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CASCADED PNEUMATIC IMPULSE
SEPARATION SYSTEM AND VALVES THEREFOR
CROSS-REFERENCE TO RELATED 5
This application is a continuation-in-part of application U.S. Ser. No. 07/240/030 filed Sept. 2, 1988 entitled Pneumatic Impulse Valve and Separation System, no U.S. Pat. No. 4,878,647 the disclosure of which is 10 herein incorporated by reference.
FIELD OF THE INVENTION
This invention relates to a fluid impulse separation system and pneumatic impulse valves therefor. More 15 particularly, this invention pertains to an extremely rapid acting valve, or a series of valves, each capable of delivering an impulse of compressible fluid and to a fluid impulse separation system suitable for deicing of aircraft leading edge surfaces. 20
BACKGROUND OF THE INVENTION
From the beginning of powered aviation, aircraft have been under certain flying conditions troubled by accumulations of ice on component surfaces of aircraft 25 such as wings and struts. If unchecked, such accumulations can eventually so laden the aircraft with additional weight and so alter the airfoil configuration of the wings and control surfaces of that aircraft so as to precipitate an unflyable condition. Efforts to prevent and- 30 /or remove such accumulations of ice under flying conditions has resulted in three generally universal approaches to removal of accumulated ice, a process known generally as de-icing.
In one form of de-icing known as thermal de-icing, 35 leading edges, are heated to loosen adhesive forces between accumulating ice and the aircraft component. "Leading edges" as used herein means those edges of an aircraft component on which ice accretes and are impinged upon by air flowing over the aircraft and having 40 a point or line at which this airflow stagnates. Once loosened, this ice is generally blown from the aircraft component by the airstream passing over the aircraft. There are two popular methods of heating leading edges. In one approach known as electrothermal de- 45 icing, an electrical heating element is placed in the leading edge zone of the aircraft component, either by inclusion in a elastomeric boot applied over the leading edge, or by incorporation into the skin structure of the aircraft component. This heating element is typically pow- 50 ered by electrical energy derived from a generating source driven by one or more of the aircraft engines and is switched on and off to provide heat sufficient to loosen accumulating ice. In small aircraft, a sufficient quantity of electrical power may be unavailable for use 55 of electrothermal de-icing.
In the other heating approach, gases at elevated temperature from one or more compression stages of a turbine engine are circulated through the leading edges of components such as wings and struts in order to 60 affect a de-icing or anti-icing effect. This approach is employed typically only in aircraft powered by turbine engines by draining off compressed air having an elevated temperature from one or more compressor stations of a turbine engine. This approach can result in 65 reduced fuel economy and lower turbine power output.
The second commonly employed method for deicing involves chemicals. In limited situations, a chemi
cal has been applied to all or part of an aircraft to depress adhesion forces associated with ice accumulation upon the aircraft or to depress the freezing point of water collecting upon surfaces of the aircraft.
The remaining commonly employed method for deicing is typically termed mechanical de-icing. In the principal commercial mechanical de-icing means, pneumatic de-icing, the leading edge zone or wing or strut component of an aircraft is covered with a plurality of expandable, generally tube-like structures, inflatable employing a pressurized fluid, typically air. Upon inflation, the tubular structures tend to expand substantially the leading edge profile of the wing or strut and crack ice accumulating thereon for dispersal into the airstream passing over the aircraft component. Typically, these tube-like structures have been configured to extend substantially parallel to the leading edge of the aircraft. These conventional low pressure pneumatic de-icers are formed from compounds having rubbery or substantially elastic properties. Typically, the material forming the inflatable tubes on such de-icer structures can expand or stretch by 40% or more during an inflatable cycle, thereby causing a substantial change in the profile the de-icer as well as in the leading edge to thereby crack ice accumulating on the leading edge. These conventional pneumatic de-icers require a large volume of air to inflate their highly expandable tubes and the time for inflating such tubes typically and historically has averaged from about two and six seconds. The distortion of the airfoil profile caused by inflation of the tubes can substantially alter the airflow pattern over the airfoil and adversely affect the lift characteristics of the airfoil. The rubber or rubber-like materials forming these conventional pneumatic de-icers typically are possessed of a Young's modulus (modulus of elasticity) of approximately 6900 Kpa. The modulus of elasticity of ice is variously reported as being between about 275,000 Kpa and about 3,450,000 Kpa. Ice is known to be possessed of an elastic modulus enabling typical ice accumulations to adjust to minor changes in contours of surfaces supporting such ice accumulations. While the modulus of elasticity of rubber compounds used in conventional de-icers is much lower than the modulus of elasticity typically associated with ice accumulations. The large expansion of conventional pneumatic de-icers has functioned to crack or rupture the structure of the ice accumulations thereby allowing such accumulations to be swept away by impinging windstreams.
Other mechanical means for effecting ice de-icing include electromechanical hammering such as that described in U.S. Pat. No. 3,549,964 to Levin et al. Concern respecting the susceptibility of the airfoil skin to stress fatigue upon being hammered over extended periods of time have functioned in part to preclude substantial commercial development or adoption of such technique.
Another electromechanical ice removal system is described in U.S. Pat. No. 4,690,353 to Haslim et al. One or more overlapped flexible ribbon conductors, each of which is folded back on itself, is embedded in an elastomeric material. When a large current pulse is fed to the conductor, the anti-parallel currents in the opposed segments of adjacent layers of the conductor result in interacting magnetic fields producing an electrorepulsive force between the overlapping conductor segments causing them to be separated near instantaneously. This
distention tends to remove any solid body on the surface of the elastomeric material.
