Abstract:
An apparatus and method for sealing the barrel of an underwater gun between firings is disclosed. The apparatus comprises a valve that is moved between a sealing and non-sealing state by a valve-actuator. In some embodiments, the valve actuator is driven by gases that result when a round is fired.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This case is related to the following U.S. patent applications: Atty. Dkt. Nos.: 711-197us (Underwater Gun Comprising a Barrel-Adapter including a Barrel Seal), 711-198us (Underwater Gun Comprising a Plate-Type Barrel Seal), 711-199us (Underwater Gun Comprising a Passive Fluidic Barrel Seal), and 711-200us (Underwater Gun Comprising a Turbine-Based Barrel Seal), all of which were filed on even date herewith and all of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to underwater guns. 
       BACKGROUND OF THE INVENTION 
       [0003]    Underwater guns are useful as anti-mine and anti-torpedo devices. Recently, autonomous underwater vehicles (AUVs) have been fitted with underwater guns for torpedo defense and underwater “hunter-killer” CONOPs. 
         [0004]    A gun, especially one with a high muzzle velocity, cannot be fired when water is in its barrel. If a firing where to incur in a water-filled barrel, a very high breach pressure would result as the ignited propellant charge forces (or tries to force) the water out of the barrel. The likely result would be material failure of the barrel. 
         [0005]    The prior art is replete with approaches for waterproofing the barrel of an underwater gun, or for clearing water from its barrel before firing. U.S. Pat. No. 5,639,982 discloses a means for firing a fully automatic gun underwater using a blank barrel-clearance round. Blank barrel-clearance rounds are alternated with live rounds of ammunition. To begin the process, a blank barrel-clearance round is first detonated. This creates gas and steam within the chamber that forms a bubble at the muzzle end of the barrel, thereby displacing water from the chamber. A live round is then immediately fired. The process is repeated, whereby the subsequent detonation of a blank barrel-clearance round displaces any water that has re-entered the barrel subsequent to the firing of the live round. 
         [0006]    U.S. Pat. No. 5,648,631 discloses a spooled tape seal for sealing the barrel of an underwater gun. The system includes a tap that covers the opening of the gun barrel and sprockets for advancing the tape across the opening. Hydrostatic pressure keeps the tape pressed to the end of the barrel to create an effective seal. When a bullet is fired, it perforates the tape. During this brief period of egress, the exhaust gases from combustion of the propellant charge keep water from entering the barrel. Almost immediately, a non-perforated portion of the tape is advanced by the sprockets to cover the barrel opening. External hydrostatic pressure re-seats the tape, thereby preventing water from entering the barrel. 
         [0007]    U.S. Pat. No. 5,687,501 discloses a sealing plate for providing a watertight seal for a multi- or single-barreled underwater gun. The sealing plate provides one or more firing apertures in an otherwise solid surface. Between firings, the gun muzzle is sealed by a solid surface of the sealing plate. To fire a bullet, the sealing plate or muzzle rotates to align the gun muzzle with one of the firing apertures. This permits unimpeded egress. After the bullet fires, the plate or muzzle again rotates so that a solid portion of the sealing plate covers the muzzle. 
         [0008]    These are but a few of the many patents pertaining to various aspects of underwater gun design in general, and to the water-in-the-barrel problem, in particular. Not with standing the many approaches to the problem, no truly satisfactory approach has been developed for keeping water out of the barrel of an underwater gun between and during operation. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides an underwater gun having a barrel seal for preventing water from entering the barrel between the firing of rounds. 
         [0010]    In the illustrative embodiment, the barrel seal is a valve that is disposed in the barrel of a gun. The valve is operatively coupled to a valve actuator. The valve actuator is operable to open or close the valve, thereby unsealing or sealing the barrel. 
         [0011]    In accordance with the invention, the valve can be any of a variety of different types of valves, including, without limitation, a gate valve, a ball valve, and an iris valve. Furthermore, the valve actuator can take any one of a variety of different forms, such as, without limitation, a cylinder and piston arrangement or a motor. In some embodiments, the valve actuator includes, as a function of valve type, an arrangement for converting linear motion (e.g., of a piston, etc.) to rotational motion (e.g., to rotate the valve, etc.). 
         [0012]    In various embodiments, the valve actuator is driven via different forms of power. For example, in some embodiments in which the valve actuator comprises a cylinder and piston, the valve actuator is driven by the combustion gases that are generated as the round&#39;s chemical propellant is ignited during firing. In some other embodiments, the valve actuator is driven by electricity or hydraulics, among other forms of power. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [0013]      FIG. 1  depicts an underwater gun having a valve-type barrel seal in accordance with the illustrative embodiment of the present invention. 
