Drum-type screening machine

Abstract

A drum type screening machine has a centrifuging rotor within it. A perforated retaining element is carried by the shaft between a feed inlet and an entry region of the drum. The perforations of the retaining element are small enough to retain the foreign bodies which it is intended to retain but larger than the perforations of the screen. The retaining element has an access aperture, a closure element and means for holding the closure element movably in position to close the aperture. The retaining element can be a basket made up of a perforate plate with a perforate rearward flange. The closure element can be a half-moon segment, located by locating pins and rotatable on the shaft with respect to the remainder of the retaining element on clearing the locating means when pressed axially against the force of a bias spring. Use of the retaining element prolongs the screen life so much that tension adjustment become necessary. Provision is made for this to be done from outside of the machine. The screening drum has a pair of rings which support the screening cloth and which are held apart at an adjustable distance by tensioning bars. One ring is supported within an end member of the machine housing and the other on support means within the housing. Each bar is externally threaded, e.g. by way of an extension sleeve that is axially fast with the bar. The sleeve is engaged by an internally threaded nut which is axially fast with the end member of the machine. The sleeve extends through that nut and through the end member to the outside of the machine. A hexagonal head formed on the end of the sleeve can be turned exteriorly of the machine with a box spanner, thereby to tension the screen cloth.