US 2438693 A
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March 30, 1948. R. G. CAMPBELL IICE REMOVING COVERING FOR AIRFOILS Filed March 17, 1944 2 sheets-sheet 1 MarCh 30, 1.948.- R Q CAMPBELL ICE REMOVING COVERING FOR AIRFOIL 2 shets-sneet z Filed March 17, 1944 Patented Mar. 30, 1948 UNITED STATES TENT OFFICE ICE REMOVING COVERING FOR AIRFOILS Application March 17, 1944, Serial No. 526,866
6 Claims. 1
` This invention relates to protective coverings or apparatus for airfoil-s and especially to inflatable coverings for preventing the accumulation of ice on the leading edge of such airfoils.
Objects of the invention are to provide effectively for breaking and removing ice formations on the leading edge of an airfoil; to provide for moving laterally pieces of broken ice into the ambient airstream for removal by the latter; to provide for expanding a protective covering or apparatus along an element thereof extending diagonally across the leading edge; to provide for local expansion of such diagonal element; to provide for expanding a central zone of the covering along one or more sinuous paths extending span- Wise along and across the chord line of the leading edge; and to provide simplicity of construction, convenience of manufacture and effectiveness of operation.
These and other objects and advantages of .the invention Will be apparent from the following description.
In the accompanying drawings which form a part of this specification and in which like numerals are employed to designate like parts throughout the same,
Fig. 1 is a perspective View of protective apparatus having a plurality of sinuous inflatable tubes installed on the leading edge of an airfoil, parts being broken away and in section,
Fig. 2 is a plan view from above of a modified construction of the protective covering shown in Fig. 1, before mounting on the airfoil, parts being broken away,
Fig. 3 is a view like Fig. 2 showing another modication of the protective covering, and
Fig. 4 is a perspective plan View from above of a further modification of the protective covering, parts being broken away and in section.
In an embodiment of the invention illustrated in Fig. 1 a protective apparatus I!) includes a body or covering I I of resilient rubber or other rubberlike material mounted at the leading edge of an airfoil I2 such, for example, as a wing of an aircraft. The covering I is constructed and arranged to provide a substantially smooth aerodynamic contour around the leading edge for maintaining the aerodynamic characteristics of the airfoil. The body II may be adhered throughout the extent of its inner surface I3 to the skin of the airfoil I2 or may be attached in a suitable manner as by screw fasteners (not shown) at its upper and lower attaching margins I4 and I5, respectively. For the latter arrangement of attachment, the covering is mounted in a condition of stretch between the margins I4, I5 to hold the covering against the airfoil when not in operation.
The rubber body or covering II has embedded therein a pair of adjacent inflatable tubes or elements It and I'I curved uniformly about the chord line I3 of the leading edge and 180 out of phase relative to each other, the tubes having walls of suitable resilient rubber-like material. The tubes are arranged in an overlapping manner and each extends spanwise in a sinuously curved path along the leading edge and across the chord line I8, the tubes i t, Il being in overlying relation at spacedapart regions where they diagonally cross the chord line.
It is desirable that the inflatable tubes I6, I'I be disposed adjacent the outer surface of the covering iI and have walls of considerable stretchability. Such walls may include in the rubber thereof reinforcing material such as stockinette or other knitted or otherwise stretchable fabric, preferably of nylon or rayon, although cotton or other suitable material may be used. The stookinette fabric is stretchable both circumferentially and longitudinally of the tube, which permits extensive stretching of the tube Wall for expanding the cover locally at the tube zone to break and loosen the ice thereon for removal by the ambient airstream. However, the reinforcing material in the walls of the tubes I6, I'I may, if
desired, be of substantially inextensible material such, for example, as square-woven, straight-laid fabric for imparting stretching force to adjacent rearward portions of the covering I0 upon inflation thereof.
The inflatable tubes I6, I1 have curved portions or reaches 2|, 22 and 23, 24 extending diagonally back and forth across the chord line of the leading edge, and have their adjacent margins at separated positions as at 25, 26, and 21, 28 and p i loosen such particles for their removal by the ,airstream.