         [0014]      FIG. 2  depicts a first embodiment of the underwater gun of claim  1 , wherein the valve is a gate valve having a piston-based actuation system, wherein the piston is driven by combustion gases. 
         [0015]      FIG. 3  depicts the underwater gun of  FIG. 2  in a firing state. 
         [0016]      FIG. 4  depicts a second embodiment of the underwater gun of claim  1 , wherein the valve is a ball valve having a piston-based actuation system, wherein the piston is driven by combustion gases. 
         [0017]      FIG. 5  depicts the underwater gun of  FIG. 4  in a firing state. 
         [0018]      FIG. 6  depicts a third embodiment of the underwater gun of claim  1 , wherein the valve is a iris valve having a motor-based actuation system. 
         [0019]      FIG. 7  depicts the iris valve of the underwater gun of  FIG. 6  in a closed state. 
         [0020]      FIG. 8  depicts the iris valve of the underwater gun of  FIG. 6  in an open state. 
     
    
     DETAILED DESCRIPTION 
       [0021]    The terms appearing below are defined for use in this specification, including the appended claims, as follows:
       Axially-oriented (or axial orientation) refers to an orientation that aligns with the longitudinal axis of an element. This orientation is orthogonal to a radial orientation.   Barrel is a narrow, hollow cylindrical portion of a firearm through which a projectile travels.   Bore is the hollow portion of the barrel through which a projectile travels during its acceleration phase.   Breech is an opening in the rear of a barrel of a gun where projectiles can be loaded.   Chamber is the portion of a barrel where a projectile is placed just prior to being fired. This is a high pressure containment area which is very precisely aligned with the bore of the barrel.   Fluidically coupled or fluidic communication means that liquid, gas, or vapor from a first region can flow to or otherwise affect a second region. For example, if two regions are fluidically coupled (or in fluidic communication), a pressure change in one of those regions might result in a pressure change in the other of the regions.   Muzzle is the opening at an end of the barrel where a projectile that has been fired exits the barrel.   Operatively coupled means that the operation of one device affects another device, wherein the devices need not be physical attached to one another. For example, a laser and a mirror are operatively coupled if a laser directs a beam of light to the mirror. An actuator and a valve are operatively coupled if the actuator actuates the valve, regardless of whether there other intermediary mechanisms between the actuator and the valve. Operatively-coupled devices can be coupled through any medium (e.g., semiconductor, air, vacuum, water, copper, optical fiber, etc.) and involve any type of force. Consequently, operatively-coupled objects can be electrically-coupled, hydraulically-coupled, magnetically-coupled, mechanically-coupled, optically-coupled, pneumatically-coupled, thermally-coupled, etc.   Radially-oriented (or radial orientation) refers to an orientation that is coincident with the radial direction of an element. See “axially-oriented.”       
 
         [0031]    The present invention pertains to guns that are intended for (1) use in an underwater environment and (2) firing rounds that include a chemical propellant. The underwater guns described herein will typically, although not necessarily, be fitted to AUVs. For clarity, gun  100  is typically depicted in the Figures as having a single round in the chamber or bore. It is to be understood, however, that gun  100  is typically a multi-shot weapon. 
         [0032]      FIG. 1  depicts underwater gun  100  having a valve-type barrel seal in accordance with the illustrative embodiment of the present invention. Gun  100  includes barrel  102 , chamber  104 , bore  108 , fire-control system  110 , valve  114 , and valve actuator  116 , interrelated as shown. A live round  112  is depicted in bore  108 . 
         [0033]    Barrel  102 , chamber  104 , and bore  108  are conventional features of most guns. Fire-control system  110  is basically a computer and ancillary elements that enable gun  100  to hit a target. The relative sophistication of any particular embodiment of fire-control system  110  is primarily a function of the intended application for gun  100 . That is, a relatively more sophisticated fire-control system is required for a relatively more autonomous application (e.g., for use in conjunction with an AUV, etc.). 
         [0034]    In a typical embodiment, fire-control system  110  interfaces with one or more sensors (e.g., sonar, radar, infra-red search and track, laser range-finders, water current, thermometers, etc.). The sensor input is used to develop a firing solution for a target. To the extent that gun  100  is located on an AUV, etc., fire-control system  110  advantageously takes into account movements of the AUV itself. And, when associated with an AUV, fire-control system  110  is operatively coupled to aiming and firing mechanisms. 
