Plastic fan blade for industrial cooling towers and method of making same

Abstract

A molded, composite, airfoil-defining, synthetic resin blade for large diameter cooling tower fans is disclosed wherein a moderately dense synthetic resin foam core is first formed that is generally of the same size and shape as the final desired blade. A shank embedded in the foam core extends outwardly from the end of the blade that is adapted to be fastened to the fan hub. A skin of fiberglass reinforced synthetic resin material is placed over the foam core with the thickness of the skin being greatest at the hub end of the blade and especially around the shank. The foam core with the skin thereon is molded into the final desired configuration thereof under pressure and temperature conditions such that the core is compressed and the thickness reduced to an extent correlated with the thickness of the synthetic resin skin on opposite faces thereof. Compression of the core enhances conversion of the fiberglass reinforced synthetic resin layers into a laminar monolithic skin by virtue of curing of the synthetic resin skin between the compressed core and the mold. The core is provided with stepped areas on opposite sides of the core which increase in height in a direction away from the shank. A sufficient number of pre-prepared, flexible sheets of fiberglass reinforced resin material are placed over the stepped areas to substantially fill the space between the mold and said stepped areas of the core during curing of the resin.