The fabric and rubber part-s of the covering are united by vulcanization and heat under pressure. In the operation of the protective covering III,
when such covering is provided with inflatable tubes IS, li having highly stretchable walls, the two tubes may be inated in a cyclical manner individually or simultaneously and may be inated through suitable connector and conduit means in communication with such tubes at one end thereof and with a suitable source of air under pressure which may be located within the body of the aircraft, for example. These tubes then distend outwardly to a substantially semicircular shape in cross-section as shown by broken lines at 3l and 32 in Fig. 1, the Walls 4of such tubes stretching locally to a relatively greatextent within themselves by virtue of the stretchable action of the nylon fabric. Opposite loop portions 341, 3-5, 3 and 3l of these sinuous tubes at the regions `of reverse curvature tend, upon ination, to spread apart due to the curvature of the leading edge, which spreading acti-on coacts with the cracking action of the tubes at the diagonally extending curved portions 2l, 22, 23 and 26 to provide the desired lateral movement of the broken ice formation along the latter portions for its removal by the. ambient airstream. When the tube l5, for example, is inated, the central tube zone 20 is expanded along the sinuous path of such tube back and forth across the chord line of the leading edge and the outer portion of the rubber body ll overlyingr such tube I 5 is stretched extensively with little or no stretching force Vupon theV adjacent portions rearwardly of this tube le.; A similar stretching and expanding action occurs uponv `inflation of the sinuous tube Il; The local stretching of these tubes I6,
Y Il is found to be highly effective, especially at the immediateleading edge region, in cracking and loosening the ice formation, which cracking occurs in reaches; diagonally of the chord line of the leading edge rather than parallel thereto. Parts ofthe broken iceare moved laterally relative to and about the chord line for action thereonby the ambient airstream. In this manner Vsuch ice formationupon the covering is removed promptly and thoroughlyLespecially throughout the extent of the central tube zone 2o.
4'/Vhen the protective covering IU is `provided with inflatable tubes it, il having walls of substantially inextensibl'e fabric, the covering is mounted in `a condition` of stretch l'mtweenv attaching margins Id', I 't5 a'svdescribed hereinabove, and the tubes IB', lima-y be inated in av cyclical manner individually or simultaneously. `By virtue of the relatively inextensible walls-of the tubesY l', l'l, these tube-s, when inflated, distend outwardly and assume an expanded condition havingA lesser sharpness ofcurvature than that of the semi-circular shape obtained when the tubes have Walls of highly stret-chable fabric. Upon inflation of such tubes; they expand the covering at the central A'tube zone 2e, cracking the` ice for,-
niation thereon in reaches diagonally of .the chord lineof the leading edge and alongl the sinuous paths back and forth across such cho-rd line, and moving portions of the ice laterally relative to the chord line forremoval bythe iiow of, air. VThis action ,isV also effective in imparting stretching forceY to and moving outwardly from the airfoil the adjacentrearward portions ofthe covering ,lo to break and loosen the ice formations 'on the, latter portions. In this manner the covering is, expanded along overlapping sinuous paths spanwise throughout the central zone 2Q, and the rearward portions adjacent theY tubes are stretched a substantial. extent whereby :the 'ice formati-ons thereon` are cracked and broken for the thorough and prompt removal of such ice by the now of air across the covering.
The modied construction `of the protective covering di! of suitable resilient rubber-like material is constructed and arranged in a manner similar to that of the protective covering It except that a single tube 4| is disposed in a sinuous path extendingrspanwise back and forth across the chord line i8 -of the leading edge, which tube l may be inflated by a suitable conduit and connector means 12in communication therewith at an end of the protective covering. The rubber walls of the tube!!! may include reinforcing material of substantially inextensible fabric for stretching rearward portions of the covering 4Q or'may include highly stretchable fabric like nylon stockinette fabric therein for local stretching of the covering along the sinuous path of the tube. For the arrangement shown in Fig. 2, the tube El' is not continuously curved relative to theY chord line I8 but comprises substantially straight portionsV or Lreaches 43,114, 45 extending diagonally across the chord line and at an angle of inclination with respect to such chord line I8, adjacent straight portions 43, 44 beingopposingly inclined relativel to each other. TheV chordwise extent of the covering included within the central tubezone is such as to make possible the desired twisting and lateral shifting movement diagonalli7 acrossv the chord line I8' of partsof the ice formation upon the-breakingand cracking thereof due to the inflation of tube 4I thereby facilitating the action` of the ambient air-stream in further loosening and removing the'broken pieces of' ice. The operation ofthe covering 40, when installed on the'leadn'g edge ofthe airf'oil, is substantially as described hereinabove-for the covering l0.
l'f desired, two of Fig. 2 may be arranged together in 130"phase relationship orrin other desired relationships'.
