초록 ▼

A piston carrier supports an elongated, slender piston rod for reciprocation in a pump cylinder to pump fluid into and out of the cylinder. The piston rod is made of a material such as sapphire or zircon and has a diameter less than about ten millimeters, and the pump can provide flows of from about

A piston carrier supports an elongated, slender piston rod for reciprocation in a pump cylinder to pump fluid into and out of the cylinder. The piston rod is made of a material such as sapphire or zircon and has a diameter less than about ten millimeters, and the pump can provide flows of from about 50 nanoliters to about 250 microliters per minute at pressures of several hundred bars. A drive motor rotates a threaded screw and a drive nut of a drive system applies a linear drive force to the piston carrier. A ball and socket connection between the drive system and the piston carrier avoids the need for precise alignment to prevent breakage of the fragile piston. A magnet in the socket holds the ball in place and avoids the need for a spring or other mechanical holder. The socket also includes a ring of a low reluctance material surrounding the ball to increase the magnetic retention force.

대표청구항 ▼

What is claimed is: 1. A high pressure, low volume pump comprising: (a) a piston; (b) a piston holder, the piston holder having a first end and a second end disposed opposite the first end, wherein the piston is mounted to the first end of the piston holder and a ball is disposed on the second end

What is claimed is: 1. A high pressure, low volume pump comprising: (a) a piston; (b) a piston holder, the piston holder having a first end and a second end disposed opposite the first end, wherein the piston is mounted to the first end of the piston holder and a ball is disposed on the second end of the piston holder; and (c) a socket provided at an end of a piston drive system, the socket comprising (1) a base wall; (2) a side wall extending axially from the base wall, the side wall surrounding at least a part of the ball; and (3) a magnet held in the base wall, the magnet holding the ball in the socket using magnetic force. 2. The high pressure, low volume pump of claim 1, further comprising a ring disposed on an end of the side wall opposite the base wall, the ring made of low reluctance magnetic material. 3. The high pressure, low volume pump of claim 2, wherein the ring is made of soft iron. 4. The high pressure, low volume pump of claim 2, wherein the ring surrounds a central plane of the ball. 5. The high pressure, low volume pump of claim 1, wherein the piston has a diameter of less than about ten millimeters. 6. The high pressure, low volume pump of claim 5, wherein the piston has a diameter in the range of about one millimeter to about three millimeters. 7. The high pressure, low volume pump of claim 1, wherein the piston is made of crystalline material. 8. The high pressure, low volume pump of claim 7, wherein the piston is made of sapphire. 9. The high pressure, low volume pump of claim 1, wherein the piston is made of a mineral. 10. The high pressure, low volume pump of claim 9, wherein the piston is made of zircon. 11. The high pressure, low volume pump of claim 1, wherein the ball is made of ferrous material. 12. The high pressure, low volume pump of claim 1, wherein the magnet is made of a rare earth material. 13. The high pressure, low volume pump of claim 12, wherein the magnet is a neodymium-iron-boron magnet. 14. The high pressure, low volume pump of claim 1, further comprising a spacer disposed between the ball and the magnet. 15. The high pressure, low volume pump of claim 14, wherein the spacer is made of non-magnetic material. 16. The high pressure, low volume pump of claim 15, wherein the spacer is made of plastic. 17. A chromatography apparatus comprising a high pressure liquid chromatography system, the system comprising: (a) a piston; (b) a piston holder, the piston holder having a first end and a second end disposed opposite the first end, wherein the piston is mounted to the first end of the piston holder and a ball is disposed on the second end of the piston holder; (c) a piston drive system, the piston drive system comprising (1) a socket disposed at one end of the piston drive system, the socket comprising (i) a base wall; (ii) a side wall extending axially from the base wall, the side wall surrounding at least a part of the ball of the piston holder; and (iii) a magnet held in the base wall, the magnet holding the ball in the socket using magnetic force; (2) a hollow drive collar disposed on the base wall of the socket; (3) a drive screw received by the drive collar at an end of the drive collar opposite the socket; and (4) a threaded drive nut mounted within the drive collar wherein the threaded drive nut mates with the drive screw; and (d) a motor wherein the motor connects to the drive screw and rotates the drive screw thereby imparting linear motion to the piston drive system. 18. The system of claim 17, further comprising a ring disposed on an end of the side wall opposite the base wall, the ring made of low reluctance magnetic material. 19. The system of claim 18, wherein the ring is made of soft iron. 20. The system of claim 18, wherein the ring surrounds a central plane of the ball. 21. The system of claim 17, wherein the piston has a diameter of less than about ten millimeters. 22. The system of claim 21, wherein the piston has a diameter in the range of about one millimeter to about three millimeters. 23. The system of claim 17, wherein the piston is made of crystalline material. 24. The system of claim 23, wherein the piston is made of sapphire. 25. The system of claim 17, wherein the piston is made of a mineral. 26. The system of claim 25, wherein the piston is made of zircon. 27. The system of claim 17, wherein the ball is made of ferrous material. 28. The system of claim 17, wherein the magnet is made of a rare earth material. 29. The system of claim 28, wherein the magnet is a neodymium-iron-boron magnet. 30. The system of claim 17, further comprising a spacer disposed between the ball and the magnet. 31. The system of claim 30, wherein the spacer is made of non-magnetic material. 32. The system of claim 31, wherein the spacer is made of plastic.