Flush door made of single ply veneer door skins

Jan. 4, 1966 a. elmendorf 3,226,902

FLUSH DOOR MADE OF SINGLE PLY VENEER DOOR SKINS Filed

Oct. 24, 1963

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INVENTOR.

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United States Patent

3,226,902

Patented Jan. 4, 1966 .

3,226,902

FLUSH DOOR MADE OF SINGLE PLY VENEER DOOR SKINS

Armin Elmendorf, 860 Charleston Road, _r

Palo Alto, Calif. °

Filed Oct. 24, 1963, Ser. No. 318,621

Claims. (Cl. 52—615)

This invention relates to wood panels with specially processed skins. In particular, it relates to a flush door io made of single-ply veneer door skins, i The problem which this invention has solved is the utilization of a single-ply of low grade veneer for door skins in place of the conventional 3-ply plywood panel of the same thickness, usually Vs -inch. 15

It is economically desirable to make wood panels or doors with a single-ply of veneer as for example in hollow doors. Attempts to make such doors have been made by facing the veneer with paper but the surface of the door with such a structure reveals cusps or dishing at breaks or splits in the veneer when the veneer shrinks, as in low humidity weather. These are especially evident when the door is painted. Such cusps reduce the commercial acceptance of the door. Nor does the paper facing on the veneer conceal open defects such: as knot holes or splits in the veneer or Open joints. I have discovered how all such open defects can be completely concealed thereby making possible the economies that lie in the use of a single-ply of veneer in place of the conventional 3-ply door skin. .

The problems in making such wood panels or doors are even greater when low grade veneer is used in order to obtain low costs. Low grade veneer may contain defects such as knot holes, splits and worm holes that render it unfit for use in doors and other hollow panels ³⁵made of a wood frame enclosing a grid of narrow, widely spaced wood or paper strips on edge.

Hollow doors generally have a core composed of a wood frame and a grid and are usually faced with thin plywood % to %6-inch thick on each side. ⁴⁰

Cusps in single-ply door skins applied to grid cores appear to be caused by differences in the direction of the major shrinkage stresses in adjacent pieces of veneer. This happens when two pieces of veneer that are butted _ together edge to edge are faced with paper that spans the ⁴⁵joint. The paper prevents shrinkage of the veneer on the face side causing it to warp and to show dishing on either side of a break. Such cusps develop at joints or splits in the veneer in areas where it is not bonded to a solid base as in the grid area enclosed by the door frame, where ⁵⁰it is only bonded to the edges of widely separated narrow strips of wood, or veneer, or paper. While the elements of a grid are generally parallel, this is not always the case. The grid or support of the skins may also consist of fiber rings or sinuous strips of paper on edge. Splits or tears in the veneer reveal their presence by slight dishing of the surface on either side of the break, when paper-faced veneer is bonded to a solid frame and to a grid containing wide open spaces. Such shallow valleys may become conspicuous when the door is painted. The value of the resultant door is thereby reduced.

Large knot holes in single-ply door skins must be plugged to prevent the paper face from being punctured in use, but small knot holes generally less than about 72-inch in diameter, would be acceptable were it not for the expansion of the paper at the knot hole in high humidity causing the paper to deflect or bulge at the hole, thereby making the door commercially unacceptable.

A primary object of my invention is to provide a wood panel or door which eliminates the foregoing disadvantages.

One object is to make a wood panel or hollow door of single-ply door skins faced with paper in which the paper covered veneer will not develop cusps.

Another object is to make a wood panel or hollow door out of single-ply door skins in which inexpensive low grade veneer containing defects may be used.

Another object is to make a wood panel or a hollow door having a skin of low grade veneer in which splits or tears are not revealed.

The foregoing objects are attained as well as other objects which will become apparent in the ensuing specification and drawings. The invention will be shown in the following description and the attached drawings wherein:

FIGURE 1 is a plan view of a hollow door;

FIGURE 2 shows a perspective of a section on an enlarged scale of a door and

FIGURE 3 shows a perspective of a similar door on an enlarged scale with , an alternative honeycomb grid 20 core.

I have discovered that often open defects in the veneer can be completely concealed, thereby making possible the economies that lie in the use of a single ply of veneer containing such defects. I have found that the cusping 25 adjacent to defects such as splits or open joints in the veneer are eliminated if the veneer is divided into narrow elements on either side of the break. This may be done in a number of ways, as for example, by flexing the veneer in the manner described in my U.S. Patent No. 2,974,697, 30 or by subdividing it by means of parallel slits as described in my U.S. Patent No. 2,468,595. Recourse may be had to these patents for a detailed explanation of the various methods for subdividing the veneer.

Subdividing the veneer into narrow elements, however, sometimes introduces a disadvantage. The slits or fine breaks introduced may show through a paint finish especially if the paper is thin. They “telegraph” through the paper. I have found that, such defects can be obliterated by means of a thin nonshrinking mineral coating applied over the paper. Other defects can also be concealed, such as gaps at veneer joints, splits and knots. In order that the tendency to cusp at the slits or fractures introduced by slitting or fracturing the veneer be eliminated, these must be close together. The distances between such slits or fractures should not be more than about three times the thickness of the veneer.

The simplest procedure is to apply such a nonshrinking facing layer over the entire surface of the panel. The facing layer should preferably be of a composition that also lends itself to subsequent sanding. Various binders or synthetic resins or oils may also be used as the binding agent, or hardening may be due to setting of the surface coat as when gypsum is used. The composition of mineral facing surfaces involving minerals and a binder is not 55 a part of this invention, and will not be described in detail. It is only necessary to say that the mineral coating must be tough so that it will not crack when the unbounded door skin is handled, and it must be easily applied. The well-known filler compositions used for filling pits in surfacing particle boards may be used.

A typical non-shrinking composition which lends itself to application by means of blades or rollers, is one made by adding polyvinyl acetate to freshly mixed gypsum stucco and applying the same in a thickness of at least 2 65 mils. A door skin with this composition may be handled without cracking. Such a surface on each side of the door, contributes to the dimensional stability of the door and reduces any tendency to warp that may reside in the underlying structure. Flatness is one of the most im70 portant properties desired in a door. A thickness of 5 mils using 10% polyvinyl acetate based upon the dry weight of the gysum gives good results. Such a mineral

3,226,902 ³ surface is hard and tough, and therefore increases the resistance of the door to scratching.

Referring to the drawings, a door panel is shown in which the panel has a core made of a door frame and a grid of widely spaced parallel wood elements on edge such as 3. The grid is preferably enclosed by the door frame. The door skins shown generally as 4 have a veneer 5 further shown as having two defects, namely a split 6 and a hole 7, in the veneer of the door skin. A paper facing 8 is shown bonded to the veneer as well as a mineral facing 9.

FIGURE 3 shows a door with a different grid. The door skin is shown generally as 10 and it includes a veneer 11 showing as defects a split 12 and a hole 13. A paper facing 14 and a mineral facing 15 are suitably bonded to the veneer. The core has a doorframe 16 and a grid 17 which consists of a honeycomb such as 18. The honeycomb may consist of large sinuous folds of paper on edge.

Whereas I have shown and described an operative form of the invention, it should be understood that this showing and description of the invention is to be taken in an illustrative or diagrammatic sense only. There are many modifications to the invention which will fall within the scope and spirit thereof and which will be apparent to those skilled in the art. The scope of the invention should be limited only by the scope of the hereinafter appended claims.