Abstract:
A deicer ( 10 ) for a radome ( 12 ) includes an active portion ( 16 ) through which transmission occurs and a non-active portion ( 18 ) which is attached to an aircraft ( 14 ). The deicer ( 10 ) comprises a cap portion ( 20 ) covering the active portion ( 16 ) of the radome ( 12 ) but unattached thereto. The cap portion ( 20 ) comprises layers ( 36, 38 ) defining inflatable/deflatable chambers ( 24 ), the layers both being made of non-extensible material such as square woven nylon fabric. When the chambers ( 24 ) are inflated, the inner layer ( 38 ) lifts off of the active portion ( 16 ) of the radome ( 12 ). The deicer ( 10 ) can additionally comprise a skirt portion ( 22 ) which is stretchable to accommodate the inflation of the chambers ( 24 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates generally as indicated to a radome deicer and, more particularly, to a radome deicer having inflatable/deflatable chambers for use on an aircraft antenna radome. 
     BACKGROUND OF THE INVENTION 
     A radome is provided as a protective housing for antennas or other equipment which transmit and/or receive electromagnetic waves in hostile environments. In some applications, such as with a radome installed on an airplane or helicopter, the radome is highly susceptible to icing. Ice build-up on the outside surface of a radome can contribute to attenuation and distortion of the transmitted/received electromagnetic waves and thus must be removed if the equipment is to operate appropriately. 
     In the past, deicers have been used to remove ice accumulation on aircraft structures such as, for example, airfoils, impeller blades, and/or intake nozzles. Such aircraft deicers are generally designed to effectively remove accumulated ice without overly impacting any important flight forces (e.g. lift, drag, weight). A radome deicer must not only meet this criteria, but must also be designed to avoid adversely altering the incoming/outgoing electromagnetic waves so that transmission effectiveness is not reduced. Moreover, a radome deicer often presents other special design considerations not usually encountered with other aircraft deicers. 
     SUMMARY OF THE INVENTION 
     The present invention provides a radome deicer which removes ice accumulation without sacrificing transmission effectiveness. 
     More particularly, the present invention provides a radome deicer comprising a cap portion covering the active portion of a radome but unattached thereto. The cap portion can comprise an inner layer and an outer layer defining inflatable/deflatable chambers. When the chambers are deflated, the inner layer lies flat against the active portion of the radome. When the chambers are inflated, the inner layer is lifted off the active portion of the radome. The inner and outer chamber-defining layers can each be made of an non-stretchable material (e.g., square woven nylon fabric) so that the inflated chambers have a tube shape with a roughly circular cross-section. A stretchable skirt portion can be attached to the cap portion to allow the deicing cap to lift off of the active portion of the radome when the chambers are inflated. 
     This construction of the radome deicer allows it to be thinner than conventional pneumatic deicers. Specifically, the thickness of the cap portion is less than 0.070 inch, less than 0.060 inch, and/or about 0.050 inch. This is at least 0.020 inch thinner than a conventional deicer wherein the inner chamber-defining layer is bonded to the aircraft structure and the outer chamber-defining layer is made of an extensible material. A deicer according to the present invention having a thickness of about 0.050 inch is especially suitable for use on a radome wherein the housed radio equipment receives/transmits at higher frequencies. 
     The deicer of the present invention can be constructed so that an active radome portion having a complex compound-curved shape can still be covered with a square woven fabric. Specifically, the carcass of the radome deicer has a cap portion made from two non-extensible layers (which define the chambers) and a skirt portion made from an extensible layer. The non-stretchable chamber-defining layers can be formed from a plurality of panels. For example, if a dome-shaped distal portion of the radome is its active portion, roughly triangular panels can be joined together to form the cap portion of the carcass. 
     The carcass can be provided with a fluid-path construction that allows the use of an external air connection located remote from the radome base as is sometimes necessary if the radome is internally pressurized. Specifically, a channel is formed in the carcass by an extension tab of the non-extensible layers which is secured to the extensible layer by seams. The channel communicates with the chambers and can extend through the skirt portion whereby fluid can be introduced and evacuated to inflate and deflate the chambers. 
     The carcass can be constructed to prolong the fatigue life of the deicer by preventing over-stretching and cracking of a cover layer of the deicer. Specifically, the seams on the outer surface of the carcass can each comprise a stitch line, a gum coating over the stitch line, and a fabric strip over the gum coating. These seams may include chamber-defining seams, cap-skirt attachment seams, channel-forming seams, and/or chamber-closing seams. 
