LIQUID/LIQUID, LIQUID/GAS OR GAS/GAS SEPARATION Method General operations by centrifugal force, using centrifuges or free-vortex apparatus using magnetic or electrostatic effect Apparatus General operations by centrifugal force, using centrifuges or free-vortex apparatus , using magnetic or electrostatic effect SOLID/LIQUID OR SOLID/GAS SEPARATION Method General operations by centrifugal force using centrifuges or free-vortex apparatus using magnetic or electrostatic effect Apparatus General operations by centrifugal force using centrifuges or free-vortex apparatus , using magnetic or electrostatic effect SOLID/SOLID SEPARATION Method Dry methods material in bulk Individual sorting Screening, sifting, pneumatic sorting using pneumatic tables or jigs by magnetic or electrostatic effect by centrifugal force using centrifuges or free-vortex apparatus Wet methods General operations flotation, differential sedimentation screening Combinations Dry methods - wet methods Apparatus Dry methods material in bulk Individual sorting Screening, sifting, pneumatic sorting using pneumatic tables or jigs by magnetic or electrostatic effect by centrifugal force using centrifuges or free-vortex apparatus , Wet methods General operations flotation, differential sedimentation screening Combinations Dry methods - wet methods This subclass covers: layered products comprising different kinds of material or layered products not characterised by the particular kind of material used; a product similar to a layered product but comprising only material in the form of a sheet or network embedded in a mass of plastics or of physically-similar substances which mass penetrates the said sheet or network and lies on both sides of the latter (e.g. so that the sheet or network reinforces the plastics substance) provided that the embedded sheet or network extends coherently or connectedly over substantially the whole area of the product; thus the embedded sheet or network may be a fabric or a series of rods connected by cross wires. The manner of making such a product is, however, classified in this subclass only if it is essentially a process of building-up an assembly of layers of which at least one outer layer is preformed. If the embedded material comprises only a series of unconnected rods, the product is not classified in this subclass. This subclass does not cover: processes or apparatus used in, or in connection with, the production or treatment of any product, if the process or apparatus is solely applicable to and fully classifiable in a single other class or subclass for processes or apparatus, e.g. , , , , , ; compositions or preparation or treatment thereof, unless they are essentially restricted to layered products and cannot be fully classified in another class without ignoring this restriction; etched metallic pattern on the surface of a printed circuit board. In this subclass, a film formed on a layer by spreading a substance thereon is not considered to constitute a layer itself if it serves only as an adhesive or its purpose is merely to finish a surface of a product. In this subclass, the following terms or expressions are used with the meanings indicated: "layer" is a sheet or strip or anything else having a small thickness relatively to its other dimensions which, together with at least one other layer, exists in a product, whether it pre-existed, e.g. as a separate sheet or strip, or was formed during the production of the layered product. It may or may not be homogeneous or cohesive; it may be an assembly of fibres or pieces of material. It may be discontinuous, e.g. in the form of a grating, honeycomb, or frame. It may or may not be in complete contact with the next layer, e.g. a corrugated layer against a flat layer; "layered product" comprises at least two layers secured together. The term "secured" includes any method of uniting layers, e.g. needling, stitching, gluing, nailing, dovetailing or the interposition of an adhesive or adhesive impregnated support. It may also be an intermediate stage in the production of an article which is not layered in its final form, e.g. a panel with a protective layer which is stripped off when the panel is placed in its position of use. The layers are preformed layers or layers formed in situ on a preformed layer and may consist of coherent solid materials, including honeycombs and other cellular materials or of non-coherent solid materials composed of assemblies of strands, strips, fibres, tiles or the like; "filamentary layer" means a layer of threads or filaments of any substance (e.g. wires) of more or less unlimited length placed in an orderly arrangement and secured together; it may be woven, knitted, braided, or netted, or formed of threads crossed or laid side and bonded together; "fibrous layer" means a random assembly of fibres or filaments, usually of limited length, e.g. felt, fleece; the fibres may or may not be interengaged or connected, e.g. by adhesive. In groups , at each level of indentation, in the absence of an indication to the contrary, classification is made in the first appropriate place. Layered products are classified in groups or if not characterised by their structure or composition. The classification of layered products is provided for in many classes, most of which are confined to a particular kind of material. However, in order that this subclass may provide a basis for making a complete search with respect to layered products, all relevant subject matter is classified in this subclass even though it may also be classified in other classes. LAYERED PRODUCTS CHARACTERISED BY Their structure general shape , layer structure , relation between layers Substances used bituminous or tarry substances, water-setting substances , metal, glass, ceramics, mineral fibres or particles , , wood, paper, cellulosic plastic substances , , rubber, synthetic resin , other substances Their properties MAKING LAYERED PRODUCTS Methods or apparatus for laminating Ancillary operations Controlling or monitoring Other operations, e.g. repairing