For the modiedconstruction ofthe protective covering 5B of suitable resilient rubber-like'mate- Y rial shown in Fig. 3, one or more tubes 5l', 52 exa sinuous path may be provided yandmay be in- Vlated by suitable conduit and .connector means 53 `in communication therewith. These't'ubes 5l, 52 are embedded' in the rubberv body of the. protective covering in the manner, described hereinabove for the protective Vcovering it and the rub-'- ber walls thereof may include reinforcing material of suitable substantially inextensible fabric or of suitable highly stretchable fabric. The tube 5I has straight portionsV or reaches 54', 54 extendingV diagonally across the chordk line VI3 and at an angle of inclination relative to such chord line, and includes straight portions 55, 55 extending chordwise substantially normal to the chord line I8, adjacent inclined portions and adjacent normal portions being generally parallel.
rIhe provision of two gtubes as in the embodiment of Fig. 3 makes possible various phase relan tionships, as desired. For example, the two tubes maybe arranged in phase, 90`V or 180 out of phase, or in other desired arrangements, and one tube may be in the same'fo'rmation vas the other or more tubes of theformation sinuous path of the tube, and along the inclined straight portions 54, 54 the cracked ice isshifted laterally by virtue of inflation of such tube 5I as described hereinabove for the covering I0.
In the embodiment of Fig. 4, a protective covering 60 of suitable resilient rubber-like material includes inflatable tubes 6I, 62 disposed in the central tube zone 63 between attaching margins 64 and 65 and includes stretchable portions 66 and 6l extending rearwardly from the central zone 63, such stretchable portions having spacedapart apertures 10, 'l0 extending therethrough for venting the covering 60. The attaching margins 64 and 65 include therein reinforcing strips 68, 66 of suitable relatively inextensible fabric material folded about metal Ibead elements 69, 69.
The covering 60 is mounted on the airfoil in a condition of stretch between the attaching margins 64 and 65 as by suitable screw fasteners (not shown) extending through the rubber material and the reinforcing strips 68, 68 inwardly of the bead elements 69, 69. An offset arrangement is provided for mounting a fairing strip (not shown) for facilitating smooth flow of air across the covering at such margins.
Theinatable tube 62 having a wall of suitable resilient rubber-like material includes in such Wall expansion-limiting reinforcement of suitable substantially inextensible fabric material and such tube is embedded in the rubber covering 60 desirably adjacent the inner surface thereof. The tube 62 is disposed centrally about the chord line I8 and extends in a straight path along such chord line. When the tube 62 is iniiated and distended outwardly, it assumes a generally rounded form in section which action moves the stretchable portions 66 and 61 outwardly from the airfoil and imparts stretching force to the portions 66, 61, effectively breaking and loosening the ice thereon for thorough and prompt removal by the flow of air over the covermg.
The tube 6I has a Wall of suitable resilient rubber-like material and includes therein highly stretchable nylon stockinette fabric. The tube 6l may be superimposed upon the tube 62 adjacent the outer surface of the covering 60. Such tube 6| extends along the central tube zone 63 in a sinuously curved path back and forth diagonally across the chord line I8 of the leading edge. As described hereinabove for the covering I6, when the tube 6| is inflated, the protective covering 6D is expanded locally at the central zone 63 along the sinuous path of such tube 6I breaking and loosening the ice formation along the latter tube and providing the desired lateral shifting movement of the broken pieces of ice into the path of the ambient airstream whereby such pieces are thoroughly and promptly removed.
lln the operation of the covering 60 the inflatable tube 6I is inflated first for locally expanding such covering at the central zone and facilitating the effective removal of the ice formation immediately at the leading edge along the chord line I8. The tube 6I is then deflated and the tube 62 is next inflated, which action further promotes removal of any remaining pieces of ice at the central zone 63 and stretching the stretchable portions 66, 61 for cracking and breaking the ice formation thereon for removal by the ambient airstream. If desired, the two superimposed tubes 6I, 62 maybe inflated simultaneously.
