Abstract:
A pneumatically operated stores ejector rack for an aircraft having an adjustable flow restricting device for variably apportioning the flow of pressurized gas from a manifold to the store ejection thrusters. The flow restricting device includes at least one adjustable valve assembly, having a valve and a valve body, for varying the pressure of gas supplied to the thruster. It also includes a feed conduit connecting the manifold and the valve, and a collar threadably engageable with the manifold and the feed conduit for urging the valve into contact valve body. Also disclosed is a method for apportioning the flow of pressurized gas between a pair of thrusters in a stores ejection rack which includes the flow restricting device.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to store ejector racks for aircraft, and more particularly to apparatus and methods for variably restricting and apportioning pressurized fluid to one or more fluid actuated thrusters of an aircraft ejector rack system.  
       BACKGROUND OF THE INVENTION  
       [0002]     An aircraft ejector rack is a device used to carry and release stores such as bombs and missiles from an aircraft in flight. These racks are typically mounted to the undersurfaces of aircraft wings and fuselages and incorporate both release and ejection features. The release features normally include bails or hooks from which stores may be suspended, and the ejection features normally include pneumatically operated rams for forcibly ejecting stores away from the aircraft to minimize the possibility of their colliding with the aircraft after release.  
         [0003]     A contemporary ejection rack system of the type described above incorporates an onboard pressurization capability, employing a single pressurization system capable of operating multiple release mechanisms and uses air to operate both the store release bails and ejector rams. The system also includes a miniature compressor and a gas purification system which filters, dries, and stores ambient air as an energy medium. With the onboard compressor, pressure in the system can be maintained at the desired operating level regardless of system usage or temperature changes in the gas. The use of air eliminates the problems associated with the use of pyrotechnics to generate high pressure gasses, such as periodic cleaning required by the corrosives and moisture generated in such systems, and also eliminates the sealing problems commonly found in hydraulically operated ejector racks. An example of such a state-of-the-art pneumatically operated ejector rack system is seen in U.S. Pat. No. 5,583,312.  
         [0004]     It has also been found to be desirable to apply differential forces to a store upon release from an aircraft in order to impart a predetermined pitch rate to it. By doing so, the store can be directed upon a flight path which will carry it away from the aircraft so as to minimize the possibility of a store colliding with the aircraft after release. In prior pneumatic systems, such pitch rate control has been accomplished by varying the flow rate and pressure of the fluid supplied to the thrusters. Among the means employed to vary pressure among a group of thrusters have been replaceable orifices of varying cross sectional areas and adjustable orifices disposed in the manifolding between the pressure source and the thrusters. A typical example of an adjustable orifice is shown in U.S. Pat. No. 6,009,788, which will be described in greater detail below. A significant advantage of this particular variable orifice design is that it permits adjustment without disassembling of the ejector system and eliminates the necessity of maintaining an inventory of replaceable orifices. One problem that has been encountered with this system, however, is that in operation the variable orifices assembly tended to leak, making calibration of the device difficult.  
         [0005]     Accordingly, there is an unmet need in the art for a pneumatically operated ejector rack including a thruster actuation system having a plurality of improved adjustable flow restricting devices for supplying differential fluid pressure to the thrusters.  
       SUMMARY OF THE INVENTION  
       [0006]     This invention can be broadly summarized as providing for a stores ejector rack for an aircraft. In one particular embodiment, a rack includes at least one pneumatically operated thruster for ejecting a store away from the aircraft, and a manifold for distributing pressurized gas from a source such as a compressor to the thruster. Particularly, the rack includes an adjustable valve assembly, including first and second valve members, for varying the pressure of the gas supplied to the thruster. The rack also includes a feed conduit connected to the manifold and to one of the valve members and a collar engageable with the manifold and the feed conduit for urging the valve members into contact.  
         [0007]     In accordance with one embodiment of the invention, a collar is threadably engaged with the feed conduit and may be rotated into contact with the manifold. In accordance with a second embodiment of the invention, a collar is threadably engaged with the manifold and may be rotated into contact with the feed conduit. In accordance with a more detailed aspect of both embodiments of the invention, a fluid tight seal is disposed between the manifold and the feed conduit.  