         [0035]    The fire-control system is not particularly germane to an understanding of the invention and, furthermore, is well understood by those skilled in the art. As a consequence, fire-control system  110  will not be described in further detail. 
         [0036]    Valve  114 , which in the illustrative embodiment is disposed at the muzzle end  106  of barrel  102 , functions as a barrel seal for gun  100 . Valve  114  has two primary states: one state in which the valve is “closed” and another state in which the valve is “open.” When valve  114  is closed, it prevents water from advancing into barrel  102 . When valve  114  is open, it unseals barrel  102 , thereby enabling round  112  to be fired. 
         [0037]    Valve  114  is controlled (i.e., moved between the two states) by valve actuator  116 . A variety of different actuation schemes can be used to actuate valve  114 . The selection of a particular type of actuator is dependent, to some extent, upon the specifics of valve  114  (e.g., gate valve, ball valve, iris valve, etc.) and the form of the power being used to drive actuator  116  (e.g., electricity, gas, etc.). 
         [0038]    In some embodiments, valve actuator  116  is operatively coupled to fire-control system  110 . This might be required to time the opening of valve  114  with the firing of a round, as a function of the actuation system. 
         [0039]    This specification now proceeds with a description of several embodiments of underwater gun  100 . These embodiments are distinguished from one another by the specifics of valve  114  and/or valve actuator  116 . 
         [0040]      FIGS. 2 and 3  depicts underwater gun  100  in which:
       the valve is a gate valve;   the valve actuator comprises a piston and cylinder; and   the valve actuator (a piston and cylinder arrangement) is driven by gases generated upon combustion of the projectile&#39;s chemical propellant.
 
 FIG. 2  depicts the barrel of gun  100  in a sealed state (i.e., valve closed) and  FIG. 3  depicts gun  100  during the firing of a live round (i.e., valve open).
         
         [0044]    Gun  100  of  FIG. 2  includes barrel  102 , bore  108 , fire-control system  110 , gate valve  214 , gas port  220 , channel  222 , cylinder  224 , and piston  226 , interrelated as shown. Live round  112  is depicted in bore  108 . 
         [0045]      FIG. 2  depicts gate valve  214  in a closed position. In this position, the gate valve seals barrel  102  against water intrusion. For the embodiment of gun  100  that is depicted in  FIG. 2 , some amount of water will of course be resident in the barrel between valve  214  and muzzle end  106  of barrel  102  when gate valve  214  is closed. 
         [0046]    With reference to  FIG. 3 , when round  112  is fired, combustion gases are generated (upon ignition of the round&#39;s chemical propellant). Combustion generates high pressures in bore  108  and the gun&#39;s chamber (not depicted). Some of these gases exit bore  108  through gas port  220 . Those gases that exit through gas port  220  are conducted, via channel  222 , beneath piston  226  in cylinder  224 . The increase in pressure in the region beneath the piston forces the piston “upward” (i.e., away from barrel  102 ). As piston  226  rises through cylinder  224 , gate valve  214  is withdrawn from barrel  102 . 
         [0047]    Upon firing, some of the combustion gases are blown out of muzzle end  106  of bore  108 . This has the effect of clearing any water that was residing in barrel  102  “downstream” of valve  214 . 
         [0048]    To the extent that gun  100  continues to fire rounds, the substantially continuous generation of combustion gases will support piston  226  such that valve  214  remains in its “open” state. As a consequence, bore  108  remains open to permit rounds to be fired from gun  100 . 
         [0049]    In some embodiments, cylinder  224  is closed to the ambient environment. In such embodiments, a spring or other device (not depicted) that is arranged to provide a restoring force is disposed within cylinder  224 . The restoring force urges piston  226  back toward barrel  102 . Once firing ceases, the pressure rapidly decreases in the region below piston  226  such that there will be insufficient pressure to overcome the restoring force that is provided by the spring, etc. As a consequence, piston  226  drops and valve  214  re-seats in barrel  102 , thereby blocking bore  108 . 
         [0050]    In some other embodiments, cylinder  224  is open to the ambient environment. In such an embodiment, the ambient water pressure bearing on piston  226  provides the restoring force that would otherwise be provided by a spring or other mechanism in a closed cylinder. 
         [0051]    In the embodiment of gun  100  that is depicted in  FIG. 2 , the valve actuator (i.e., piston  226  and cylinder  224 ) does not react to commands from fire-control system  110 . The response of the valve actuator is “automatic;” that is, it is based on the increase in pressure in the gun as a consequence of the combustion of a round&#39;s chemical propellant. 
