Patent Publication Number: US-6665949-B1

Title: Drying tool for honeycomb core

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     (Not Applicable) 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     (Not Applicable) 
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to drying tools for drying moisture present within cells of honeycomb cores, and in particular to a drying tool with an inflatable bladder compartment from which a plurality of open-ended nozzles protrude and through which upstream hot air supplied to the bladder compartment is pinpointedly directed against the honeycomb core at a plurality of sites for forcing a circulation of hot air among the cells to thereby remove moisture content. 
     Honeycomb cores are commonly employed in the construction of many structures that require relatively light weight coupled with relatively strong integrity. Chief among examples of such structural requirements is that of components of an aircraft. In particular, floor panels, engine nacelles, flaps, leading edge components, overhead bins, galley cabinetry, and the like all can be fabricated using a honeycomb core sandwiched between adhesively attached external skin material such that an integrated strong construction is achieved while overall aircraft weight objectives are maintained. One such honeycomb core product that is widely utilized is fabricated from NOMEX aramid paper (NOMEX is a registered trademark of the DuPont Company, Wilmington, Del.), and exhibits flame and chemical resistence as well as good thermal insulation. 
     While initial fabrication of such honeycomb core products is relatively straightforward, the repair of a damaged product whose skin, typically a composite material, requires replacement, can be a difficult task. Specifically, two major factors contribute toward skin replacement success. First, because the replaced composite skin is applied before being cured and therefore is cured in place, a curing temperature at least above 200° F. must be applied to cure the composite material, and this temperature also heats the adjoining honeycomb core. Second, because of ambient exposure of the honeycomb core water moisture enters the honeycomb cells, and this trapped moisture can expand up to 1,200 times normal when the core is heated above the boiling point of water. When this expansion occurs, the cellular structure of the honeycomb core is damaged and disbanding of the replacement skin occurs. 
     As is thus apparent, proper repair of such a structure with a honeycomb core is greatly enhanced in relation to successful drying of the core structure. At present, such moisture removal is typically attempted by using heat blankets and/or blown hot air on top of the core to theoretically cause wicking of moisture upwardly within the core and thereby promote core drying. Unfortunately, however, this existing approach is generally inefficient since pockets of air inherently present in the core cells themselves resist circulation of applied heat and thus resist moisture wicking and drying. Consequently, a need is present for a drying tool capable of eliminating moisture present in honeycomb core cells and thus promote proper repair results for exterior skin patching. In accord therewith, a primary object of the present invention is to provide a drying tool capable of delivering hot air to moisture sites within a honeycomb core. 
     Another object of the present invention is to provide a drying tool constructed to simultaneously direct a multitude of hot-air streams precisely in line with core cells for forcing heat circulation and moisture desiccation. 
     Still another object of the present invention is to provide a drying tool whose directed hot-air streams are flexibly positional against a honeycomb core for intimate-interface contact with the shaped surface of the core. 
     These and other objects of the present invention will become apparent throughout the description thereof which now follows. 
     BRIEF SUMMARY OF THE INVENTION. 
     The present invention is a drying tool for drying moisture present in cells of a honeycomb core. The tool includes an inflatable bladder compartment having a bendable generally flat exterior surface and a plurality of open-ended nozzles protruding from this exterior surface, with each nozzle having a passage there through in fluid communication with the bladder compartment. Finally, a connector element is provided to be in fluid communication with the bladder compartment and connectible with a hot air source for delivering hot air into the bladder compartment for subsequent dispatch therefrom through the plurality of nozzles. Preferably, the nozzles are situated in a grid formation and are of a generally conical configuration. In use, the bendable exterior surface with the protruding nozzles is bowed or curved to generally configure to the exterior shape of the honeycomb core such that hot air is pinpointed in a grid pattern to drive heated air into the core and thereby cause circulation through the core cells for moisture evaporation. In this manner, a non-curedcomposite repair patch can be applied and adhered over and to the exposed honeycomb core portion and thereafter cured in place at a required cure temperature without fear of core damage due to moisture expansion and resulting disbanding of the patch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An illustrative and presently preferred embodiment of the invention is shown in the accompanying drawings in which: 
     FIG. 1 is a side elevation view of a drying tool for drying moisture present in cells of a honeycomb core; 
     FIG. 2 is a bottom plan view of the drying tool of FIG. 1; and 
     FIG. 3 is a side elevation view of a portion of the drying tool of FIG. 1 in association with a portion of a honeycomb core. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIGS. 1 and 2, a drying tool  10  is shown for use in drying moisture present in cells of a honeycomb core  12  (FIG.  3 ). The tool  10  preferably is fabricated of a flexible material such as silicone rubber to create a bladder compartment  14  having a bendable generally flat exterior surface  16  from which a plurality of open-ended nozzles  18  protrude and are situated in a grid formation such that each nozzle  18  is between about 0.10 and 0.50 inch, most preferably about 0.25 inch, from all immediately next-adjacent nozzles  18 . Each nozzle  18  preferably is a generally conical configuration and protrudes from the generally flat exterior surface  16  preferably between about 0.25 inch and about 0.75 inch, most preferably about 0.50 inch. A preferably generally-cylindrical passage  20  of a preferable diameter between about 0.01 inch and about 0.10 inch, most preferably 0.05 inch, is provided to each nozzle  18  to be in fluid communication with the bladder compartment  14 . Finally, a connector element such as a threaded opening  22  is in communication with the bladder compartment  14 . and connectible with a hot air source such as a complementarily threaded delivery tube (not shown) for delivering hot air into the bladder compartment  14  for subsequent hot-air dispatch therefrom through the respective passages  20  of the nozzles  18 . 
     In operation, and as illustrated in FIG. 3, the bendable exterior surface  16  with the protruding nozzles  18  is bowed or curved to generally configure to the exterior shape of the honeycomb core  12  such that hot-air is pinpointedly discharged from each nozzle  18  in a grid pattern to drive heated air into the core  12  and thereby cause circulation through the core cells for moisture evaporation. The most preferred grid formation, where each nozzle  18  is about 0.25 inch from all immediately next-adjacent nozzles  18 , is chosen to allow for variations in core types while also focusing on currently popular cell sizes. As opposed to simply providing circulating hot air over the core surface and not within the core as performed in the prior art, by providing pinpoint, and thus penetrating, hot-air discharge from each nozzle  18  aimed at the cells at the wall of the honeycomb core  12  as here taught, an entry and exit flow of circulated heated air can occur within every other cell. In this manner, deep core drying is accomplished efficiently in a relatively short period of time such that patch application and patch curing can be performed without lengthy downtime or repetition due to patch disbanding. 
     While an illustrative and presently preferred embodiment of the invention has been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by prior art.