Aeronautics and astronautics – Aircraft structure – Passenger or cargo loading or discharging
Reexamination Certificate
2000-05-24
2002-11-19
Jordan, Charles T. (Department: 3641)
Aeronautics and astronautics
Aircraft structure
Passenger or cargo loading or discharging
C089S001540
Reexamination Certificate
active
06481669
ABSTRACT:
This invention relates to a pneumatic actuator which is suitable for any high speed and/or high force applications and more particularly although not exclusively, to a pneumatic actuator for a stores carriage and ejection system which is operable to carry stores such as an airborne weapon or missile, on an aircraft in flight and to eject those stores from the aircraft on demand.
U.S. Pat. No. 5,932,829 discloses a missile storage and ejector rack assembly which is to be used with a pneumatic release and ejection system of the type described in the U.S. Pat. Nos. 5,583,312 and 5,857,647. U.S. Pat. No. 5,904,323 discloses a missile store release system which can be used with any suitable pneumatic, hydraulic or pyrotechnic ejection mechanism. GB-A-2,078,912 discloses a missile launcher having fore and aft ejection rams and pyrotechnic ejection cartridges which are fired simultaneously to generate hot gas which is fed to the rams to extend them on ejection of the missile. Use of pneumatics results in a better facility for controlling the pressure that acts to extend the ejector rams than is the case with pyrotechnic cartridges. This leads to an ability to charge different rams of a multi-ram ejector system to different pressures which is advantageous.
An object of this invention is to provide a pneumatic actuator which is simple, compact and efficient and which when used in an airborne weapon carriage and ejection system has a performance which compares more favourably with pyrotechnic systems than do conventional pneumatic systems.
According to one aspect of this invention there is provided a pneumatic actuator for a stores carriage and ejection system which is operable to carry the stores on an aircraft in flight and to eject those stores from the aircraft on demand, the actuator having an actuating member which includes an actuating rod portion which extends from a differential area piston having two piston portions, the cross-sectional areas of which are different, the differential area piston being slidable in a closed chamber which is filled with gas under pressure when the actuator is operated and from which the actuating rod portion projects, one of the piston portions being slidably engageable in a cavity which is formed in an end wall of the closed chamber and which has a cross-section similar to that of said one piston portion, there being means operable when said one piston portion is engaged in said cavity to apply gas under pressure to a surface of said one piston portion which is formed at an end thereof remote from the other piston portion whereby to apply an actuating thrust to the actuating member and to displace said piston portion from the cavity so that the greater cross-sectional area of the differential area piston is subjected to the gas under pressure within the closed chamber.
In a preferred embodiment releasable hold back means operable to hold the piston in the location that is furthest from the location of the piston at which the volume within the chamber is at its maximum are provided.
Hence initial movement of the piston (once the piston has been released when any releasable retaining means or said releasable hold back means are provided) will be effected under a low force until said one piston portion has been urged out of said cavity, such displacement of the piston allowing the largest possible force to be exerted on the piston by the action of compressed gas and the transfer of the greater possible portion of the expansion energy of compressed gas in the chamber to any load connected to the piston.
In a preferred embodiment the chamber is a cylinder which is closed at one end and is separated by a wall from another chamber which is charged with compressed gas in use of the actuator, the wall forms an aperture which serves as said cavity, the two piston portions form a stepped piston, and the actuating rod portion is a piston rod, the stepped piston being mounted at one end of the piston rod by the one of the two piston portions that has the smaller cross-sectional area, wherein the piston rod extends through the aperture and the other chamber and has a cross-sectional area which is smaller than that of the aperture which is sized to slidably receive said one piston portion of the stepped piston, the releasable hold back means being operable to hold the piston adjacent to the wall with said one piston portion received in the aperture.
Preferably the dimensions of the piston rod and the aperture allow substantially unrestricted gas flow between the other chamber and the cylinder when said one portion of the piston is displaced from the aperture towards the closed end of the cylinder. Valve means may be provided which are operable to place both sides of the piston in communication one with the other for a return stroke of the piston when the piston has been driven to the closed end of the cylinder by the action of compressed gas in the other chamber. The valve means may comprise a bi-stable shuttle valve which is switched from one of its states to the other by arrival of the piston at either end of the cylinder.
The releasable hold back means conveniently include an external latch. The latch may include a pivoted arm having an arcuate end portion which functions in the manner of a zero lift cam, the arm being adapted to be positioned so that the end portion abuts an abutment carried by a member which is coupled to the piston whereby to hold the piston in said location, the piston being released by displacement of the arm so that the end portion is moved to one side of the abutment, whereby the abutment is free for movement with the piston. Means operable to displace the arm may be provided, those means together with the arm being dynamically balanced. The external latch may include a collapsible pair of under-centre strut links which are coupled with the piston, which are held by the latch in stable equilibrium against the action of compressed gas on the piston and which are arranged to collapse and allow movement of the piston when the latch is released.
According to another aspect of this invention, there is provided a stores carriage and ejection system which is operable to carry stores on an aircraft in flight and to eject those stores from the aircraft in flight on demand, said system including at least one fluid pressure operable ejection ram which includes a piston which is slidably mounted in a cylinder, and compressed gas storage means adapted to supply compressed gas as the working fluid for operating said at least one ejection ram to eject the stores from the aircraft, wherein the interior of the cylinder of the or each said at least one ejection ram serves as said compressed gas storage means.
In such a stores carriage and ejection system which includes at least two fluid pressure operable ejection rams, the cylinders of the ejection rams may be charged to different pressures for ejecting the stores as may be required when the center of gravity of the stores is not equally spaced from each ram piston.
Preferably the piston of said at least one ejection ram is a differential area piston having two piston portions, the cross-sectional areas of which are different, and an actuating rod portion which projects substantially co-axially with the two piston portions out of the cylinder which is a closed chamber which is filled with gas under pressure when the ejection ram is operated, the one of the piston portions that has the larger cross-sectional area being slidably engagable in a cavity which is formed in an end wall of the closed chamber and which has a cross-section similar to that of said one piston portion so that the piston is urged towards said end wall by the gas pressure loading thereon when said one piston portion is engaged in said cavity and said closed chamber is filled with gas under pressure, said end wall being remote from a location in the closed chamber from which the actuating rod portion projects out of the closed chamber, there being means operable to apply gas under pressure to a surface of said one piston portion whe
Dinh T.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Flight Refuelling Limited
Jordan Charles T.
LandOfFree
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