         [0052]    Notwithstanding the aforementioned “automatic” valve actuation, timing of the valve&#39;s movement is important. It can be readily determined how much time is required for a round to reach the location of the valve, how much force is available from combustion to operate the valve actuator, and how much force will be required to actuate the valve and cause it to open with the requisite speed. As a function of the chemical propellant used in the round, the weight of the piston, and other factors, in some embodiments, a separate charge (in addition to the round&#39;s chemical propellant) will be required to actuate valve  214 . 
         [0053]    In fact, it is possible that valve  214  must start to move before live round  112  is fired. In such cases, a separate charge will be required, and it will need to be pre-fired (before the live round), so that pressure can build to a sufficient extent to move the piston. 
         [0054]    Another way to address the timing issue is to provide a round that exhibits a staggered acceleration profile. In particular, a round is provided with two or more separate charges of chemical propellant, the ignition of which is staged. As a consequence, the round is first accelerated, compresses gas in bore  108  and decelerates briefly until valve  214  fully withdraws (i.e., opens), and then is re-accelerated with the ignition of the second charge of propellant. 
         [0055]    In the illustrative embodiment that is depicted in  FIGS. 2 and 3 , the valve actuator is a piston and cylinder arrangement driven by combustion gases. In some other embodiments, other valve actuation arrangements known to those skilled in the art are suitably used, including, without limitation, a piston/cylinder arrangement that is hydraulically actuated, linkages that operably couple valve  214  to a motor, and the like. In these arrangements, valve actuation is not “automatic” in the sense previously described. As a consequence, in such embodiments, the actuation of valve  214  is responsive to information (e.g., a signal) from fire-control system  110 . An example of an embodiment in which valve actuation is under the control of fire-control system  110  is described in conjunction with  FIGS. 6-8 . 
         [0056]      FIGS. 4 and 5  depicts underwater gun  100  in which:
       the valve is a ball valve;   the valve actuator comprises a piston and cylinder; and   the valve actuator is driven by gases generated upon combustion of the projectile&#39;s chemical propellant.
 
 FIG. 4  depicts the barrel of gun  100  in a sealed state (i.e., valve closed) and  FIG. 4  depicts gun  100  during the firing of a live round (i.e., valve open).
         
         [0060]    Gun  100  of  FIG. 4  includes barrel  102 , bore  108 , fire-control system  110 , ball valve  414 , gas port  220 , cylinder  424 , piston  426 , rack  428 , and pinion gear  430 , interrelated as shown. Live round  112  is depicted in bore  108 . 
         [0061]      FIG. 4  depicts ball valve  414  in a closed position wherein valve orifice  415  does not align with bore  108  of barrel  102 . In this position, ball valve  414  seals barrel  102  against water intrusion. For the embodiment of gun  100  that is depicted in  FIG. 4 , some amount of water will of course be resident in the barrel between valve  414  and muzzle end  106  of barrel  102  when ball valve  214  is closed. 
         [0062]    Like the embodiment depicted in  FIGS. 2 and 3 , this embodiment of gun  100  also uses a piston and cylinder valve-actuation arrangement. Furthermore, rack  428  is coupled to piston  426  and extends through wall  425  of cylinder  424 . Teeth (not depicted) that are formed on rack  428  operatively engage pinion gear  430 . The pinion gear is, in turn, operatively coupled to ball valve  414 . This rack and pinion arrangement converts the linear motion of piston  426  to rotational motion that is used to rotate ball valve  414  between an open position and a closed position. 
         [0063]    Referring now to  FIG. 5 , when round  112  is fired, combustion gases are generated (upon ignition of the round&#39;s chemical propellant). Combustion generates high pressures in bore  108  and the gun&#39;s chamber (not depicted). Some of these gases exit bore  108  through gas port  220 . Those gases that exit through gas port  220  are conducted to cylinder  424 . The increase in pressure in region  422  near the entrance to cylinder  424  due to the presence of the combustion gases forces piston  426  to stroke through the cylinder. 
         [0064]    As piston  226  advances through cylinder  224 , pinion gear  430  is rotated via the movement of rack  428 . In turn, ball valve  414  rotates from a closed state, as depicted in  FIG. 4 , to the open state that is depicted in  FIG. 5 . In the open state, valve orifice  415  aligns with bore  108  of barrel  102 . Orifice  415  is, of course, appropriately sized to permit passage of round  112 . 
         [0065]    Upon firing, some of the combustion gases are blown out of muzzle end  106  of bore  108 . This clears any water that resides in barrel  102  “downstream” of valve  414 . 
