| 摘要 |
<p>In injection moulding the thermoplastic material which has become viscous through heating is supplied to an injection moulding nozzle and from there is passed into the fitted injection mould. Contaminants, e.g. metal frag-ments, are held back at the dirt filter barrier gap. When a large amount of dirt has collected upstream of the barrier gap, the dirt prevents the further through-flow and must be removed. Hitherto, for this purpose the filter housing is opened, the barrier member removed and the filter chamber cleaned. The filter chamber now is hollowed out from an openable housing in which a loose barrier member is positively engaged in the filtering position, with a feed line hollowed out from the housing and which issues with a circular crosssection coaxially to a flow axis in the filter chamber. A drain line of circular cross-section is hollowed out from the housing and emanates from the filter chamber side opposite to the opening of the feed line and coaxial to the flow axis. The filter chamber and the outline of the barrier member are constructed in rotationally symmetrical manner to the flow axis and smooth, the internal diameter of the filter chamber, measured at right angles to the flow axis, is larger throughout than the external diameter, measured on the same axial height, of the barrier member located in the filtering position. The difference between these two diameters in the flow direction initially decreases to a barrier cross-section of an annular barrier gap and then increases again downstream thereof. With the housing closed, the barrier member is displaceable from its filtering position into a cleaning position along the flow axis and with the barrier member in the cleaning position an annular cleaning gap is formed in place of the barrier gap, the passage width of the cleaning gap being larger than that of the barrier gap.</p> |
