Patent Publication Number: US-6216626-B1

Title: Flow release elastomeric ejection system

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an elastomeric vehicle launching system, and more particularly to a low noise, low volume, low elastomeric strain impulse fluid delivery apparatus of concentric elastomeric rings. 
     2. Description of the Prior Art 
     Impulse fluid flows are used to launch vehicles from submarine platforms. Launch systems in the prior art include the single stroke reciprocating pump, and the rotary air turbine pump. Additionally, elastomeric ejection systems have been developed, which store impulse fluid in charged el-astomeric bladders. 
     The single stroke reciprocating pump converts pneumatic potential energy from compressed air stored in a flask into working fluid kinetic energy. The pump utilizes a massive piston apparatus to transfer sufficient working fluid, such as seawater, to launch a projectile. The system has proven reliable, but has significant disadvantages. Its complexity results in high system and maintenance cost, and the rapid conversion of pneumatic potential energy into the vehicle kinetic energy results in significant radiated noise. 
     The air rotary turbine pump also converts potential energy in the form of compressed air stored in a flask into kinetic energy of a working fluid. An air turbine drive unit is joined with a rotary impeller pump via a speed reduction unit. This system suffers from disadvantages similar to those of the single stroke reciprocating pump. An alternative type of launch system is the elastomeric ejection system (EES) which addresses the problems of the single stroke reciprocating pump and the air rotary turbine pump. U.S. Pat. No. 4,848,210 discloses a n elastomeric impulse energy storage and transfer system. The system of this patent is adapted to a torpedo launch system wherein an elastomeric bladder is distended by filling it with pressurized fluid. When a fluid impulse is desired, the elastomeric bladder discharges its volume of working fluid to eject a projectile from the launch system into the surrounding liquid. The elastomeric bladder used is generally spherical, containing an expanded volume sufficient to fill the launch tube and the launch way forward of the launch tube. 
     U.S. Pat. No. 5,200,572 discloses an EES bladder, which has an elevation of frusto-ellipsoidal configuration and an ellipsoidal sectional plane parallel to the base of the bladder. The bladder of this patent is aimed at achieving a smooth and even flow of impulse fluid from the bladder to further reduce radiated noise. 
     U.S. Pat. No. 5,231,241 further discloses an EES configuration in which a submarine hull partially defines the volume of fluid stored in the elastomeric bladder. An impulse tank is defined by the volume between the inner hull and an elastomeric sheet. Pressurized liquid causes the diaphragm to expand within the outer hull to generate the required potential energy for a launch. U.S. Pat. No. 5,231,241 is hereby incorporated by reference. 
     The above EES systems suffer from cavitation noise following launch. When the finite volume of fluid in the bladder is exhausted a low pressure region forms, causing cavitation on the inside surface of the elastomeric bladder. U.S. Pat. No. 5,410,978 discloses a flow-through EES aimed at preventing cavitation noise. A cylindrical elastomeric bladder is disposed within a bypass tube, open at one end. When the bladder is filled with fluid, the walls of the bladder contact the walls of the bypass tube at a sealing ring, sealing the system from the outside fluid atmosphere. When the fluid in the bladder is discharged, the bladder unseats from the bypass tube, allowing free flow of fluid from the outside fluid atmosphere toward the impulse fluid. 
     Another patent further illustrative of the art is U.S. Pat. No. 5,645,006 which discloses a bladder assembly for retaining fluid under pressure. 
     A primary disadvantage of prior art EES systems is the high level of elastic strain on the charged bladder resulting in unstable bladder geometry and reduced material cyclic life. A further disadvantage is the undesirable cavitation noise which can occur following launch. Another disadvantage is that large bladder volumes are required to ensure successful vehicle launch before a bladder is exhausted. Further, the prior art flow through EES also suffer from undesirable system complexity. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general purpose and primary object of the present invention to provide an improved elastomeric ejection system (EES) for delivering impulse fluid to a vehicle. 
     A primary object of the invention is to provide a low volume launch system, which produces a minimal amount of radiated noise. 
     A further object of the invention is to provide a system with a long material cyclic life. 
