Magnetic drive pump having polymeric bearings and encased magnets for pumping very low temperature fluids

A seal-less magnetic drive pump for pumping cryogenic fluid below about −150 degrees centigrade comprising:

• a housing having an intake opening and an exhaust opening formed therein;
• a back plate mounted within said housing;
• a rotatable shaft journaled in at least one ball bearing held in said backplate, said bearing comprising a stainless steel race, stainless steel balls and polymeric retainer comprised of PEEK;
• an impeller mounted to said first end of said rotatable shaft;
• a casing mounted to said second end of said shaft for rotation therewith and comprising a casing material having a first coefficient of thermal expansion at very low temperatures;
• a magnet mounted to said second end of said shaft within said casing, said magnet comprising a material sized for close tolerance fit within said casing at room temperature having a second coefficient of thermal expansion of said magnet less than said first coefficient of thermal expansion of said casing so that said casing is tighter on said magnet material at said very low temperature;
• and
• a second magnet positioned in close proximity to said housing to magnetically couple to said first magnet, said second magnet adapted for mounting to a motor for rotation of said second magnet by which said magnetically coupled first magnet is rotated.