Patent ID: 8763776

Claim:
A coupler for a viscometer bob shaft comprising: an upper assembly connected to an upper bob shaft; a lower assembly attached to a lower bob shaft; said lower assembly connectable to said upper assembly by at least one magnet provided in at least one of said upper assembly and said lower assembly and at least one magnet attracted material in said other of said upper assembly and said lower assembly; a rotation connection between said upper assembly and said lower assembly comprising at least one first face on said upper assembly and at least one second face on said lower assembly; said at least one first face proximate said at least one second face in a coupled orientation; said first face and said second face configured to cooperatively induce rotation of said upper assembly when said lower assembly is rotated; said coupler having a central rotation axis; said at least one first face comprising other than a cylindrical wall face coaxially aligned with said central rotation axis; and said at least one second face comprising other than a cylindrical wall face coaxially aligned with said central rotation axis.