extending therefrom having a rack for association with the pinion and with the piston rods extending longitudinally alongside the exhaust passage for the propellant gas. Each of the fluid cylinders may have pressure fluid directed thereto under the control of a pair of control valves associated one with each of the fluid cylinders and with the fluid pressure source either being hot gas exhausted from the propellant gas chamber or hydraulic fluid stored in a hydraulic accumulator. 
     An object of the invention is to provide a mobile underwater device comprising, propulsion means including a hollow propeller shaft mounting a propeller, a gas turbine having a turbine wheel, a gas propellant chamber having an outlet communicating with the turbine wheel, a gas exhaust passage from the turbine extending through the hollow propeller shaft, and said turbine wheel having its axis of rotation offset from the axis of rotation of the hollow propeller shaft to enable said gas exhaust passage to generally align with the center of said hollow propeller shaft. 
     Still another object of the invention is to provide a propulsion mechanism as defined in the preceding paragraph wherein said gas propellant chamber and gas turbine share a common wall with gas nozzles extending through said common wall. 
     A further object of the invention is to provide a mobile underwater device and, more particularly, a mobile mine comprising, directional control means including a pair of movable fins at the aft end of the device, a pair of rotatable shafts extending transversely of said device and each mounting one of said fins, and means for positioning said fins by rotation of said shafts including a pair of fluid cylinders associated one with each of the rotatable shafts and each having a piston and a linearly movable piston rod, and a gear connection between each piston rod and associated rotatable shaft for converting linear movement of the piston rod into movement of a fin. 
     An additional object of the invention is to provide a mobile mine as defined in the preceding paragraph wherein a pair of control valves are associated one with each fluid cylinder for controlling the position of the pistons and fins and wherein fluid under pressure supplied to the control valves can either be derived from exhaust gas from a gas propellant chamber or hydraulic fluid from a hydraulic accumulator. 
     An additional object of the invention is to provide a mobile underwater device having a tail cone, a rotatable propeller shaft, a gas turbine having a turbine wheel providing a drive for the propeller shaft, a speed reduction gearbox connected between the turbine wheel and the propeller shaft and bearing means for said propeller shaft, turbine wheel and speed reduction gearbox which are all mounted on said tail cone to achieve alignment of said bearings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal central section of the after part of an underwater device, such as a mobile mine; 
     FIG. 2 is a schematic perspective view of the speed reduction gearing between a turbine wheel and a tubular propeller shaft; 
     FIG. 3 is a partial section, taken generally along the line 3--3 in FIG. 1 and on an enlarged scale; and 
     FIG. 4 is a fragmentary view of an alternate source of fluid pressure for the operation of the directional control fins. 
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     The underwater device is shown in the form of a mobile mine, with the after part thereof shown in FIG. 1. A tail cone, indicated generally at 10, has a generally frusto-conical front section 11 with a pair of interior chambers 14 and 15 and a generally cylindrical section 16 with an annular surrounding spaced flange 17 defining a chamber 18 therebetween. Additionally, the tail cone 10 has an aft section 20 rigidly associated with the front section 11 by a series of fasteners in the form of threaded bolts 21 which interconnect a pair of annular elements 25 and 26 integral with the tail cone front section 11 and aft section 20. The annular element 25 is formed integral with the tail cone front section 11 by integral inlet guide vanes 27 and 28. The annular element 26 is integrally associated with the tail cone aft section 20 by radially-extending stator and stabilizer structure 30 positioned at a plurality of circumferentially-spaced locations about the tail cone aft section 20. 
     The space between the body parts of the tail cone front section 11 and aft section 20 and the annular elements 25 and 26 provides an annular channel for flow of water past a propeller 40 having a tubular propeller shaft 32 positioned partly in the chamber 18 and having a plurality of radially-extending blades 33. The inlet guide vanes 27 and 28 as well as additional inlet guide vanes, not seen in FIG. 1, and which are spaced circumferentially about the tail cone front section 11 direct the flow of water past the propeller blades, with the water then flowing through the stator and stabilizer structure 30 and past directional control means in the form of a pair of independently positionable fins 35, discussed more particularly hereinafter. 
     The propulsion means in addition to the propeller 40 includes a propellant gas chamber or tank 42 mounted in the tail cone chamber 14, a gas turbine 43 also mounted in the chamber 14, and a speed-reduction gearbox, indicated generally at 44, which is positioned in the chamber 15 and drivingly interconnects the gas turbine and the propeller shaft 32. 