U.S. Pat. Nos. 4,706,911 to Briscoe et al and 4,747,575 to Putt et al disclose apparatus for de-icing leading edges in which an impulse of fluid under pressure is 5 utilized to rapidly inflate an inflation tube positioned between a support surface and a sheet-like skin possessed of a substantially elevated modulus. The impulse of fluid is delivered to the inflation tube causing the high modulus skin to dislocate and then stop suddenly. 10 Momentum imparted to the ice accumulations thereby causes additional ice movement which assists in ice detachment and dislodgement. The inflatable tubular structure in certain preferred embodiments is inflated within not more than about 0.1 second and preferably 15 not more than about 0.5 milliseconds. FIG. 4 and the attendant description of U.S. Pat. No. 4,706,911 describe an ejector/pilot operated discharge valve suitable for use in such pneumatic impulse de-icers. In FIG. 7 and the attendant description of U.S. Pat. No. 20 4,747,575 there is described a chattering valve for use in a pneumatic impulse de-icer which delivers a rapid series of fluid pressure pulses to the inflatable tube of a de-icer apparatus affixed to a leading edge. Efforts to improve such pneumatic impulse de-icing systems have 25 led to continuing efforts to improve valves for delivery of the desired fluid impulse.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there 30 is provided a valve comprising pilot, and output sections, the pilot section including a pilot housing containing a pilot cavity, inlet conduit means extending from the exterior of the pilot housing to the pilot cavity, exhaust conduit means extending from the pilot cavity 35 to the exterior of the pilot housing, and intermediate conduit means extending from the pilot cavity to said output section, gate means configured for movement from a load position during which the inlet conduit means is in fluid communication with said intermediate 40 conduit means and a dump position during which the exhaust conduit means is in fluid communication with said intermediate conduit means while said inlet conduit means is disconnected from said intermediate conduit means; and 45
the output section including an output housing containing an intermediate cavity having an inlet port in fluid communication with said intermediate conduit means, an exhaust vent, and an outlet port in fluid communication with output conduit means and accumula- 50 tion means, the outlet port being proximate to the exhaust vent, and a poppet contained within said intermediate cavity configured for movement from a load position during which fluid under pressure may enter the intermediate cavity and force the poppet to seal off 55 movement of fluid into the exhaust vent while permitting flow of fluid to the outlet port and a dump position during which fluid under pressure may flow from said accumulation means through said output conduit means to said vent. 60
According to another aspect of the invention, there is provided a valve comprising pilot and output sections, the pilot section including a pilot housing containing a pilot cavity, inlet conduit means extending from the exterior of the pilot housing to the pilot cavity, interme- 65 diate exhaust conduit means extending from the pilot cavity to the exterior of the pilot housing, a pilot piston reciprocably mounted within the pilot cavity and opera
bly connected to gate means configured for movement between a load position during which the output section is sealed off from fluid communication with said intermediate exhaust conduit means and an outlet associated with said output section and a dump position during which said output section is in fluid communication with said intermediate exhaust conduit means and said outlet;
the output section including an output housing containing an output cavity having an inlet orifice, an outlet and accumulation means, said outlet being sealed against fluid communication with said output cavity when said gate means is in load position and in fluid communication with said output cavity when said gate means is in dump position, and an output poppet reciprocably contained within said output cavity configured for movement from a load position during which fluid under pressure may enter the output cavity and force the poppet to seal off movement of fluid into the outlet while permitting flow of fluid into the accumulation means, and a dump position during which fluid under pressure may flow from said accumulation means to said outlet, said accumulation means opening to said output cavity proximate to said outlet.
In preferred embodiments, the poppet and associated output cavity are of cylindrical shape and the end of the poppet facing the exhaust vent includes a frustoconical face capable of sealing against flow from the intermediate cavity when engaged with the poppet seat. The inclusion of this frustoconical sealing face serves to accelerate the opening of the valve because as pressure is released from the output cavity and the poppet respectively begins to move away from its corresponding annular seat, a greater area is presented to the escaping fluid causing an even greater force to be exerted on the poppet moving it even more rapidly away from its seated position.
In preferred embodiments, the housing is unitary and is formed of metal, and the poppet piston is of plastic material.'
According to a further aspect of the invention, there is provided in combination a valve as aforedescribed and a fluid impulse separation apparatus which includes an outer surface layer formed of a material having a Young's modulus of at least 40,000 Kpa and at least one inflatable tubular member beneath the outer surface layer positioned such that fluid impulse inflation of the tubular member causes reaction movement of the outer surface layer to effect separation and dislodgement of any material lying thereon such as ice. In certain preferred embodiments, the outer surface layer is formed of a material having a Young's modulus of at least 275,000 kPa. In certain preferred embodiments, the outer surface layer is formed of metal selected from titanium and its alloys, aluminum and its alloys, magnesium and its alloys and stainless steels.
According to a further aspect of the invention, there is provided in combination a master valve comprising pilot and output sections, one or more slave valves each comprising pilot and output sections, and one or more fluid impulse separation apparatus(es). A fluid output of the master valve is operably connected by conduit means to the pilot section of one or more slave valves whereby initiation of dumping of the master valve initiates dumping of the slave valves. Other fluid outputs of the master and/or slave valves are operably connected by conduit means to fluid impulse separation apparatus. The valves and conduit means may be arranged to pro