Abstract:
Methods and apparatus for filling form gaps are disclosed. In one embodiment, a method includes providing a heating and pressurizing dispenser for thermoplastic, heating and pressurizing a thermoplastic in the dispenser, discharging the thermoplastic through a nozzle attached to the dispenser and filling the gap in a form with the discharging thermoplastic from the nozzle. In other aspects of the invention, the thermoplastic includes polypropylene with talc. In another aspect of the invention, a composite product is produced by providing a form, and filling the gaps in the form with thermoplastic, and forming the composite product against the form. In yet another aspect to the invention, a high temperature and high pressure dispenser for filling gaps in forms is provided.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to forming processes, and more specifically, to methods for assembling forms.  
       BACKGROUND OF THE INVENTION  
       [0002]     Form mats with grids of sharp pins are often used for forming acoustical surfaces in many applications, including aircraft engine covers such as cowls or nacelles. Pin areas or pinbeds are assembled from sections or sheets with grids of sharp pins, known as pinmats. The pins on these pinmats perforate the material being fabricated during lay-up and forming, forming an acoustically dampening surface. Surfaces formed with pinbeds often include fiber resin composites typically used for aircraft components. Pinbeds may be assembled by placing segments of pinmats on an underlying form or tool. The pinmats are cut to shape and adhered to the tool or form to produce a pinbed area on the form. Using several pinmats or trimmed pinmat sections, large and/or contoured areas on a form may be covered with pinmats. The material to be formed is then laid up on the form with the covering pinmats, or the form and the pinmats are pressed against the material being formed. After the form is removed from the product, the product is left with a perforated surface.  
         [0003]     In other applications, contoured surfaces, ribbed surfaces, or smooth surfaces may be produced during lay-up and/or curing of formed products by utilizing textured mats attached to an underlying form or tool. As with pinmats, the textured mat is placed against the product being formed, leaving the desired surface after cure and removal of the form.  
         [0004]     During assembly of pinbeds with pinmat segments, it is sometimes difficult to obtain tight contact between adjoining pinmats attached to the underlying form or tool. For example, a prior art pinbed  3  including four adjoining pinmats  5  with pins  7  is shown in  FIG. 1 . Between the pinmats  5  are gaps  10 . The gaps  10  may also include corner mismatches, such as the corner mismatch  11 , where adjoining corners of pinmats  5  meet. In this example prior art pinbed  3 , there are approximately 100 pins square inch. The pins  7  are molded integrally with a backing mat. The pins  7  are approximately one-eighth inch high, and the mat is approximately one-eighth inch thick. The gaps  10  between the adjoining pinmats  5  may form a space where the material being formed can migrate during lay-up and cure, to a detriment of the final surface on the finished product.  
         [0005]     More specifically, during forming and cure of heat activated fiber resin composites, such as utilized in aircraft, gaps  10  in the pinbed  3  can lead to resin lumps and lines in the final surface that need to be sanded down or otherwise corrected. Resin migration into the gap  10  can also occur, leaving a deficit of bonding resin or fiber movement in areas of the product adjoining the gaps. The gaps  10  can thus result in hand corrective work on the component being formed, and sometimes to the discard of the component. Resin may also penetrate gaps  10  and stick to the underlying forms (not shown), resulting in effort to clean the forms for subsequent use prior to subsequent forming operations. This may also cause undue wear or damage to the forms.  
         [0006]     Gap filler materials have been utilized to fill gaps  10  in pinbeds  3  to decrease the difficulties resulting from gaps in the forming pinmats. The gap filler material contacts the part being formed prior to and during cure. Thus the material is preferably compatible with the underlying component material. Epoxy-based materials have been used as gap fillers, but can bond to the underlying tool. The use of epoxy materials for gap filling also includes curing time, and the epoxy can shrink, leaving part of the gap unfilled. Sheet adhesives compatible with fiber resin composites have been utilized to fill gaps. The film adhesive is cut into strips and rolled into “noodles.” The “noodles” are stuffed into gaps  10  by hand using a putty knife. With the installation of the film adhesive noodles done by hand, considerable time can be consumed filling forming gaps between the pinmats, especially in complex cured surfaces.  
