Greased journal bearing assemblies with thermal isolation and cooling in

Abstract

Continuous mixers of plastic materials are equipped with greased journal bearing assemblies instead of bulky, expensive, pumped circulating-oil lubricating systems, usually involving oil-cooling heat exchangers with circulating water. Such pumped oil systems having traditionally been employed in the past for lubricating journal bearings of the two rotors in such mixers. Novel thermal isolation of the journals for the two rotors separates their bearing assemblies from the severe heat being generated during mixing of plastic materials by continuous rotation of the two rotors within the mixer barrel. Localized cooling provides heat sinks for the drive and driven journals of each rotor. The rotors are shown as three-piece assemblies with drive and driven journals separate from the main rotor body. Beneficial interactions of localized cooling for the drive and driven journals plus thermal isolation of the journals from the severe heat being generated in the mixer barrel advantageously enables the journal bearing assemblies to be lubricated by grease instead of by circulating oil. Each of the journal bearing assemblies shown and described comprises two axially spaced, spherical-type roller bearings each encircling a portion of a journal and each being equipped with a seal housing having a grease fitting. The outer races of these roller bearings are shown and described as mounted in respective end frames which are spaced farther away from the upstream and downstream ends of the mixer barrel than their usual spacing in the past.