Abstract:
A deicer is provided for breaking up and removing accumulated ice on an airfoil surface. The deicer includes a bondside surface that is bonded to the airfoil surface, a breezeside surface on which the ice will accumulate, and passage-defining surfaces therebetween. The passage-defining surfaces define a plurality of expansible and contractible inflation passages and include a moisture-impervious coating whereby moisture within the inflation passages will not be absorbed by the surfaces. The bondside, breezeside and passage-defining surfaces may be contained on a deicer panel and means may be provided for introducing inflation fluid to and evacuating inflation fluid from the passages to expand and contract the inflation passages to break up and remove the accumulated ice.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/226,186 filed on Aug. 18, 2000. The entire disclosure of this provisional application is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally as indicated to aircraft deicing equipment and, more particularly, to a pneumatic deicer wherein the surfaces defining inflation passages are appropriately coated to deter undesired moisture absorption. 
     BACKGROUND OF THE INVENTION 
     An aircraft may be periodically exposed to conditions of precipitation and low temperatures which may cause the forming of ice on the leading edges of its wings and/or on other airfoils during flight. If the aircraft is to perform sufficiently in flight, it is important that this ice be removed. To this end, various types of aircraft deicers have been developed to address this issue. An aircraft deicer is designed to break up ice accumulations which undesirably tend to form on certain airfoils (such as the leading edges of the aircraft&#39;s wings) when the aircraft is operating in severe climatic conditions. 
     Of particular interest to the present invention is pneumatic aircraft deicers. A pneumatic deicer typically comprises a deicing panel that is installed on the surface to be protected, such as the leading edge of an aircraft wing. One surface of the deicing panel is adhesively bonded to the wing and this surface is referred to as the “bondside” surface. The other surface of the deicing panel is exposed to the atmosphere and this surface is referred to as the “breezeside” surface. For sake of directional clarity, the terms “bondside” and “breezeside” may be used to refer to the location of respective surfaces of the deicer and its components relative to the wing. Specifically, a bondside surface would be the surface relatively closest to the wing and a breezeside surface would be the surface relatively most removed from the wing. 
     The panel of a pneumatic deicer also includes inner surfaces which define inflatable passages. An inflation fluid, such as air, is repeatedly alternately introduced and evacuated from the passages via tubes or other suitable connection means during operation of the deicer. The cyclic inflation and deflation of the passages causes a change in the bondside surface geometry and surface area thereby imposing shear stresses and fracture stresses upon the sheet of ice. The shear stresses displace the boundary layer of the sheet of ice from the deicer&#39;s breezeside surface and the fracture stresses break the ice sheet into small pieces which may be swept away by the airstream that passes over the aircraft wing. 
     A pneumatic deicer will typically be constructed from a plurality of layers including two passage-defining layers which define the inflation passages. These passage-defining layers are commonly viewed as the carcass of the deicer and/or the deicer panel. One of the passage-defining layers is usually non-deformable and includes a breezeside surface which is a passage-defining surface. The other of the passage-defining layers is deformable and includes a bondside surface which is a passage-defining surface. When the passages are inflated, the passage-defining surfaces are in contact with the inflation fluid. 
     The carcass layers typically each comprise a fabric ply coated on one side with rubber or another similar coating. For example, the non-deformable layer may comprise a square-woven fabric while the deformable layer may comprise a knit fabric. The carcass is manufactured by sewing the coated fabric layers together with the uncoated fabric surfaces facing each other. Thus, the uncoated fabric surfaces will form the passage-defining surfaces of the deicer. 
     When the passages are deflated and/or are being deflated, the texture of the uncoated fabric surfaces prevents flow-precluding contact between these surfaces as the inflation fluid is being evacuated from the passages. In other words, the texture of the fabric prevents the entrapment of inflation fluid. Thus, the texture of the uncoated fabric has conventionally been viewed as allowing the air to pass more freely through the carcass during deflation thereby allowing the deicer to “breathe.” 
