High pressure low volume pump

A high pressure low volume pump for high pressure liquid chromatography and the like comprising:

• a pumping section including a pump cylinder;
• passages for the flow of a pumped fluid into and out of said cylinder;
• a piston assembly including a piston reciprocally movable in said cylinder;
• said piston assembly including a piston holder supporting said piston at a first end of said piston holder;
• a motor;
• and
• a piston drive system connected between said motor and the second end of said piston holder for reciprocating said piston assembly in response to operation of said motor;
• said piston being an elongated slender rod having a diameter of less than about 10 millimeters;
• the interconnection of said drive system and said second end of said piston holder including a ball-and-socket-coupling with a spherical member pivotally received in a socket;
• said socket being cup-shaped with a base and a side wall at least partly surrounding said spherical member;
• said pump being characterized by:
• a magnet in said socket for holding said spherical member in said socket using magnetic force, said magnet being located in said base adjacent to said spherical member, and said socket further including a ring of low reluctance magnetic material supported in said side wall and surrounding said spherical member.