US2414917A - Apparatus for molding wood or the like material - Google Patents

Description

Jan. 28, 1947. J YQUNG r 2,414,917

APPARATUS FOR MOLDING WOOD OR THE LIKE MATERIAL Filed March 29, 1944 2 Sheets-Sheet 1 INVENTOR JOH N YOU N G 'RNEY Jan. 28, 1947. YOUNG 2,414,917

APPARATUS FOR MOLDING WOOD OR THE LIKE MATERIAL Filed March 29, 1944 2 Shets-Sheet 2 INVENTOR JOHN YOUNG NEY Patented Jan. 28 1947 UNITED APPARATUS FQR MOLDING WOOD OR THE LIKE MATERIAL .iohn Young, Hagerstown, Md assignor to Duramold Aircraft Corporation, New York, N. Y., a.

corporation of Delaware Application March 29, 1944, Serial No. 528,603

3 Claims. 1

This invention pertains to the art of molding wood, or the like material, the invention comprising a novel structure of die, employed for molding Wood and similar materials.

In the art of molding wood, a layup is formed of the material to be molded, the layup being positioned in a die, which presents a rigid forming surface to the material. The forming surface comprises a contour companion to the de sired contour of the molded assembly. The molding operation consists of pressing the material against the forming surface, while heat is applied to set the layup to the contour of the forn ing surface.

As will be understood, by persons skilled in the art, the material of the assembly is usually fastened to the die by temporary fastening means, to hold the material in proper position opposite the forming surface until the molding pressure is applied. This is especially important when the layup comprises a number of pieces distributed over the area of the forming surface.

For example, the layup usually comprises a plurality of plies of. veneer. Each ply may consist of strips of veneer laid side by side in a predetermined pattern to cover the forming area. One practice is to make each strip long enough to extend beyond the forming area, and to fasten the strip at its end to the die by means of staples, tacks, or the like fastening means, driven. through the strip into the die at a point outside the bounds of the forming area. This practice is preferred, because the tacks, or staples, permit the material of the layup to yield under the molding pressure, to shift into conforming engagement with the surface contour of the die. The excess border material of the assembly, containing the staples, is subsequently removed.

Dies have been formed of a number of materials, for example, cement and wood having been used under prior art practice. In the patent to Potchen et al., No. 2,308,453, there is disclosed a die of preferred construction comprising sheet metal. Thedie being in sheet form, with uniform thickness, heat transmission through the die is uniform over the area of the forming surface. The die comprising metal, which is a good conductor of heat, operates to transmit heat to the layup. In the prior art use of massive wooden or cement dies, practically no heat is transmitted to the layup from thedie side, and heating of the layup is from the blanket side only.

In the prior art practice of wooden dies being used, the pieces of the layup are fastened to the die by tacks, or staples, driven into the die. Un-

der the more modern practice of using metal dies, as set forth in the patent to Potchen et al., No. 2,308,453, tacks will not hold in the material of the die.

The present invention is directed to a die structure, comprising a forming surface of a material into which tacks cannot be driven, but including a tacking member into which tacks, or staples, can be driven to hold the layup in position opposite the forming surface of the die. The invention is particularly applicable to thin sheet metal dies, such as are disclosed in the referred to patent, No. 2,308,453.

The tacking member is attached to the die located wherever it is desired to fastenv the pieces of the layup to hold them in position, preparatory to the molding operation. In the case of the prior art practice of tacking the layup along the border of the forming surface, the tacking member is attached to the die, bordering the forming surface area immediately outside the bounds thereof.

According to one practical embodiment of the invention, the tacking member constitutes a strip of suitable dimensions, which is fastened to the die to lie against the surface thereof. The strip comprises a material suitable for tacks to be driven into it, and in which the tacks will hold. Wooden strips, or plywood strips, for example, will serve the purpose.

The tacking member can be fastened to the die in any suitable manner. For example, an attachment fixed to the die, and a companion fastener associated with the tacking member, has been devised for the purpose. The attachment comprises one or more attachment members, ranged along the tacking strip, with a fastener member for each attachment member. The attachment members are located on the die surface in positions suitable for locating the tacking member in desired position relative to the forming surface,

The surface of the tacking member is preferably contoured continuous with the contour of the surface of the die, so that the die presents no sharp inside or outside corners against which the assembly is molded. For a similar purpose the surface of the fastener is contoured continuous with the surface of the tacking member.

One simple and practical means for fastening the tacking member to the die surface comprises one or more nuts, fixed to the die surface in positions within the area to be occupied-by the tacking member. The nuts can be fixed to the die surface in any suitable manner, for example, by being tack welded in position. Screws, companion to the nuts, serve as fastener members.