     When the passages are inflated or are being inflated, the uncoated fabric surfaces are in contact with the inflation fluid (e.g., air) and the coating on the opposite fabric surfaces prevent the escape of inflation fluid from the passages. Accordingly, the adhesion between the coating and the fabric is a significant factor in deicer operability. For this reason, the fabric plies are often treated with an RFL (resorcinol-formaldehyde-latex) dip prior to application of the coating to promote adhesion between the fabric and its coating. 
     The inventors appreciated that moisture may be present in the inflation fluid whereby water is introduced into the inflation passages during operation of the deicer. The inventors additionally appreciated that moisture absorbed through the uncoated fabric surfaces of the carcass layers may cause a weakening, or even a failure, of the adhesive bond between the fabric and the rubber coating thereby reducing the useful life of the deicer. While an RFL dip may serve to promote adhesion between the fabric and its coating, the strength of adhesion may be reduced by the presence of liquid water, particularly at warmer temperatures. 
     SUMMARY OF THE INVENTION 
     The present invention provides a deicer for an aircraft wherein the passage-defining surfaces are coated with a water impervious coating to prevent the absorption of moisture through the fabric plies of the carcass layers. 
     More particularly, the present invention provides a deicer for breaking up and removing accumulated ice on an airfoil surface. The deicer comprises a bondside surface which is bonded to the airfoil surface, a breezeside surface on which the ice will accumulate, and passage-defining surfaces therebetween. The passage-defining surfaces define a plurality of expansible and contractible inflation passages and include a moisture-impervious coating. The deicer may comprise a deicer panel (which includes the bondside surface, the breezeside surface and the passage-defining surfaces) and means for introducing inflation fluid to and evacuating inflation fluid from the passages. Thus, when the deicer is bonded to an airfoil surface of an aircraft (such as the leading edge of a wing), the expansion and contraction of the inflation passages will break up and remove the accumulated ice. 
     The deicer panel may comprise a carcass which includes the passage-defining surfaces, such as a carcass formed from a first layer and a second layer which are joined together to form the inflation passages. The first layer may comprise a first fabric ply (such as RFL treated nylon square woven fabric) and the moisture-impervious coating (such as natural rubber) would be on the breezeside surface of the first fabric ply. The second layer may comprise a second fabric ply (such as a RFL treated nylon knit fabric) and the moisture-impervious coating (such as rubber) would be on the bondside surface of the second fabric ply. The coating on the breezeside of the first fabric ply and/or the coating on the bondside of the second fabric ply may be texturized. Additionally or alternatively, the bondside surface of the first fabric ply may also be coated with a moisture-impervious coating and/or the breezeside surface of the second fabric ply may also be coated with a moisture-impervious coating. 
     These and other features of the invention are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative of but one of the various ways in which the principles of the invention may be employed. 
    
    
     DRAWINGS 
     FIG. 1 is a schematic perspective view of a deicer according the present invention, the deicer being shown secured to the leading edge of an aircraft wing. 
     FIG. 2 is an enlarged perspective view of the deicer as shown in FIG. 1 with certain parts broken away. 
     FIGS. 3A and 3B are schematic views of the deicer panel in a deflated state and an inflated state, respectively. 
     FIG. 4 is an enlarged sectional view of the carcass of the deicer panel. 
     FIG. 5 is an enlarged plan view showing the texture of an inner surface of the carcass. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and initially to FIG. 1, a deicer  10  according to the present invention is shown installed on an aircraft  12 . More particulary, the deicer  10  is shown installed on each of the leading edges  16  of the wings  14  of the aircraft  12 . The deicer  10  breaks up ice accumulations which undesirably tend to form on the leading edges  16  of the aircraft wings  14  under severe climatic flying conditions. 
     Referring additionally to FIG. 2, the deicer  10  is shown in more detail. The deicer  10  includes a deicing panel  20  that is installed on the surface to be protected which, in the illustrated embodiment, is the leading edge  16  of the wing  14 . One surface of the deicing panel  20 , the bondside surface  22 , is adhesively bonded to the wing  14 . The other surface of the deicing panel  20 , the breezeside surface  24 , is exposed to the atmosphere. During operation of the aircraft  12  in severe climate conditions, atmospheric ice will accumulate on the deicer&#39;s breezeside surface  24 . 
