Mixer drive apparatus

Mixer drive apparatus, which provides gear reduction for driving the impeller shaft of the mixer. A drive shaft (22) from an electric motor (18) is parallel to the impeller shaft (34) which extends through a support collar of a housing where the collar has a hole therethrough into which the impeller shaft extends into the housing. A hub (38) is rotatably mounted on the outside of the housing (10) and carries a gear (42) which is coupled to a pinion on the motor drive shaft. A coupling (70) is attached to the hub and bridges the hole in the collar. The end of the impeller shaft is cantilevered and overhung from the coupling. A gap is defined between the impeller shaft and the inside surface of the support collar which is adapted to receive a seal assembly. The seal assembly (30) includes a retainer hub which captures a sleeve containing the seal structure in the gap between the coupling and the retainer. The seal sleeve (40) may readily be removed upon disassembly of the coupling, which has two sections defining a split ring which clamps the upper end of the impeller shaft, and has a thrust plate with a bolt therethrough into the end of the impeller shaft for axially adjusting the location of the shaft so as to bring the seal sleeve into engagement with the coupling for rotation therewith. A support collar on the impeller shift engages the retaining hub when the coupling releases the shaft for the removal and replacement of the seal sleeve assembly. A seal captured by the collar engages the retainer hub and provides a pressure seal to facilitate replacement of the seal sleeve when the mixer is used with a pressurized vessel.