More particularly, the present invention is directed to a relatively inexpensive lay-up mold which is light weight and of uncomplicated design.
BACKGROUND OF THE INVENTIONBACKGROUND OF THE INVENTION Precisely contoured, high performance outer surfaces are required for many components of aircraft, satellite and similar applications. These components are commonly made from composite materials, i. e. sheets of carbon or graphite fiber impregnated with resin and subsequently cured.
The sheets of composite material are provided with the desired precise contour by laying a composite sheet on a precision contoured surface, e. g. high density polyurethane foam which has been machined to match the desired surface using state-of- the-art procedures.
The precision contoured surface forms part of a"lay-up"mold which, up to this time, have been expensive, cumbersome assemblies.
SUMMARY OF THE INVENTIONSUMMARY OF THE INVENTION The present invention is a lay-up mold comprising: a multi-sided vertically extending frame formed of steel sheet; a plurality of spaced apart, vertically extending, ribs formed of steel sheet positioned within said frame and rigidly affixed thereto, said ribs having upper edges which conform to a pre-determined mold surface; a plurality of spaced apart vertically extending partition elements formed of steel sheet positioned within the frame transverse to said ribs and rigidly affixed to the frame and the ribs and being vertically co-extensive therewith to define open-topped compartments within the frame; said partition elements having upper edges which conform to said pre-determined mold surface; a base member formed of one or more layers of perforated steel sheet rigidly affixed to the frame and the upper edges of the ribs and partition elements; and a coating of polyurethane overlying and bonded to and interlocked with the perforated steel sheet, the coating conforming to the pre-determined mold surface.
BRIEF DESCRIPTION OF THE DRAWINGSBRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view, partly in section, of a lay-up mold in accordance with the present invention; Figures 2,2A, 2B illustrate the frame of the lay-up mold of the present invention; Figures 3,3A-C illustrate a base member for a lay-up mold of the present invention; Figure 4 is a somewhat more detailed view of the lay-up mold of Figure 1; and Figure 5 shows a molded article resulting from the mold of Figure 4.
DESCRIPTION OF THE INVENTIONDESCRIPTION OF THE INVENTION With reference to Figure 1, a lay-up mold in accordance with the present invention is indicated at 10 comprising a vertically extending frame 20 which is multi- sided with sides 22,24,26,28,30 and 32 formed of steel sheet, e. g. plain carbon steel, as also shown in Figure 2, with the cut-outs 40 being provided to decrease the weight of frame 20. A plurality of spaced apart vertically extending ribs 50 also formed of steel sheet are positioned within the frame 20, extending between the sides 26,24; 28,22; 30,32 and rigidly affixed to frame 20. e. g. by welding as indicated at 52. A plurality of spaced apart, vertically extending partition elements 53, also formed of steel sheet, are positioned within the frame 20 and rigidly affixed therein, e. g. by welding as indicated at 54. Partition elements 53 extend transverse to adjoining ribs 50 and form open topped compartments 60. The upper edges 54 of partition elements 53, and the upper edges 51 of ribs 50, with reference to 51', 54', Figures 2A, 2B conform to a predetermined mold surface indicated at 65 in Figure 1.
With reference to Figures 3,3A, 3B, and 3C, perforated steel sheet, indicated at 70, in one or more layers, is fitted to the upper edges of ribs 50, and partition elements 53, e. g. by hand pressure, and affixed thereto, e. g. by welding as indicated at 74 in Figure 3A. Polyurethane is sprayed from nozzle 80 as shown in Figure 3C, onto perforated steel sheet 70, shown also in Figure 3A, and a coating of polyurethane foam 180 is formed on perforated steel sheet 70 and adheres thereto and interlocks with perforated steel sheet 70 by filling apertures 75 and forming anchors of polyurethane foam underneath the perforated steel sheet 70 as shown at 77 in Figure 3C. The perforated steel sheet 70, with a conforma coating 180 of polyurethane foam supported on frame 20, ribs 50 and spacer elements 53 represents a lay-up mold in accordance with the present invention as shown in Figure 1. The conformal polyurethane coating 180 can be optimized to the degree required by conventional programmed machine tool treatment. With the polyurethane layer 180 satisfactorily contoured, a flexible sheet of resin impregnated carbon or graphite cloth 90, with the resin partially cured is laid on polyurethane layer 180 and conformed to the contour of the layer 180, suitably using conventional autoclave pressurization or vacuum techniques, while heating the sheet to fully cure the resin. The resulting molded article 100 is shown in Figure 5, after removal from a mold 10. The precision contoured surface of the article is indicated at 105. The underlying surface 110 is only nominally conformal.
The lay-up mold of the present invention is easily constructed of inexpensive, relatively light material, i. e. steel sheet to which is anchored an easily contoured polyurethane layer; the mold is easily assembled and transported.