         [0066]    A torsion spring (not depicted) that is operatively coupled to the ball valve  414  provides a restoring force to return piston  426  to its rest position at the “bottom” of cylinder  424 . When round  112  is first fired, the increase in pressure due to the rapid generation of combustion gases overcomes the restoring force of the spring and causes piston  426  to move through cylinder  424 . But as the combustion gases dissipate, the pressure drops, and piston  426  returns to its rest position. 
         [0067]    To the extent that gun  100  continues to fire rounds, the substantially continuous generation of combustion gases will support piston  426  such that valve  414  remains in its “open” state. As a consequence, bore  108  remains open to permit rounds to be fired from gun  100 . 
         [0068]    Like the embodiment of gun  100  that is depicted in  FIGS. 2 and 3 , the valve actuation system (piston  426 , cylinder  224 , etc.) does not react to commands from fire-control system  110 . The response of the valve actuator is “automatic;” that is, it is based on the increase in pressure in the gun as a consequence of the combustion of a round&#39;s chemical propellant. 
         [0069]    But as described in conjunction with the embodiment depicted in  FIGS. 2 and 3 , timing of the movement of valve  414  is important and is subject to the same considerations as valve  214 , including the possibility of using a separate, pre-fired charge and the option of a round that uses a staggered acceleration profile. 
         [0070]    Furthermore, in some other embodiments of gun  100 , other valve actuation arrangements known to those skilled in the art are suitably used, including, without limitation, a piston/cylinder arrangement that is hydraulically actuated, linkages that operably couple valve  414  to a motor, and the like. In these arrangements, valve actuation is not “automatic” in the sense previously described. As a consequence, in such embodiments, the actuation of valve  414  is responsive to information (e.g., a signal) from fire-control system  110 . An example of an embodiment in which valve actuation is under the control of fire-control system  110  is described below in conjunction with  FIGS. 6-8 . 
         [0071]      FIG. 6  depicts underwater gun  100  in which:
       the valve is an iris valve; and   the valve actuator comprises a motor.         
         [0074]    Gun  100  of  FIG. 6  includes barrel  102 , bore  108 , fire-control system  110 , controller  632 , motor  634 , and iris valve  614 , interrelated as shown. Live round  112  is depicted in bore  108 . 
         [0075]      FIG. 7  depicts iris valve  614  in a closed state and  FIG. 8  depicts the iris valve in an open state. The iris valve comprises a plurality of leaves  736 . Iris valves typically include a circumferentially-disposed rotatable ring that, when rotated, moves the leaves such that aperture  838  begins to form at the center of the valve. The aperture continues to open radially until it reaches its full size. 
         [0076]    In the closed state, the iris valve seals barrel  102  against water intrusion. For the embodiment of gun  100  that is depicted in  FIG. 6 , some amount of water will of course be resident in the barrel between valve  614  and muzzle end  106  of barrel  102  when iris valve  214  is closed. 
         [0077]    Iris valve  614  is operatively coupled, via appropriate linkages (not depicted), to motor  634 . The motor, typically an electrical motor, drives the opening and closing of iris valve  614 . In the previous embodiments, valve actuation was “automatic” in the sense that it was driven by combustion gases. But for the embodiment depicted in  FIG. 6 , the actuation of valve  614  is responsive to information coming from fire-control system  110 . 
         [0078]    More particularly, fire-control system  110  sends a signal to controller  632  at an appropriate time as a function of valve response, etc., to actuate motor  634  to change the state of valve  614 . With regard to timing, it is possible that due to the response of valve  614 , the valve might need to begin opening before a round is fired. In such a case, after fire-control system  110  has a solution but before it sends a command to fire, it sends a signal to controller  632  to begin opening valve  614 . Valve  614  also closes via the action of fire-control system  110 . 
         [0079]    In some other cases, the fire-control system  110  sends a signal to controller  632  that indicates that a round is about to be fired. The controller then actuates motor  634  to open valve  614  after a first delay, wherein the delay is based on the time it takes for a pressure wave from combustion gases to arrive at the valve. In the case of the firing of a single round, valve  614  closes after a second delay, wherein the second delay is based on the time it takes for the round to transit valve  614 . 
         [0080]    The operation of this embodiment is analogous to the operation of an underwater camera. In fact, in a further embodiment, an electronically-controlled shutter such as adapted from an underwater camera serves as the valve-based barrel seal. The shutter is simply activated by fire-control system  110 . 
         [0081]    It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.