Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Reexamination Certificate
1998-10-29
2001-02-20
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
C244S075100, C244S078200
Reexamination Certificate
active
06189837
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hydraulic systems that utilize pyrotechnic power, and more particularly, to hydraulic systems for which pyrotechnic-powered devices provide pressurization to retract spoilers during an emergency situation.
BACKGROUND OF THE INVENTION
For commercial aircraft, it is important in emergency situations to be able to quickly and effectively evacuate all passengers. In support of this, various aircraft components must be operable, even if the aircraft loses its ability to provide electrical and/or hydraulic power.
One example of where this is crucial is in the retraction of wing spoilers. During an emergency, overwing exit doors may be opened to provide passengers with an alternative escape route. It is typical for the opening of these doors to trigger automatic deployment of self-inflating overwing escape slides. Because these slides are puncturable, it is important to quickly retract any extended wing surfaces that may interfere with or damage the slides, or that may interfere with passenger egress. Should the aircraft lose its hydraulic and/or electrical systems, some type of backup system must be available to retract these surfaces.
FIG. 1
illustrates a known aircraft having an actuator
10
that is activated by a pyrotechnic device
12
. The opening of an overwing escape door triggers a battery to send a current to the pyrotechnic device and to an electrical relay that removes power from a hydraulic servo valve that is mechanically biased to the retract position with power off. The device, in turn, causes an actuator piston
14
to mechanically rotate a spoiler panel
16
to its stowed position. This system works satisfactorily, but has a number of implementation disadvantages. One disadvantage is that the actuator must be connected to wing structure that is capable of withstanding the actuator's reaction loads when fired. This requires an increase in the thickness of the wing loading members, which adds undesirable weight to the wing. A second disadvantage is that the spoiler surface must be designed to include a moment arm for the actuator to react against. This adds weight to the spoiler surface and makes the configuration no longer compatible with other variations of that particular airplane model. A third disadvantage is that the actuator must be mounted in a specific location to push against the spoiler surface.
A fourth disadvantage is that the actuator is not connected to the main hydraulic system. Therefore, the actuator must be checked periodically for leaks, and if leaks have occurred, they must be repaired and the actuator manually refilled with hydraulic fluid. In addition, once the actuator is fired, it must be manually repositioned to its initial state. Should an anomalous firing occur in flight, the actuator would apply a load to the spoiler surface until the gas pressure is manually released, on the ground.
U.S. Pat. No. 5,582,010 describes a pyrotechnically operated pressurization device attached directly to a hydraulic tank. The device is activated by an electronic igniting unit that heats a combustion chamber filled with a propellant charge. The expanding propellant charge activates a cartridge base to eventually force excess hydraulic fluid into the tank. Upon activating the device, the entire hydraulic tank and its corresponding circuits are pressurized. A disadvantage of this device is the possibility that the pressurization may be insufficient for the entire hydraulic system, plus any leaks or pressure outlets resulting from the emergency situation may thwart the pressurization provided by the pyrotechnic device.
Thus, a need exists for an auxiliary hydraulic power system capable of providing emergency hydraulic fluid pressurization to select aircraft components. Example components that would benefit from such a device are wing spoilers. An ideal auxiliary spoiler retract system would be capable of quickly retracting extended spoilers upon the opening of overwing exit doors and/or deployment of overwing emergency escape slides. The ideal auxiliary spoiler retract system would be pyrotechnically activated, would include components that do not require significant maintenance, and would have minimal impact on the aircraft's main hydraulic system. Activation of the system would provide immediate hydraulic pressure to the spoilers without necessarily having to provide pressure to the entire hydraulic system. Further, the ideal auxiliary hydraulic power system would be available regardless of the availability of the aircraft's main electrical and/or hydraulic systems. The present invention is directed to fulfilling these needs.
SUMMARY OF THE INVENTION
In accordance with aspects of the present invention, an improvement to an aircraft is provided for moving a particular hydraulically-operated aircraft component in a desired direction during an emergency situation. The improvement includes a transfer cylinder assembly for producing a discrete amount of pressurized hydraulic fluid. Means are provided for ensuring that the fluid enters the component at a location appropriate to force the component to move in the desired direction.
The transfer cylinder assembly includes a housing having a first compartment, a second compartment fillable with a hydraulic fluid, and a piston separating the first and second compartments. The second compartment includes an output port in hydraulic communication with the particular aircraft component. A cartridge is mounted on one end of the housing near the first compartment. The cartridge includes a main firing element. Activation of the cartridge causes the main firing element to produce expanding gas that enters the first compartment and forces the piston to translate, thus forcing hydraulic fluid out the output port.
The housing preferably includes a refill port adapted to connect to the aircraft's main hydraulic system return line. In one embodiment, an isolation check valve is in communication with the transfer cylinder assembly to allow hydraulic fluid to exit the second compartment through the output port while prohibiting the reverse flow. The transfer cylinder assembly cartridge is preferably activated by an electric current sent from a battery, so that the assembly need not rely on electrical power from the aircraft's main electrical system.
In accordance with other aspects of this invention, one embodiment of the improvement is described as applied to the retraction of a hydraulic spoiler. In this embodiment, a spoiler actuator having an extend and a retract side is connected to the return and pressure lines of the aircraft's main hydraulic system. The transfer cylinder assembly output port is in hydraulic communication with the retract side of the actuator. The second compartment includes a refill port adapted to connect to a hydraulic system return line. A check valve is located at the refill port for allowing entry of hydraulic fluid into the second compartment while prohibiting the reverse flow.
In accordance with still other aspects of this invention, a preferred transfer cylinder assembly is provided having a housing and a cartridge attached to the housing. The housing includes a first compartment, a second compartment fillable with a hydraulic fluid, and a piston separating the first and second compartments. The second compartment has an output port. The cartridge includes a main firing element. Activation of the cartridge causes the main firing element to produce expanding gas that enters the first compartment and directly forces the piston to translate, thus forcing hydraulic fluid out the output port.
In one embodiment, the cartridge includes an ignition device and a time delay component in addition to its main firing element. An example cartridge that may be used is the P/N S251W172 manufactured by OEA Aerospace, Inc. In one embodiment, the time delay component causes a delay of an amount in the range of about 0.26 to about 0.36 seconds. In another embodiment, the transfer cylinder assembly provides hydraulic fluid at a pressu
Barefoot Galen L.
Christensen O'Connor Johnson & Kindness PLLC
The Boeing Company
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