1. Field of the Invention
This invention relates to a method for making sheet material and more particularly, to a flotation method for forming a plurality of very thin, flat, pre-formed design pattern elements into a tightly-packed single layer, and the application thereof to a substrate prior to consolidation of the material into a finished product such as a floor or wall covering.
2. Description of the Prior Art
In the production of vinyl type floor and wall coverings in which the decorative wear surface includes, or is comprised of, a plurality of small pre-formed pattern elements positioned on a backing in close proximity to one another with the area between adjacent elements filled with a plastic material, the common practice has been to place a thin layer of design elements on a traveling substrate and, by imparting a vibratory motion thereto, orient the pattern elements with respect to one another in an arrangement wherein they form a single layer with the elements touching each other at at least one point on their peripheries. The application of vibratory motion to the substrate and pattern elements thereon is required to move the elements into a uniform arrangement one element thick because it is very difficult, using prior pattern element feeding means to avoid having pattern elements overlap or being disposed upon one another or having relatively large gaps between adjacent pattern elements. U.S. Pat. No. 3,056,224 exemplifies this type of operation. U.S. Pat. No. 3,150,022 discloses another arrangement for forming a single layer of flat pre-formed design elements prior to their application to a backing. In this arrangement, a randomly spaced arrangement of the elements are fed onto a first moving belt which carries them under a plate extending across the width of the belt. The plate is spaced away from the belt a distance only slightly greater than the thickness of one of the pattern elements to allow only a single thickness layer of the elements to pass thereunder. The pattern elements are then moved onto a second belt moving at a speed below that of the first belt. This causes the elements to bunch up into a tightly packed single thickness layer which is then secured to a backing. Other related variations of this type of operation are disclosed in U.S. Pat. Nos. 3,323,935; 3,012,901; and 3,540,411.
Prior methods of orienting chips on the surface of a substrate have not been entirely satisfactory in that when the vibratory method of orienting the chips was used, there was a lack of positive control of the spacing between the chips and/or control of the overlapping of the chips. Passing of the chips on a moving carrier under a plate spaced away from the carrier a distance only slightly greater than the thickness of the pattern elements has proven to be unsuccessful when thin chips such as those of the present invention are used in that the chips tend to clog up under the scraper and tend to ride up over each other when the rate of movement of the carrier is slowed and there is no certainty of control over spacing of the chips with relation to each other.
As disclosed by U.S. Pat. No. 3,679,784, it is known to form decorative articles suited for incorporation into polymeric flooring materials such as vinyls by placing and spreading quantities of different-colored plastisol on a body of liquid immiscible with the plastisol and having a density in excess of that of the plastisol. The separate bodies of plastisol may be brought together so that the juxtaposed inner edges thereof meet at irregular but clearly defined interfaces. The plastisol may be gelled and fused while it is on the support liquid and may be removed therefrom by bringing the substrate into surface contact with the liquid plastisol and then lifting the substrate.
U.S. Pat. No. 3,551,244 discloses a film laminate producing method wherein a polymer solution is dispersed on a water surface to form a film. The film is then removed continuously from the water surface by a support member which passes upward from below the water through the film-water interface so that the film adheres to the support member. The film may be broken into flakes before removal. The depth and rate of flow of the water may be used to control film formation.
The problem not solved by the prior art is how to form a plurality of small, very thin, pre-formed flat chips of differing colors, shapes and dimensions into a tightly packed layer of randomly arranged design elements and apply this layer to a substrate to obtain a surface having a thickness equal to that of a single chip and having substantially no overlaps or excessive spaces between the chips. This problem is solved by the present invention.