     The gas propellant chamber 42 contains a solid propellant which, when burned, produces a hot gas under pressure which can flow through an outlet 47 to the gas turbine. The propellant chamber 42 and gas turbine 43 share a common wall 48 having nozzles 49 for directing the hot gas from the outlet 47 to a turbine wheel 50 of the gas turbine. The gas exhausts from the gas turbine through a passage 51 to an exhaust passage including a tubular member 52 which communicates with a passage 53 formed in the cylindrical section 16 of the tail cone front section 11 and which, in turn, communicates with a tube 54 opening to the aft end of the tail cone aft section 20. With the tubular propeller shaft 32 surrounding the cylindrical section 16, the exhaust gas effectively exhausts through the propeller shaft. 
     The turbine wheel 50 is on a shaft 60 for rotation about an axis offset from the axis of rotation of the propeller shaft 32 to enable substantially straight-through gas flow from the propellant gas chamber 42 to the exhaust passage for discharge aft of the mobile mine. As seen particularly in FIG. 2, the speed-reduction gearbox 44 has three gear meshes to convert gas turbine output to the desired rotational speed for the propeller 40. The turbine wheel shaft 60 has a gear 61 meshing with a gear 62 on a shaft 63, with the latter shaft having a gear 64. The gear 64 meshes with a gear 65 on a shaft 66 having a gear 67 which meshes with an external gear 68 carried on the tubular propeller shaft 32. This drive train is accurately located and avoids the use of a flexible coupling to connect to the propeller shaft by having all of the bearing means for the rotatable components mounted to the unitary tail cone structure. This includes the bearing means 70 and 71 for the turbine wheel shaft 60 as well as the bearing means for the shafts of the speed-reduction gearbox and the bearings 72 and 73 which rotatably mount the propeller shaft 32. 
     The directional control means includes the pair of fins 35, previously referred to, which are individually mounted, one in each of a pair of rotatable shafts 80 and 81 (FIGS. 1 and 3) extending transversely of the mobile mine. Each shaft is rotatably supported by a pair of bearings at opposite ends thereof with the bearings for the shaft 80 being shown at 82 and 83 and the inboard bearing for the shaft 81 being shown at 84. As seen in FIG. 3, the shafts 80 and 81 are in alignment and terminate at their inner ends adjacent the sides of the exhaust member 54 and each shaft mounts a pinion gear 85 and 86, respectively. 
     The positioning of the fins is controlled by rotative postioning of the shafts 80 and 81 independently of each other and with each shaft being positioned by operating mechanism, including a fluid cylinder. A fluid cylinder 90 is located within the cylindrical section 16 of the tail cone and has a movable piston 91 therein urged in one direction by a spring 92 and having a piston rod 93 extending therefrom having a rack 94 which meshes with the pinion gear 85. Fluid pressure can be applied to the piston 91 in opposition to the force of the spring 92 for positioning of the associated fin under the control of one of a pair of control valves 95 and 96 located within the chamber 14 and having a control fluid line 97 extending to the cylinder 90. 
     A second fluid cylinder 100 is shown in phantom line in FIG. 1 since, as seen in FIG. 3, it is located above the line along which the sectional view of FIG. 1 is taken. The fluid cylinder 100 has a construction the same as the fluid cylinder 90 with a piston having a piston rod 101 having a rack which coacts with the pinion gear 86. The other of the control valves 95 and 96 controls the delivery of fluid pressure to the fluid cylinder 100 through a fluid control line 104. 
     The fluid under pressure selectively delivered to the fluid cylinders 90 and 100 under the control of the control valves 95 and 96 is hot gas under pressure generated within the gas propellant chamber 42 and which is delivered to the control valves through a line 110 (FIG. 1). Alternatively, the fluid pressure can be provided by hydraulic fluid and, as seen in FIG. 4, a hydraulic accumulator 115 has hydraulic fluid stored under pressure and which is delivered to the control valves 95 and 96 through a fluid line 116. 
     The pistons in the fluid cylinders 90 and 100 are individually movable in order to produce heading changes in any direction, by inducing body roll of the mobile mine. With the dual fin construction, the mobile mine will bank as it turns. The fluid cylinders enable the use of exhaust gas from the propellant gas chamber for control of the fins and the use of the piston rods and rack and pinion gear structure enable disposing the directional control mechanism within a small space in an interior chamber 120 in the tail cone aft section 20. 
     The disclosed mobile mine has minimum overall length and utilizes a hot gas under pressure provided by burning of a solid propellant to achieve propulsion by driving a gas turbine with exhaust aft of the mobile mine through the hull thereof and with dual control of the directional control fins and powering thereof being optionally derived from the same source of gas as used for propulsion.