         [0007]     Therefore, a need exists for efficient application of a form gap filling material.  
       SUMMARY OF THE INVENTION  
       [0008]     Methods and an apparatus for filling form gaps are provided. In one embodiment, a method includes providing a heating and pressurizing dispenser for thermoplastic, heating and pressurizing a thermoplastic in the dispenser, discharging the thermoplastic through a nozzle attached to the dispenser and filling the gap in a form with the discharging thermoplastic from the nozzle. In other aspects of the invention, the thermoplastic includes polypropylene with talc. In another aspect of the invention, a composite product is produced by providing a form, and filling the gaps in the form with thermoplastic, and forming the composite product against the form. In yet another aspect to the invention, a high temperature and high pressure dispensers for filling gaps in forms is provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0010]      FIG. 1  is a plan view of a prior art pinbed with gaps.  
         [0011]      FIG. 2  is a side view of an exemplary application of a gap filler in accordance with an embodiment of the present invention.  
         [0012]      FIG. 3  is a flow chart of an exemplary method of filling form gaps in accordance with an embodiment of the present invention.  
         [0013]      FIG. 4  is a side view of an aircraft manufactured in accordance with an embodiment of the present invention  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     The present invention relates to methods and an apparatus for filling gaps in forms. Many specific details or certain embodiments of the invention are set forth in the following description and in  FIGS. 2 through 4  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several details described in the following description.  
         [0015]      FIG. 2  shows an exemplary application of molten thermoplastic  62  to fill a gap  10  in a form  6  in accordance with an embodiment of the present invention. The form  6  includes an underlying tool  1  covered with pinmats  5  (not to scale). The pinmats  5  include a multitude of pins  7  for perforating, by way of example, and not limitation, an aircraft component where an acoustical dampening surface is desired. With the pinmats  5  attached to the tool  1 , a gap  10  may occur between adjoining pinmats or between the pinmat and the underlying tool. In this exemplary embodiment, the gap  10  is filled with a thermoplastic material forming a gap filler fill  30  that, by way of example, not limitation, may include the same material as the pinmat  5 . For resin fiber aircraft parts, the thermoplastic may include a 20% talc filled polypropylene homopolymer, in this example PD2201, manufactured by M.A. Hanna, of Cleveland, Ohio. The polypropylene is a thermoplastic that softens or melts when heated. The gap filler fill  30  is installed between the adjoining pinmat sections  5  as softened or molten thermoplastic  62  from a high temperature and high pressure dispenser  40  similar to, but operating at a much higher pressure and temperature than, an industrial glue gun.  
         [0016]     The dispenser  40  includes a nozzle  43  for dispensing the molten thermoplastic  62 . After the molten thermoplastic  62  fills the gap  10 , the gap fill  30  can be smoothed if desired in any suitable fashion, including by hand utilizing a spatula or putty knife  50  prior to the molten thermoplastic  62  hardening.  
         [0017]     The dispenser  40 , by way of example, but not limitation, includes an electrically powered heater  80 , a pneumatically powered piston  70  that pressurizes a charge  60  of thermoplastic material being melted and having pressure applied, and a nozzle  43  for discharging the molten thermoplastic  62  to the gap  10  between the pimnats  5 . The heater  80  is powered through a power cord  83  to an electrical power source (not shown). The piston  70  is powered by a pressure hose  73  to an air pressure source (not shown). It will be appreciated that the piston  70  may suitably be powered by hydraulic or gear driven mechanisms.  
         [0018]     For polypropylene with 20% talc, temperatures exceeding 400° have been found to be suitable for melting this thermoplastic. A temperature of 450° F., plus or minus 10° has been found to suitably soften the polypropylene, while not burning it. The polypropylene material is comparatively thick, even in the melted form, and thus high pressure is suitably applied to force the molten thermoplastic  62  through the nozzle  43 . Pressures greater than 100 psi have been found to suitably pressurize the molten thermoplastic  62 . A pressure of 400 psi will suitably move the molten thermoplastic  62  through the nozzle  43 , and suitable pressures include pressures of 1000 psi or higher. The thermoplastic  62  is applied in a bead, like applying caulking. In an exemplary embodiment of the present invention, the nozzle  43  has a tip opening diameter of 0.05 inches, permitting a bead or stream of similar diameter of molten thermoplastic  62  to be placed into a gap  10  by holding the nozzle  43  proximate to or against the gap  10 .  
