Screw profile mud-packing preventing

An annular support structure for a machine with a shaft assembly including a shaft and a collar coupled around the shaft, the annular support structure comprising:

• a hub;
• a bore extending therethrough, the bore sized radially larger than the shaft assembly;
• an engaging surface located radially opposite from the;
• a front radial surface extending from the bore to the engaging surface;
• a back radial surface opposite from the front radial surface, the back radial surface extending from the bore to the engaging surface;
• and
• a annular protrusion extending radially inward from the hub and helically around the hub, the protrusion extending from adjacent the front radial surface.

A collar for a machine having a shaft and an annular support structure concentric with the shaft, the annular support structure including a hub, a bore extending therethrough, and a protrusion extending radially inward from the hub, the collar shaped annularly, the collar comprising:

• a collar radial outer surface sized radially smaller than the annular support structure;
• a collar outer annulus portion adjacent to the collar radial surface;
• a plurality of grooves located at the collar radial outer surface, the plurality of grooves extending from the collar outer annulus portion and having an open front opposite the collar outer annulus portion, the plurality of grooves spaced around the collar radial outer surface, the plurality of grooves oriented substantially perpendicular to the radial direction of the collar;
• and
• a collar bore located opposite the collar radial surface and sized to mate with the shaft.