Abstract: An apparatus and a method for injecting a liquid dye into a polymer melt, which includes a metering pump with a metering inlet and a metering outlet. The metering inlet connects to a dye tank and the metering outlet connects to a polymer melt carrying component. To add the liquid dye to the polymer melt in the melt carrying component in a quantity that is as uniform and accurate as possible, the invention provides for connecting the metering inlet of the metering pump to a feed outlet of a feed pump, which connects with its feed inlet to the tank. With that, it is possible to generate a feed pressure at the metering inlet of the metering pump, which can be adapted to an injection pressure at the metering outlet of the metering pump.

Abstract: A filtering device for a spinning head for producing plastic threads. The spinning head has a housing in which the plastic melt flows through a filter element under pressure before exiting the spinnerets. The filter element is provided with a filtering material that is subjected to an axial contact pressure through a distributor device, according to the degree of pressure of the melt. This contact pressure acts upon the sealing edges of the filter element to close the sealing gaps. The special geometrical configuration of the filter element and/or its elasticity guarantee advantageous filtering in terms of energy. The filtering system is resistant to pressure and provides good, permanent sealing.

Abstract: An apparatus for filtering plastic melts, which comprises a filter housing (1) having at least one cylindrical filter receiving chamber (8), and with a tubular filter cartridge (2) mounted in the chamber. An annular melt flow space (9) for the plastic melt is defined between the outer periphery of the filter and the inside wall of the chamber, such that the melt flows radially inwardly through the filter medium of the filter cartridge and into the central passage of the filter cartridge and then to an outlet opening of the housing. An additional melt flow outlet channel (12) is positioned adjacent the downstream end of the filter cartridge, and in one embodiment, the melt is able to flow via the additional melt flow outflow channel to the outside of the housing. In a second embodiment, the melt can flow via the additional melt flow outflow channel and an additional filter (11) and return to the main flow.