         [0019]     It will be appreciated that the dispenser  40  may be in any suitable configuration for application of molten thermoplastic  62  to gaps  10 . By way of example, but not limitation, the dispenser  40  here is configured in the shape of a hand-held gun permitting mobility of the dispenser  40  during application of the thermoplastic material  62  to gaps  10 .  
         [0020]      FIG. 3  shows a flow chart of an exemplary method  100  of gap filling of forms in accordance with an embodiment of the present invention. At a block  110 , pinmats are positioned adjoining each other on an underlying form. Separately, at a block  120 , a filler thermoplastic is heated and pressurized. At a block  130 , the form with the pinmats has its gaps filled with the application of beads of thermoplastic material in gaps between the pinmats.  
         [0021]     In areas where desired, at a block  140 , the filler may be smoothed. At a block  150 , the filling thermoplastic is allowed to cool. After cooling, the form is advantageously ready for immediate lay-up and forming of a product which is completed at a block  160 .  
         [0022]     Embodiments of apparatus and methods in accordance with the present invention may provide significant advantages over the prior art. For example, embodiments of the invention may advantageously reduce the labor and expense associated with filling the gaps between pinmats, and may also reduce the expense associated with reworking components manufactured according to the inventive processes. The number of rejected components may be reduced, and the overall quality of the products manufactured using embodiments of the invention may be improved.  
         [0023]     It will be appreciated that a wide variety of apparatus and methods may be conceived in accordance with alternate embodiments of the present invention to produce a variety of components. For example,  FIG. 4  is a side elevational view of an aircraft  600  having one or more composite components  602   a - d  formed in accordance with alternate embodiments of the present invention. In general, except for the components formed in accordance with the present invention, the various components and subsystems of the aircraft  600  may be of known construction and, for the sake of brevity, will not be described in detail herein.  
         [0024]     As shown in  FIG. 4 , the aircraft  600  includes one or more propulsion units  604  coupled to a fuselage  605 , wing assemblies  606  (or other lifting surfaces), a tail assembly  608 , a landing assembly  610 , a control system  612  (not visible), and a host of other systems and subsystems that enable proper operation of the aircraft  600 . It will be appreciated that apparatus and methods in accordance with the present invention may be utilized in the fabrication of any number of contoured or specially textured components  602  of the aircraft  600 , including, for example, the various components and sub-components  602   c  of the nacelles of the propulsion units  604  such as cowl sections  602   c , components and subcomponents of the tail assembly  608  such as rudder and stabilizer components  602   d , components and subcomponents of the fuselage  605  such as window and door brackets  602   a  and nose cones  602   b , and any other suitable portion of the aircraft  600 . And while the aircraft shown in  FIG. 4  is generally representative of a commercial passenger aircraft, including, for example, the 737, 747, 757, 767, 777, and 7E7 models commercially-available from The Boeing Company of Chicago, Ill., the inventive apparatus and methods disclosed herein may also be employed in the assembly of virtually any other types of aircraft. More specifically, the teachings of the present invention may be applied to the manufacture and assembly of other passenger aircraft, fighter aircraft, cargo aircraft, rotary aircraft, and any other types of manned or unmanned aircraft, including those described, for example, in The Illustrated Encyclopedia of Military Aircraft by Enzo Angelucci, published by Book Sales Publishers, September 2001, and in Jane&#39;s All the World&#39;s Aircraft published by Jane&#39;s Information Group of Coulsdon, Surrey, United Kingdom, which texts are incorporated herein by reference. It may also be appreciated that alternate embodiments of apparatus and methods in accordance with the present invention may be utilized in the manufacture of a wide variety of textured or formed components of, for example, boats, automobiles, canoes, surfboards, recreational vehicles, or any other suitable vehicle or assembly.  
         [0025]     While the preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.