. ratus comprising a covering for said leading edge comprising resilient rubber-like material having an inflatable tube extending along the covering and throughout the width of its bore diagonally across a subst-antially straight line along the covering with a portion of said tube throughout the width of its bore disposed entirely to one side of and spaced from said line and with another portion of said tube throughout the width of its bore disposed entirely to the other side of and spaced from said line, said covering being constructed and arranged to present upon ination of said tube a distended surface of the covering substantially coextensive with the Width of said tube throughout its extent.
2. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering for said leading edge comprising resilient rubber-like material having an inflatable tube extending in a sinuous path along the covering crossing and recrossing a substantially straight line along the covering at spaced-apart positions along said line with portions of the tube throughout the width of its bore disposed entirely to one side of and spaced from said line and with other portions of the tube throughout the width of its bore disposed entirely to the other side oi and spaced from said line, said covering being constructed and arranged to present upon inflation of said tube a distended surf-ace of the covering substantially coextensive with the width of said tube throughout its extent.
3. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering for said leading edge comprising resilient rubber-like material having an inflatable Itube including stretchable fabric material in the wall thereof for local stretching of said covering and extending in a sinuous path spanwise along the covering crossing and recrossing =a substantially straight spanwise-extending line of the covering at lspaced-apart positions along said line with portions of the tube throughout the width of its bore disposed entirely to one side of and spaced from said line and with other portions of the -tube throughout the width of its bore disposed entirely to the other side of and spaced from said line, said covering being constructed and arranged to present upon ination of said tube a distended surf-ace of the covering substantially coextensive with the width of said 'tube throughout its extent.
4. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said appa- Iratus comprising a covering for said leading edge comprising resilient rubber-like material having a plurality of inflatable tubes in superimposed relation to one another extending along the covering, at least one of said tubes extending in a sinuous path along the covering crossing and recrossing a substantially straight line along the covering at spaced-apart positions along said line in overlapping relation with another of said tubes to the other side of and spaced vfrom said 1ine,-
said covering being constructed and varranged to present upon inaition of said` sinuous tube Va distended surface of the covering lsubstantially coextensive with the width of such tube thro-ughouti'ts extent. y
5. Apparatus for preventing the accumulation of ice ori-the leading edge vof an airfoil, said apparatus comprising a covering Vfor said leading edge comprising resilient rubber-like'material having a pair 'iniiatable `tuloesin superimposed relation to one another each extending in a sinuous path along the covering crossing and reerossing a substantially straight'line along the covering atspaced-,apart positions along said linein overlapping relation With-,the other v tube at saidpositions, vthe portions of said pairof inflatable tubes between the crossing positions being disposed on opposite sides of and spaced from said line, and said covering being `constructed and arranged to present upon inflation ofv each inatable tube a distended surface of the covering substantially coextensive :with -thewidth of the l'tube throughoutits extent. Y Y
ii. Apparatus for preventing the accumulation o f ice on the leading edge, said apparatus com-` @rising aycovering for sai'dleading edge compris` ingV resilient rubber-like material lhaving va pair of inatabl-e tubes -in superimposed relation to one another "each extending 4in a 4substani'fially continuously curved sinuous path spanWise along the coveringy crossing and recrossing a substantially straight spanwise -extending 'lneatgspacedapart position's'along -said 'line vin overlapping relation with the other tube at said positions, the portions of said pair Ao .f inatable tubes vbe-` tween the crossing Apositions being disposed on opposite sides of and spaced -from said line, and each Yofthe inflatable tubes including stretchable fabric material in the Wall thereof lfor local distentionof the covering upon -ination of the tubes to present a curved surface yof the covering lsubstantially coextensive with the Width of the tube throughout its extent. c
' ROBERT CAMPBELL.
Number Name j "Date 2,025,919 wane V V nec. 31', 1935 2,251,430 Taylor Allg. 5, 1941 2,327,034 Geer I7, 1943 c