The preferred practice is to position the tacking member covering the nut, a cavity being provided in the member to contain the nut. Thereby the attachment is completely housed within the tacking member, and does not project to break the'contour of the forming surface. The screwsare projected through the tacking member to engage the nuts, the tacking member being countersunk to embed the screw heads. Flat head screws are preferably used, to present their exposed surfaces continuous with the strip surface.

A more complete understanding of the nature of the invention will be derived from the accompanyin drawings, to which attention is now directed. In the drawings- Figure 1 presents an exploded view in perspective, of airplane skin parts, any of which is capable of being molded in a die embodying the present invention,

Figure 2 presents a perspective View of a typical die embodying the invention, with parts broken away for clearness of illustration,

Figure 3 is an exploded fragmentary perspective view, illustrating the means for fastening tacking members to the die,

Figure 4 i a fragmentary perspective View, illustrating the tacking member fastened in position on the die,

Figure 5 is a fragmentary perspective view of a package ready for molding, illustrating practice of the invention, and

Figure 6 is a detail showing a, modified form of tacking member in cross-section.

Figure 1 shows the skin pieces of a typical aircraft construction, each piece capable of being molded on a die embodying the present invention. It will be understood that the invention is not limited to die for producing the particular skin structures illustrated in Figure 1. Nor is the invention limited to dies for producing airplane skin parts, the showing of Figure 1 being presented merely to illustrate typical application of the invention.

Figure 2 presents a typical die structure capable of producing one of the skin parts of Figure 1. The die of Figure 2 is particularly adapted for molding the skin piece I I of Figure 1. The invention is not limited to the die of Figure 2, the shown die being employed merely to illustrate a typical application of the invention,

The die, of Figure 2, comprises the body M which, in the embodiment shown constitutes a piece of sheet metal formed to the predetermined contour shown. The .die body I4 is contoured to provide the forming, or molding, surface I5. The particular contour of the die I4 shown forms no part of the present invention, the invention being applicable to dies for fabricating a vast diversity of parts.

The forming surface I5, of the die I4, presents a predetermined contour conforming with the contour desired for the piece I I, of Figure 1. The die I4 is of the female, or concave, type, and, therefore, the contour of the forming surface I5 conforms with the outside surface of the skin I I. The peripheral contour of the area I5, in Figure 2, conforms with contour of the border I2, of the piece I I, in Figure 1.

Dies for fabricating skin structures, such as the skin pieces of Figure 1, have been produced of a number of different materials. For example, molding dies have been made of cement, and of wood. Preparatory to the molding, operation, the

4 pieces of the material comprising the skin are commonly attached to the die by temporary attaching means, to hold the material of the assembly in position against the forming surface of the die until molding pressure is applied. One practice, according to the prior art, is to tack the material to the die surface, and for this reason wood dies have been preferred under prior art practice.

The present invention is particularly applicable to dies which comprise a material into which tacks cannot be driven, and Which will not hold tacks. More particularly th present invention applies to dies of thin sheet metal, such as are disclosed in the prior patent to Potchen et al., 2,308,453. Attached to the sheet metal die body I4, is the tacking member I8, the tacking member I8 being of a material into which tacks can be driven, and which will hold the tacks. Thus, under the preferred practice, the tacking member I8 is made of wood or plywood.

The usual practice of fabricating a structure, such as the skin piece II, of Figure 1, is to lay veneers of wood on the surface I5, a number of plies being laid in face to face relationship on top of each other to attain the desired thickness of skin. One practice is to supply the strips of veneer I 9, Figure 2, which are laid side by side to produce a ply which covers the area of theforming surface I5. Each strip I9 is laid with at least one end extending beyond the border of the forming surface I5, and the strip is attached to the die preparatory to the molding operation by one or more tacks, or staples 20, Figure 5, being driven through the veneer into the tacking member I8. One practice is to provide strips long enough to extend across the formin surface, from border to border thereof, and to tack the individual strips at their opposite ends. In this manner, each strip is fixed to occupy a predetermined position in the ply.

In the manner described several plies are laid up one on top of the other, until the desired thickness of skin is attained. The grain of the Wood in alternate plies is preferably disposed at relative to each other, the usual practice being to lay strips of successive plies in opposite directions at 45 from the layup.

The layup, formed in the manner described, is now enclosed in a molding cover 23, Figure 5, preferably in the form of a blanket of rubber. The blanket 23 is sealed at the edge of the die I4 by means of the C-clamps 24, to complete a package, which is now ready to moldthe assembly 28 to fabricate the skin I I. A suitable method for molding is fully disclosed in Patent No. 2,308,453, and requires no further description herein.