     A still further object of the invention is to provide a mechanically simple, low cost EES. 
     In furtherance of the purpose and objects of the invention, a flow release elastomeric ejection apparatus and assembly are provided, featuring a ring-type diaphragm of concentric elastomeric rings, able to accept pressurized fluid and storing elastic potential energy in shear strain. 
     The ring diaphragm of the assembly comprises a series of concentric elastomeric rings, coupled to one another and alternating with rigid rings. These rings radiate inward toward a central disc to form an impermeable diaphragm. The ring diaphragm is adapted to be incorporated within a launch system such that pressurized fluid can be presented to an inner side of the diaphragm. Thus, the diaphragm is placed across an opening between two separate volumes of fluid. For example, the ring diaphragm can be attached such that it partially defines an impulse tank. When fluid pressure is increased on the inner side of the ring diaphragm, the elastomeric rings deform in shear strain to accept the additional fluid. Potential energy for launch is stored in the strained rings. Fluid release provides the impulse energy required for a launch and allows the ring diaphragm to return to its resting position. 
     A preferred flow release aspect of the invention comprises a one-way central check valve, which is a modified central disc. The check valve includes cut-outs in the central disc and valve flaps having seated and open positions in relation to the cut-outs. Following launch, excess fluid pressure on an outer side of the ring diaphragm causes the valve flaps to unseat and swing open, allowing fluid to flow through the ring diaphragm behind the impulse fluid. The resulting fluid pressure equilibration across the ring diaphragm prevents cavitation noise and makes a smaller impulse fluid volume feasible. 
     A further aspect of the present invention is an integrated vehicle launch assembly including the ring diaphragm of the invention. The ring diaphragm partially defines an impulse tank within the outer hull of a submarine. A pump transfers fluid from a free flood area to charge the impulse tank and the ring diaphragm. Launch is achieved by opening a slide valve connecting the impulse tank to a launch tube containing the launch vehicle. As the ring diaphragm deflates, the impulse fluid flows from the impulse tank into the launch tube forcing the vehicle out of the launch tube. Following launch, the check valve is forced open by fluid pressure in the free flood area, allowing fluid to flow from through the ring diaphragm into the impulse tank and toward the launch tube. 
     The ring diaphragm of the present invention will provide a long material cyclic life because the elastomeric rings are placed in shear strain (as opposed to extension), thereby subjecting the material to milder levels of strain than required of prior art elastomeric bladders. Further, the check valve feature of the invention prevents noisy cavitation by allowing free flow of fluid through the ring diaphragm from outside after launch. The check valve also makes possible a low overall system volume, because rapid deceleration of the impulse fluid is avoided. The central check valve is an optional but preferred feature of the invention, and additionally, the number of concentric rings in the accumulator may be modified. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention and many of the attendant advantages thereto will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a sectional diagrammatic view of the bow of a submarine showing a vehicle launch assembly including the ring diaphragm of the present invention in its resting position; 
     FIG. 2 is an enlarged top plan view of the ring diaphragm of the invention showing, among other features, the concentric rings and the central check valve shown in partial cutaway; 
     FIG. 3 is an enlarged cross-sectional view along lines  3 — 3  of the ring diaphragm shown in FIG. 2, depicting the ring diaphragm in its fully charged position; and 
     FIG. 4 is a view of the ring diaphragm shown in FIG. 3 depicting the ring diaphragm in its flow release position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown a diagrammatic view of the bow of a submarine, cut away to display an illustrative launch assembly in accordance with the present invention. 
     The outer hull  10  and the inner hull  12  of the bow define a free flood area  14  which is open to outside seawater through one or more openings  16  in the outer hull  10 . A pump  18  is provided within the inner hull and has a suction side, adapted to draw fluid from the free flood area  14 , and a discharge side to inject pressurized fluid into an impulse tank  20 . 
     Impulse tank  20  is defined by the submarine inner hull  12 , impulse tank walls  22  extending from inner hull  12 , and a ring diaphragm  24 . Ring diaphragm  24  is shown in FIG. 1 in its resting position. 
