The present invention is directed to an apparatus and process for making molded columns and, more particularly, to a two piece mold for making columns.
In recent years, molded columns have been used in place of wooden columns in residential construction. Molded columns have a number of advantages, such as lower costs, a variety of shapes, structural strength, etc. Various types of molding processes have been used to make columns.
One molding process currently used is to provide an elongated mold having a hollow cavity. Viscous material is poured into a mold cavity and the mold is spun at high speed to force the molding material against the inner surface of the mold. This process is known as centrifugal casting and works well for columns with a circular cross-section, but is not well-suited for square or rectangular columns. In the case of a square column for example, the material accumulates in the corners of the column. Thus a square column will have overly thick corners that use an excessive amount of material and will have thin walls between the corners that may have inadequate strength characteristics.
Another molding process includes forming a cavity between outer and inner molds in which at least the inner mold is constructed of a flexible material. The viscous material is poured within the cavity and given time to gel. The inner mold must be removed because the material shrinks during the gelling and curing stages. To accomplish this, a vacuum is applied to an interior of the inner mold causing it to contract inward away from the gelled member. The contracted inner mold may then be removed allowing the material to continue curing and gelling. However, the inner mold folds inward upon itself when the vacuum is applied becoming wedged within the gelled member. This may result in the member becoming damaged while the inner mold is being extracted, or may cause excessive wear on the inner mold resulting in a shorten usable life.
The present invention is directed to a mold and a molding process for forming elongated columns. A cavity is created between an outer mold and a flexible inner mold in which a molding material is poured that creates the column. During the curing process, an extraction member is placed within the flexible inner mold and a vacuum is applied remove air from within the inner mold. The vacuum causes the inner mold to contract inward away from the molding material and adhere to the extraction member. At this point, both the extraction member and the inner mold may be removed and the molding material remains in the outer mold and cures to a hardened state.
The extraction member has a surface area that is larger than that of the inner mold. This larger size causes the inner mold to adhere to the extraction member without folding or collapsing upon itself when the vacuum is applied and become stuck within the molding material.
The extraction member may have a variety of shapes and configurations. In one embodiment, the extraction member is cruciform shape with a plurality of arms extending outward from a center section. The arms extend into corners of the inner mold to provide support and give shape during the initial molding process when the molding material is still in a viscous state. The extraction member may further include apertures such that air is removed from all sections of the hollow interior of the inner mold when the vacuum is applied. Other extraction member configurations include diamond shaped, and rectangular shape. The sides of the extraction member may further be substantially straight, or may be curved. The outer and inner molds may have a variety of shapes, including substantially rectangular and substantially circular.