| 摘要 |
The invention relates to the sealing of the shaft journal (9) of a discharge pump, especially a gear pump for molten polymers. Sealing is effected by means of a barrier fluid which according to the invention is a solvent for the polymer and is passed, at a slight positive pressure, into an annular cavity (27) which surrounds the drive-side shaft journal (9) and in an axial direction is bounded on both sides by stuffing-box packings (17, 18) held at a distance by spring elements (20). Owing to this design of the discharge pump, the inevitable leakage of the polymer delivered at high backpressure and high temperature is limited, and solidification, which impairs the sealing effect of the stuffing-box packings (17, 18) and makes them ineffective, is prevented. The barrier fluid can be circulated in a circuit consisting of reservoir (24), down main (32) and rising main (31), and be cooled and monitored at the same time. Further proposals relate to avoiding stagnation of the melt in chambers with reduced melt flow and the pressure relief of the bearing casing (10, 10.1) by a relief duct (16) connected to the suction side (5) of the pump, and by an inverse gap control to reduce friction and wear on the lateral faces of the gear wheels. <IMAGE>
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