     Referring to FIG. 2, a top plan view of ring diaphragm  24  is shown. Outer base ring  30  supports the ring diaphragm and secures it to the walls  22  of impulse tank  20 . Radiating inward from the base ring  30  is a series of two elastomeric rings  32  and  34 , alternating with two rigid steel rings  36  and  38 . At the center of ring diaphragm  24  is central check valve  40  (shown in partial cutaway) with four flow release cutouts  42  and valve flaps  44 . The elastomeric rings  32  and  34  can be of neoprene, natural rubber, or the like. 
     Returning to FIG. 1, a launch tube  50  has a breach end  54  and a mouth  52  containing muzzle valve  53 . The launch tube  50  communicates with impulse tank  20  when a flow controlling slide valve  56  is moved to its open position. With the slide valve  56  closed, the impulse tank  20  can be charged. The submarine utilizes fluid in free flood area  14 , provided through an opening  16  in outer hull  10 . The fluid is drawn in by pump  18 , as indicated by the arrow  15 , so as to charge the impulse tank  20  and to cause the elastomeric rings  32  and  34  of ring diaphragm  24  to deform in shear strain. 
     Referring to FIG. 3, a sectional view of ring diaphragm  24  taken along  3 — 3  of FIG. 2 illustrate the ring diaphragm in its fully charged position. Increased pressure in the impulse tank  20  causes elastomeric rings  32  and  34  to deform in shear strain to accept the pressurized fluid being added. When pressure in impulse tank  20  exceeds pressure in free flood area  14 , check valve  40  is closed. Valve flaps  44  are seated against flow release cutouts  42 , preventing escape of fluid from the impulse tank  20 . The amount of displacement permitted by the elastomeric rings  32 ,  34  is controlled by the charged volume of the impulse tank  20 . The required potential fluid energy can be stored at below 50% shear strain. 
     Returning to FIG. 1, a fluid impulse can be delivered from the charged impulse tank  20  to launch tube  50  by opening slide valve  56 . This fluid impulse ejects launch vehicle  58  from the submarine. 
     As the impulse fluid is discharged, elastomeric rings  32  and  34  begin to return to the resting state. Referring to FIG. 4, a sectional view of ring diaphragm  24  in its flow release position is shown. Displacement stops  37  and  39 , which extend from impulse tank walls  22 , are positioned in the path of rings  36  and  38 . The displacement stops  37 ,  39  halt the motion of the deflating ring diaphragm  24 , preventing a reversal and maintaining a slight positive shear strain in the elastomeric rings  32  and  34  so that crystalline structures within the elastomer will resist crack propagation. Displacement stops  37  and  39  are constructed in a step-down configuration such that displacement stop  39  permits a slightly larger range of motion than does displacement stop  37 . 
     As further shown in FIG. 4, when rigid rings  36  and  38  contact displacement stops  37  and  39 , dashpot cavities  46  and  48  are created. The rigid rings  36  and  38  trap an amount of fluid within the cavities, causing a smooth and quiet arrest to rings  36  and  38  against stops  37  and  39 . 
     Returning again to FIG. 1, it is noted that the discharge of pressurized fluid from impulse tank  20  can create a pressure differential such that fluid pressure in the free flood area  14  is higher than that in launch tube  50  and impulse tank  20 . Without equilibration, noisy cavitation can occur on the surface of the ring diaphragm  24 . 
     As shown in FIG. 4, central check valve  40  is in its flow release position. Higher fluid pressure in free flood area  14  holds valve flaps  44  open, allowing fluid to enter the impulse tank  20  through cut-outs  42 , and flow toward the launch tube  50 . Thus, cavitation is prevented. The flow release feature also permits a smaller impulse fluid volume, because rapid deceleration of flow is avoided. This in turn results in shorter recharge times. The central location of the check valve has the advantage of providing a smoother flow through the system than a peripheral valve would permit. Additionally, the integrated valve/ring configuration of ring diaphragm  24  provides a mechanically simple ejection system. Once equilibration has occurred, impulse tank  20  is ready for recharging. 
     In light of the above, it is therefore understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.