         [0008]     This invention can also be broadly summarized as providing for a method of variably apportioning pressurized fluid flow between two pneumatically actuated thrusters of an aircraft stores ejector rack. The ejector rack includes a manifold, a pair of feed conduits, each of which is connected to the manifold, and a pair of thrusters. Each of the thrusters is in communication with a valve assembly connected to one of the feed conduits, and is adjustable in flow rate by rotation of the feed conduit. Also, a collar is threadably mounted for rotation on each of the feed conduits and is engageable with the manifold. The method includes introducing pressurized fluid from a source into the manifold, disengaging the collars from the manifold so that the feed conduits may be rotated, adjusting the valve assemblies is to obtain the desired apportionment of pressurized fluid between the thrusters, and tightening the collars against the manifold. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of an ejector rack constructed in accordance with an embodiment of the present invention;  
         [0010]      FIG. 2  is a side view of a portion of the ejector rack of  FIG. 1 ; and  
         [0011]      FIG. 3  is a partial side view, partially in a section, of the aft manifold conduit and an adjustable flow restricting device according to an embodiment of the present invention.  
         [0012]      FIG. 4  is a partial side view, partly in section of a second embodiment of the subject adjustable flow restricting device.  
         [0013]      FIG. 5  is a side view of an aircraft in accordance with another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     The present invention relates to apparatus and methods for separating stores from an aircraft. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1-5  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description.  
         [0015]     In  FIGS. 1 and 2  of those drawings, a pneumatic ejector rack assembly for forcibly ejecting a store from an aircraft in accordance with an embodiment of the present invention is illustrated and generally designated by the numeral  10 . Store  20  is suspended from the ejector rack assembly by carrier  22  which includes hook  24  and hook actuating mechanism  26 . The rack assembly also includes pneumatically actuated thrusters  30  and  32  which include rams  34  and  36 , each of which is disposed for reciprocating motion within its respective thruster. The purpose of the thruster is to forcibly eject store  20  downward and away from the aircraft simultaneously with release of the store by carrier  22  to minimize the possibility of the store striking the aircraft after release. Thrusters  30  and  32  are each mounted to aircraft structural portion  40  and are normally enclosed by cover  42  which has been displaced in  FIG. 1  for clarity. Store  20  is illustrated in  FIG. 1  just after release by carrier  22  at the point where rams  34  and  36  are fully extended. In contrast,  FIG. 2  shows the rams in their fully retracted position and with hook  24  in engagement with tongue  42  of carrier  22 . In this position store  20  is maintained in longitudinal and lateral alignment with respect to ejector rack assembly by alignment pin  44  which seats in hanger  45  as shown. Alignment is also maintained by rams  34  and  36  which are seated in sway braces  46  and  48 , respectively.  
         [0016]     Both the thrusters and the release mechanism are actuated by compressed air from a remotely located onboard pressurization unit (not shown) which supplies dry filtered and pressurized air to accumulator  50 . The accumulator  50  is in fluid communication with ejector rams  30  and  32  by means of manifold  52  and feed conduits  54  and  56 , respectively. The accumulator is likewise in fluid communication with release piston chamber  60 . Upon command, high pressure air is provided from the accumulator to hook release piston chamber  60 , driving hook release piston  62  downward, actuating release mechanism  26 . Hook  24  is then rotated counterclockwise (as seen in  FIG. 2 ) driving tongue  42  downward and releasing store  20 . Simultaneously, high pressure air is provided from the accumulator to ram chambers  70  and  72  (not shown) within ejector rams  30  and  32 , driving rams  34  and  36  downward and forcibly ejecting store  20  away from the aircraft. Ejector rack assemblies of the type generally described above are known in the prior art as exemplified by U.S. Pat. Nos. 5,583,312 and 6,035,759, which patents are incorporated herein by reference.  
         [0017]     It is also known to be desirable to differentially control the air pressure provided to thruster assemblies as described above in order to control the force imparted by each ram to the store. Such differential control permits adjustment of ejector rack for stores of varying mass and mass distribution. In connection with the present invention, apportionment of pressurized fluid to ejection rams  30  and  32  is accomplished by means of adjustable valve assemblies  80  and  82 , respectively, positioned between feed conduits  54  and  56  and the thrusters to which each is attached. It is understood that these valve assemblies are identical in construction, so only one will be described herein.  
         [0018]     Referring to  FIG. 3 , in this embodiment, fitting  84  is attached to feed conduit  86  of feed conduit  56 . Fitting  84  is slidably insertable in bore  88  of receiver  90 . O-ring  92  is positioned on fitting  84  as shown to provide a fluid tight seal between the fitting and the receiver. Accordingly, feed conduit  56  may be rotated about its centerline  94  and translated parallel to that center line without disturbing the seal between fitting  84  and receiver  90 . A circular opening  100  having a centerline  101  is formed in face  102  of fitting  84  and is positioned eccentrically with respect to centerline  94 . Fluid flowing through feed conduit  56  toward fitting  84  must exit the fitting through opening  100 . Similarly, circular opening  104  having a centerline  105  is formed in the base of bore  88  and also positioned eccentrically with respect to center line  94 . Fluid passing into the receiver through bore  88  must pass through opening  104  as it enters thruster  32 . Accordingly, it can be seen that when fitting  84  is seated in receiver  90  and rotated with respect to the receiver such that there is overlap between openings  100  and  104 , fluid may pass through feed conduit  56 , then through the orifice formed by overlapping openings  100  and  104  and through receiver  90  into thruster  32 . By rotating feed conduit  56  with respect to receiver  90 , the overlap between openings  100  and  104  can be varied, thus forming a variable area orifice which can be used to control fluid flow into thruster  32 . In order to fix the rotational position of feed conduit  56  with respect to fitting  90  (and therefore fix the area of the orifice formed by openings  100  and  104 ), pin  114  may be inserted into one of a plurality of detents such as detent  108  formed in face  110  of the fitting. Details of a similar valve arrangement can be found in U.S. Pat. No. 6,009,788, incorporated herein by reference.  
