Recent environmental regulations and approaching exhaustion of old-growth timber supplies have made it increasingly difficult and expensive for manufacturers to obtain high-grade lumber to use in their wood products. Such products include furniture, cabinets and millwork. This is particularly a problem for products which are stained rather than painted because the stain does not cover any underlying irregularities in the wood. With painted products, on the other hand, many of the defects in the wood are covered by the finish.
One way of addressing the shortage and high cost of high quality lumber is use of veneered stock. Typically, veneered parts are created by laminating a high quality, i.e., clear, veneer over a lower grade core material, such as medium density fiberboard (MDF), particle board, plywood or finger-jointed stock. Use of veneered parts results in a substantially more efficient utilization of high quality wood, and therefore reduces raw material costs. Unfortunately, the actual process of applying the veneer can be relatively complex.
Veneering is relatively simple if only a single flat surface or two opposed flat surfaces, i.e., one or two sides of a piece of plywood, must be covered. However, covering adjacent sides of a core is substantially more difficult. In particular, multiple processing steps are required to cover adjacent sides. In a first step, the veneer is applied to one of the adjacent sides. The other side of the partially veneered piece must then be surfaced or milled to remove excess glue or overhang of the first applied piece of veneer. After the milling step, the second piece of veneer can be applied. Lastly, the edges of the second piece of veneer must be milled. Thus, applying veneers to two or more adjacent surfaces is a time-consuming and costly process.
Another difficulty incumbent in applying a veneer to two adjacent sides simultaneously is supplying sufficient heat to quickly cure the thermosetting adhesive that is often used for veneering. In particular, at least with thicker veneers, simple conduction heating from heated platens is relatively slow and creates a significant bottleneck in material processing. Radio frequency (RF) heating, on the other hand, heats at a rate that is substantially independent of the thickness of the veneer. Unfortunately, heating two perpendicularly oriented glue lines using RF techniques is difficult because of the preferential heating of glue lines oriented parallel to the electric field. The preferential heating is believed to lead to excess heating of the parallel glue line prior to achieving adequate heating of the perpendicular line.
It is therefore an object of the present invention to provide a system for applying a veneer on two or more adjacent sides of a core in a single step.
It is another object of the present invention to provide a system of veneering that eliminates the need to resurface the core between veneering steps.
One more object of the present invention is to provide a system for veneering that results in a visually attractive corner.
Another object is to provide a system of veneering that is flexible enough to accommodate an edge band with the veneer in a single step.
Yet another object of the present invention is to provide a system for pressing and heating a veneered article.
It is also an object of the present invention to provide a system for pressing and heating a veneered article that can heat orthogonal glue lines in a single step.