The tacking member I8 can be positioned anywhere on the surfaces of the die I2 where it is desired that the veneer strips should be attached to the die, to hold them in position against the forming surface I5. In the embodiment shown, the tacking members I8 constitute a tacking strip, which borders the area of the forming surface I5, immediately outside the bounds thereof.

Preferably, the material of the strip I8 is provided in standard cross-sections, so that it can be out to lengths dictated by the desired location of the tacking strip on the die surface. The edges of the strip I8 are preferably bevelled at 25, so that the contour of the surface of the strip in position on the die is continuous with the contour of the die surface. Thus, the layup 28, Figure 5, is molded smoothly, and without sharp inside or outside corners, which, if present, would crease the molding cover 23 under the molding pressure, and reduce the life thereof.

In Figure 6 is disclosed an alternative embodiment of the cross-sectional structure of the strip material used for tacking members. Figure 6 shows the strip 26 with the rounded surface 21.

In the embodiment shown in Figures 2 and 5, the tacking strip I8 is coextensive with the border of forming area I5, and is roughly parallel with the border of the skin II being molded. In the case of a portion of the skin periphery being reentrant, for example, to provide for the cockpit opening of the piece II, in Figure 1, the tacking member can follow a corresponding peripheral contour on the surface of the die I4, as illustrated at 30, in Figure 2. In this manner, a considerable quantity of layup material can be saved, and the layup time is reduced. In some cases, for

example, in the case of window openings 3|, of g Figure 1, the saving in material is insufficient to compensate for the added cost of layup labor. Accordingly, the openings 3| are cut in the molded skin by a subsequent trimming operation.

The molded assembly 28 is removed from the die, and is trimmed along the line A-B of Figure 5, the trim line A--B corresponding with the trimmed edge I2, of the skin piece I I, of Figure 1.

Any suitable means may be provided to fix the strip I8, positioned on the die I4, against the surface thereof. It is preferred however that, whatever attaching means be employed, the contour of the forming surface of the die is not broken; also that the die is not weakened. The preferred attaching means, as disclosed in Figures 3 and 4, comprise the attachment 34, fixed to the surface of the die I4, and the companion fastener 35, associated with the tacking member I8. The attachment 34, in the embodiment shown, comprises one or more nuts, fixed to the surface of the die by any suitable means, such as the tack welding 36. The fastener 35, comprises ascrew for each nut 34, companion thereto.

In the practice the nuts 34 are preferably ranged along the strip I8, in the area of the surface of the die to be occupied by the strip I8. It is preferred, as shown, that the nuts 34 be of a size to fit entirely within the mass of the strip I8, so that when the strip I8 is attached to the die I4, the nuts 34 are embedded within the stri I8. Cavities 31, are provided in the tacking member I8, to encompass the nuts 34, and to permit the strip I8 to lie against the surface of the die I4.

The screws 35 extend through the strip I8, as shown, each engaging a nut 34 to hold the strip I8 in desired position relative to the forming surface I5. The screw holes in the strip I8, are countersunk at 38, and flathead screws 35 are preferred, so that the screw heads present surfaces continuous with the surface of the strip I8.

It will be obvious to persons skilled in the art that the embodiment of the invention presented herewith is subject to a number of modifications, without departing from the scope of the invention. Accordingly, th invention is not to be limited by the specific disclosure contained herein, but is limited by the accompanying claims.

I claim:

1. A device for molding wood or the like material, comprising a metal die having a surface of predetermined area for forming the material, a tacking member bordering the area of the forming surface, a nut welded to the surface of the die within the area occupied by the tacking member, a screw fitting the nut and extending through the tacking member fastening it to the die, the nut being embedded in the tacking member whereby the tacking member is positioned-against said surface of the die, the contour of the surface of the head of the screw being continuous with the surface of the tackin member.

2..A device for molding wood or the like material, comprising a metal die having a surface of predetermined area for forming the material; a tacking member bordering the area of the forming surface; a nut welded to the surface of the die positioned for attaching the tacking member to said surface; a screw fitting the nut and associated with the tacking member for fastening the tacking member to the surface of the die.

3. In a device for the molding of wood or other moldable material by fluid pressure applied to the material through a flexible pressure tight blanket which urges the material against a forming surface of the die, the combination of a pressure tight metal die having a top surface including a molding portion adapted to support material to be molded and a marginal sealing portion surrounding said molding portion adapt: ed to receive the sealing portion of a blanket to form a pressure tight seal therewith; a tacking strip to which material to be molded on the molding portion may temporarily be attached by fastening elements driven into the strip, said tacking strip being secured to said metal die between said molding portion and said sealing portion.

JOHN YOUNG.

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