Method, device and apparatus for dispensing polyurethane mixtures

An apparatus for foaming a panel, comprising:

• supporting means for supporting a substrate to be foamed;
• a dispensing station for depositing, continuously over time, for processes lasting more than 30 minutes without any interruption, along a transverse section with respect to an intended advancement direction of a substrate, a series of thin, uniform films of reagent resins that are highly reactive and have a gel time of less than 36 seconds, said thin, said dispensing station be configured for arranging uniform films side by side so as to cover with expansion of a foam an entire width of substrate;
• wherein said dispensing station includes at least one dispensing for dispensing a liquid polyurethane mixture, the at least one dispensing device being fed by a respective mixing head;
• the at least one dispensing device including an inlet section suitable for receiving a liquid mixture generated by a combination of chemically reactive component resins with an addition of an expanding agent and solid powder charges, nano charges, or emulsifying gases;
• an outlet slit section arranged transversely to said advancement direction and configured to dispense a thin, uniform film of said liquid mixture having a width corresponding to an extension of said outlet slit section;
• an upper valve element and a lower valve element, mutually coupled and having a first conveying and containing surface and a second conveying and containing surface, respectively, facing each other and being spaced apart so as to define a gap chamber for distribution and advancement of the liquid mixture from said inlet section to said outlet slit section, said gap chamber being shaped in a diverging manner from said inlet section until it reaches a same width as said outlet slit section;
• wherein said first conveying and containing surface and second conveying and containing surface have geometric shapes complementary to each other, and are spatially shaped so as to define, for various fractions of said mixture, respective paths radiating from the respective inlet section to respective equidistant zones of said outlet slit section, wherein said paths all having a same extension length, so that all fractions of the liquid mixture will travel equal distances from the inlet section to the outlet slit section, in equal times, maintaining equal average speeds along each section having zones placed all at a same path distance either from the inlet section or from the outlet slit section, so as to inhibit formation of dishomogeneous layers of reacted resins, with a consequent dishomogeneity of the exiting film;
• said apparatus including:
• a dual conveyor having a plurality of mutually articulated plate or slab members, arranged to support and advance, along said advancement direction, a panel progressively obtained through foaming of said substrate, and arranged to counteract a thrust of expanding foam;
• wherein said plate or slab members include:
• wheel dragging means lying on a vertical plane, protruding to engage with central screw driving means, to be drawn along said advancement direction;
• and
• rail elements extending along said advancement direction, and arranged so as to laterally guide said wheel dragging means, while supporting a thrust of the foam in a central area of the structure of a dual conveyor;
• and
• thrust bearing wheel units arranged close to a central zone and to side zones of each plate or slab member, and configured to act as supports and to counteract thrust from expanding foam as well as to limit a deflection of several sections of each respective plate or slab member to a minimum.