     The panel  20  also includes inner surfaces  26  and  28  which define inflatable passages  30 . An inflation fluid (such as air) is introduced and evacuated from the passages  30  via tubes or other suitable connection means  32 . In the illustrated embodiment, each of the inflatable passages  30  has a tube-like shape extending in a curved path parallel to the leading edge of the aircraft wing  12 . The illustrated inflatable passages  30  are arranged in a spanwise succession and are spaced in a chordwise manner. 
     Referring further to FIGS. 3A and 3B, the passages  30  are shown in a deflated state and an inflated state, respectively. When the passages  30  are in a deflated state, the breezeside surface  24  of the deicer panel  20  has a smooth profile conforming to the desired airfoil shape and ice accumulates thereon in a sheet-like form. Also, the passage-defining surfaces  26  and  28  are positioned flush and parallel with each other and may contact each other. (FIG. 3A.) When the passages  30  are in an inflated state, the breezeside surface  24  and the passage-defining surface  28  take on a bumpy profile with a series of parabolic-shaped hills corresponding to the placement of the passages  30 . (FIG. 3B.) 
     The change of surface geometry and surface area that results from the inflation/deflation of the passages  30  imposes shear stresses and fracture stresses upon the sheet of ice. The shear stresses displace the boundary layer of the sheet of ice from the deicer&#39;s breezeside surface  24  and the fracture stresses break the ice sheet into small pieces which may be swept away by the airstream passing over the aircraft wing  14  during flight. (FIG. 3B.) It may be noted for future reference that the bondside surface  22  and the passage-defining surface  26  do not change shape or profile during inflation/deflation of the passages  30 . 
     The deicer panel  20  is formed from a plurality of layers or plies  40 ,  42 ,  44 ,  46 , and  48 . The layer  40  is positioned closest to the aircraft wing  12  and its wing-adjacent surface forms the bondside surface  22  of the deicer panel  20 . The layer  42  is positioned adjacent the layer  40  and the layer  44  is positioned adjacent the layer  42 . The facing surfaces of the layers  42  and  44  define the passage-defining surfaces  26  and  28 , respectively, of the deicer panel  20 . The layer  46  is positioned adjacent the layer  44 . The layer  48  is positioned adjacent the layer  46  and is farthest from the aircraft wing  12  whereby its exposed surface forms the breezeside surface  24  of the deicer panel  20 . During inflation/deflation of the passages  30 , the layers  40  and  42  maintain substantially the same smooth shape while the layers  44 ,  46 , and  48  transform between a smooth shape and the bumpy profile shown in FIG.  3 B. 
     The non-deformable layer  40  provides a suitable bondside surface  22  for attachment to the aircraft wing  14  and may comprise Neoprene. As is explained in more detail below, the non-deformable layer  42  and the deformable layer  44  may comprise coated fabric sheets sewn together in a pattern which establishes the passages  30 . The deformable layer  46  is provided to facilitate the return of the other deformable layers  44  and  48  to the flush deflated position and may comprise natural rubber. The deformable layer  48  may be made of a material which is resilient and extensible to allow the required expansion/contraction, which enhances the weather resistant properties of the deicer, and which provides a more aesthetically pleasing appearance. A suitable material for the layer  48  would be Neoprene or polyurethane. Securement of the various deicer layers together and to the leading edge of the aircraft may be accomplished by cements or other bonding agents compatible with the materials employed. 
     Referring now to FIG. 4, the passage-defining layers  42  and  44  are shown in more detail. The layers  42  and  44  are commonly viewed as the carcass  50  of the deicer  10  and/or the deicer panel  20 . During the manufacture of a deicer panel, the carcass  50  is usually initially made and tested, and then the other layers of the panel  20  (such as layers  40 ,  46  and  48 ) are assembled to the carcass  50 . Specifically, for example, the layers  42  and  44  are sewn together with stitches  52  to establish the desired inflation passages  30 . During subsequent assembly steps in the manufacture of the deicer panel, the assembled layers may be subjected to a final cure. The carcass  50  may be precured during its subassembly to prevent the passage-defining passages from sticking together during the final cure. 
