Heath

The two Heath patents in suit were issued to appellant to cover the use of cellophane and pliofilm as protective sheets for stencils. Before cellophane was used as a protective sheet, mere outlines were all that could be made on duplicating stencils with the stylus by anyone other than an expert without weakening the structure of the stencil. Without cellophane, the stylus picked up the minute fibers and destroyed the stencil structure, so that when the stencil was placed on the duplicating machine, the longitudinal pull on the stencil broke down the stencil fibers further and pulled the stencil apart.

The differentiation between the cellophane patent and the pliofilm patent is that the cellophane is particularly adapted to use where drawings are made with styli on the stencil, while pliofilm improves the cutting of stencils by type impression. The closed letters of the alphabet do not chop through in typing as they did in early stencil cutting or with cellophane.

At the time of filing the appellant’s complaint, in the lower court, the appellees • were engaged in selling stencils with plio-film and cellophane cover sheets. The plio-film cover sheet was adhered to the stencil by…