         [0019]     In operation, the nominal pressure of the compressed air passing through feed conduit  56  and into valve assembly  82  is approximately 6,000 PSI. As that fluid passes through the orifice and valve assembly  82  it may experience a significant reduction in pressure depending upon the selected cross-sectional area of the orifice, thus creating a significant pressure differential across the valve. It has been found, however, that a slight gap may develop between faces  102  and  106 , permitting fluid to flow into the area between, decelerating and rising in pressure as it does so. The resulting pressure differential tends to force face  102  of fitting  84  to separate further from face  106 , causing erratic performance of valve assembly  82 . In order to prevent such separation, threads  120  are formed on the external surface of feed conduit  56  and collar  122 , which is internally threaded to match threads  120 , is positioned thereon. When manifold  52 , feed conduit  56  and receiver  90  are assembled, the feed conduit is inserted sufficiently far into the manifold that o-ring  126  sealably engages inner wall  128  of the manifold and end  124  is disposed over recess  130  of the feed conduit. Then, in order to ensure that face  102  of fitting  84  and face  106  of receiver  90  remain firmly in engagement during operation, collar  122  is rotated into contact with face  124  of the manifold and tightened as desired. In order to adjust the rotational position of fitting  84  with respect to receiver  90 , the collar merely needs to be loosened sufficiently that pin  114  is disengaged from the detent and moved to the left, permitting it to be rotated to the desired position. After the feed conduit is repositioned the collar is again rotated in the contact with end  124  and tightened, re-engaging faces  102  and  106 .  
         [0020]      FIG. 4  illustrates a second embodiment of the present invention in which the collar has been mounted on the manifold rather than the feed conduit. In this embodiment, manifold  140  is sized to be insertable in feed conduit  142  with o-ring  144  providing sealing engagement with inner wall  146 . Collar  148  engages threads  150  formed on external surface  152  of the manifold. When manifold  140  is inserted sufficiently into the feed conduit that o-ring  144  seats on inner surface  146 , collar  148  can be rotated into contact with end  154 , urging faces  102  and  106  (not shown) into engagement.  
         [0021]     It will be appreciated that embodiments of apparatus and methods in accordance with the present invention may be employed on a wide variety of aerospace vehicles. For example,  FIG. 5  is a side view of an aircraft  500  in accordance with another alternate embodiment of the invention. In this embodiment, the aircraft  500  includes a fuselage  502 , a pair of wings  504 , and at least one engine  506 . The aircraft  500  further includes a pair of stores separation systems  510  in accordance with the present invention located on the lower surfaces of each of the wings  504 . In one particular embodiment, each of the systems  510  is of the type described above and shown in  FIGS. 1-4 . It will be appreciated that a variety of alternate embodiments of stores separation systems in accordance with the invention may be conceived. For example, in one alternate embodiment, a stores separation system  512  in accordance with the present invention may be operatively coupled to the fuselage  502  rather than to the wings  504  (e.g. to eject a bomb, missile, drop tank, payload, etc), or to any other suitable portion of the aircraft  500 .  
         [0022]     Furthermore, although the aircraft  500  shown in  FIG. 5  is representative of a well-known fighter aircraft, specifically, an F/A-18E Super Hornet manufactured by The Boeing Company, in alternate embodiments, virtually any other type or variety of military aircraft may be conceived that include apparatus and methods in accordance with the present invention. In alternate embodiments, for example, the aircraft may be a fighter aircraft, a rotary aircraft, a bomber aircraft, or any other suitable type of manned or unmanned aircraft, including those described, for example, in The Illustrated Encyclopedia of Military Aircraft by Enzo Angelucci, published by Book Sales Publishers, September 2001, and in Jane&#39;s All the World&#39;s Aircraft published by Jane&#39;s Information Group of Coulsdon, Surrey, United Kingdom, which texts are incorporated herein by reference.  
         [0023]     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.