     The layer  42  includes a bondside surface which is the bondside surface  60  of the carcass  50  and a breezeside surface which is the passage-defining surface  26 . The layer  44  includes a bondside surface which is the passage-defining surface  28  and a breezeside surface which is the breezeside surface  62  of the carcass  50 . When the passages  30  are inflated, the surfaces  26  and  28  are in contact with the inflation fluid and when the passages  30  are deflated, the surfaces  26  and  28  are in contact with each other. 
     The layer  42  comprises a fabric ply  70  and coatings  72  and  74  on opposite sides thereof. The fabric ply  70  may comprise a RFL treated square-woven nylon fabric and the coatings  72  and  74  may comprise a suitable rubber. The layer  44  comprises a fabric ply  80  and coatings  82  and  84  on opposite sides thereof. The fabric ply  80  may comprise a RFL treated knit nylon fabric and the coatings  82  and  84  may comprise a suitable rubber. Coatings may be applied to both sides of the fabrics  70  and  80  with suitable coating and/or lamination procedures. This coating and/or lamination may be done prior to formation of the passages  30  and/or prior to a carcass pre-curing steps. Double-sided coatings may instead be accomplished by using a low viscosity coating on side of the fabric ply  70 / 80  which strikes through and coats the opposite side of the fabric ply during the pre-cure of the carcass  50  or the final cure of the deicer panel  20 . 
     The coatings  74  and  84  form the passage-defining surfaces  26  and  28 , respectively, of the illustrated deicer  10 . When the passages  30  are inflated, the coatings  74  and  84  are in contact with the inflation fluid and when the passages  30  are deflated, the coating  74  and  84  are in contact with each other. In this manner, when moisture is introduced into the passages  30  during inflation, this moisture will not be absorbed by the fabric ply  70  and/or the fabric ply  80  and thus will not permeate through these layers. This protection against moisture absorption is believed to prolong the service life of the deicer  10 . 
     The coating  74  and/or the coating  84  may be texturized during assembly of the carcass  50  to provide the texture surface shown in FIG.  5 . For example, a texturized peel ply could be provided during a carcass pre-curing step and then removed thereafter. In any event, by texturizing the coating  74  and/or the coating  84 , flow-precluding contact between the passage defining surfaces  26  and  28  maybe prevented during deflation thereby minimizing the entrapment of inflation fluid. Thus, with appropriate texturing, the deicer  10  will “breathe” in the same manner as deicers having non-coated fabric passage-defining surfaces. 
     In the illustrated embodiment of the invention, both of the passage-defining surfaces  26  and  28  are coated with the moisture-impervious coating  74  and  84 . However, in certain situations, coating only one of these surfaces may provide sufficient protection from moisture and enhance deicer life. For example, if moisture-induced damage is found to occur primarily on the bondside of the carcass  50  in a particular deicer design, coating the surface  28  but not the surface  26  may be sufficient. Likewise, if moisture-induce damage is found to occur primarily on the breezeside of the carcass  50  in a particular deicer design, coating the surface  26 , but not the surface  28  may be sufficient. 
     By way of a particular example, the layer  40  may be 15 mil of a neoprene compound, the layer  42  may be 0.008 mil nylon square woven fabric coated on both sides with a natural rubber so that the coated fabric is approximately 0.013 mil, layer  44  may be 0.008 mil nylon knit fabric coated on both sides with a natural rubber so that the coated fabric is approximately 0.013 mil, layer  46  may be 20 mil natural rubber compound and layer  48  may be 15 mil of a neoprene compound. 
     One may now appreciate the present invention provides a deicer  10  which is protected against moisture-induced damage by moisture-impervious coatings  74  and  84  forming its passage-defining surfaces  26  and  28 . Although the invention has been shown and described with respect to a certain preferred embodiment, it is obvious that equivalent and obvious alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such alterations and modifications and is limited only by the scope of the following claims.