     Thus a radome deicer according to the present invention can be constructed thinner than conventional pneumatic deicers, can accommodate geometric shapes with square woven fabric, can be compatible with remote air connections, and/or can maintain an acceptable fatigue life. 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 can be employed. 
    
    
     DRAWINGS 
     FIG. 1 is a schematic illustration of a deicer according to the present invention installed on a radome of an aircraft. 
     FIG. 2 is a perspective view of the radome deicer in a deflated condition. 
     FIG. 3 is a perspective view of the radome deicer in an inflated condition. 
     FIG. 4 is a cross-section of the radome deicer in the deflated condition. 
     FIG. 5 is a cross-section of the radome deicer in the inflated condition. 
     FIG. 6 is an enlarged cross-section of the deicer. 
     FIG. 7 is another enlarged cross-section of the deicer. 
     FIGS. 8 and 9, are front and rear views, respectively, of a carcass of the deicer. 
     FIG. 10 is an enlarged cross-section of a seam of the carcass. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings in detail, and initially to FIG. 1, a deicer  10  according to the present invention is shown installed on a radome  12  of an aircraft  14 . The radome  12  provides physical protection for aircraft antennas (not shown) which transmit and/or receive electromagnetic waves. 
     Referring now to FIGS. 2 and 3, in the illustrated embodiment, the radome  12  includes an active distal portion  16  through which transmission occurs and a non-active proximate portion  18  for attachment to the aircraft  14 . In the illustrated embodiment, the radome&#39;s distal portion  16  has a dome shape that roughly resembles a half-egg shape (the more pointed half). The proximate portion  18  has a roughly cylindrical shape extending tangentially therefrom. 
     The radome deicer  10  is shown in a deflated condition in FIG.  2  and in an inflated condition in FIG.  3 . The deicer  10  includes a cap portion  20  which covers the radome&#39;s distal portion  16  and a skirt portion  22  which covers the radome&#39;s proximate portion  18 . The skirt portion  22  is attached to the radome  12  along its lower circular circumference by, for example, cementing it thereto. The other portions of the deicer  10 , and particularly the cap portion  20 , are unattached to the radome  12 . 
     Referring additionally to FIGS. 4 and 5, it can be seen that the deicer&#39;s cap portion  20  includes chambers  24  which transform the deicer  10  between its deflated condition (FIGS. 2 and 4) and its inflated condition (FIGS.  3  and  5 ). In the illustrated embodiment, the chambers  24  are positioned in parallel planes perpendicular to the axis of the radome  12 . The chambers  24  have about the same width and, with the illustrated dome-shaped cap portion  20 , have descending diameters towards the cap&#39;s distal end. 
     The chambers  24  are each connected to a pressure/suction source (not shown) so that they can be selectively inflated/deflated during flight. When the chambers  24  are deflated, the deicer&#39;s cap portion  20  lies flush against the outer surface of the radome  12  in a flattened condition. (FIG. 4.) When the chambers  24  are inflated, the deicer&#39;s cap portion  20  is lifted off of the outer surface of the radome  12  by the curved inner contour of the inflated chambers. (FIG. 5.) As the chambers  24  are inflated, the deicer&#39;s skirt portion  22  stretches or expands to accommodate the lifting of the cap portion  20 . (Compare FIGS. 4 and 5.) 
     Referring now to FIGS. 6 and 7, it can be seen that the illustrated deicer  10  comprises a fabric carcass  30 , an outer cover layer  32 , and an inner base layer  34 . The carcass  30  comprises a cap portion  36  formed by non-stretchable fabric layers  38  and  40  (FIG. 6) and a skirt portion  42  formed by a stretchable fabric layer  44  (FIG.  7 ). The outer cover layer  32  is bonded to the outer surfaces of the fabric layers  38  and  42  and the inner base layer  34  is bonded to the inner surfaces of the fabric layers  40  and  42 . 
     The cap fabric layers  38  and  40  are each made of a square woven nylon fabric with rubber skim coating for sealing and are each approximately 0.012 inch thick. The outer cover layer  32  is made of a non-conductive neoprene and is approximately 0.010 inch thick. The inner base layer  34  is also made of non-conductive neoprene and is approximately 0.010 inch thick. Alternatively, the inner base layer  34  can be made of natural rubber gum and be approximately 0.012 inch thick. Thus, the cap portion  20  of the deicer  10  can have a thickness of less than 0.070 inch, less than 0.060 inch, and/or less than or about 0.050 inch thereby providing superior performance, especially with high frequency waves. The deicer  10  can be made so that its cap portion  20  is at least about 0.020 inch thinner than a conventional carcass having at least one of its cap fabric layers made of a stretchable fabric (i.e., knit nylon). 
     The skirt fabric layer  44  is made of a knit nylon fabric and is approximately 0.022 inch thick. However, it may be noted that thickness is not a crucial design criteria in the skirt portion  22 / 42  since it does not cover a transmitting portion of the radome  12 . Instead, the important design parameters for the deicer skirt portion  22  and/or the carcass skirt portion  42  are sufficient stretch when the chambers  24  are inflated for ice-removal purposes and adequate attachment to the radome  12  for installation purposes. For this reason, the thickness of the layer  44 , the layer  32 , and/or the layer  34  can be increased in the skirt portion  22  of the deicer  10  if necessary or desired. 
     Referring now additionally to FIGS. 8 and 9, the carcass  30  is shown isolated from the other layers of the deicer  10 . In the cap portion  36  of the carcass  30 , the outer non-stretchable fabric layer  38  is formed from six triangular panels  50  sewn together by axially extending seams  52 . Although not visible in the drawings, the inner fabric layer  40  is formed from similar panels joined with similar seams. This construction allows the deicer cap portion  20  and/or the carcass cap portion  36  to cover the complex compound-curved surface of the distal portion  16  of the radome  12 . 
     The chambers  24  are defined by radial seams  54  and the bottom edge of the carcass cap portion  36  is joined to the carcass skirt portion  42  by a radial seam  56 . As seen in FIG. 9, a channel  60  extends upwardly (in the illustrated orientation) through the carcass skirt portion  42  to the carcass cap portion  36  and interrupts the chamber-defining seams  54 . The channel  60  forms a conduit from the pressure/suction source to the chambers  24 . This fluid-path construction allows the use of an external air connection located remote from the radome base (i.e., two inches away) as is sometimes necessary if the radome is internally pressurized. 
     In the illustrated embodiment, one end of each chamber  24  is left open to the channel  60  and the other end is closed by a short axial seam  62 . The open end and closed end can be alternated between adjacent chambers. For example, in the illustrated orientation, the lowermost chamber is unseamed on its left end and seamed on its right end while the next-up chamber is seamed on its right end and unseamed on its left end. Also in the illustrated embodiment, the channel  60  is formed by an extension tab  64  of the carcass cap portion  36  which is attached to the carcass skirt portion  42  by seams  66 . 
     Referring now to FIG. 10, a panel-joining seam  52  is shown in detail which is used to join the panels  50  of the outer fabric layer  38  of the carcass cap portion  36 . The illustrated seam  52  includes a stitch line  70 , a gum coating  72 , and a fabric strip  74 . On the outer surface of the layer  38 , the gum coating  72  is applied to the stitch line  70  and the fabric strip  74  is secured thereto. A suitable material for the stitch line  70  is nylon thread and a suitable material for the gum coating  72  is natural rubber. The fabric strips  74  can be made of the same material as the layers  38  and  40 , that is square woven nylon fabric with a rubber skim sealing coat. All of the panel-joining seams  52 , the chamber-defining seams  54 , the cap-skirt attachment seam  56 , the chamber-end seams  62 , and the channel attachment seams  66  can be constructed in a similar manner so that all stitch lines on the outside surface of the carcass  30  have the gum coating  72  and the fabric strip  74  applied thereto. This seam construction is believed to prolong the fatigue life of the deicer  10  by protecting the outer cover layer  32  from over stretching and developing cracks above the seam lines. 
     One may now appreciate that the present invention provides a radome deicer  10  which effectively prevents ice accumulation without sacrificing antenna transmission characteristics. The deicer  10  can be constructed to be thinner than conventional pneumatic deicers, to cover complex curved geometric shapes with square woven fabric, to be compatible with remote air connections, and/or to have an acceptable fatigue life. 
     Although the invention has been shown and described with respect to a certain preferred embodiment, 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.