Patent ID: 7837447

Claim:
A chemistry analyzer precision pump, including: a) a pump block defining: i) a first pump chamber having a fluid port at a first end, an opening for a first piston at a second end, a first bushing mount area, and a first seal mount located between the opening and the port, wherein the first pump chamber has a conical head defined by a first conic surface, ii) a second pump chamber having a fluid port at a first end, an opening for a second piston at a second end, a second bushing mount area, and a second seal mount located between the opening and the port, wherein the first pump chamber has a larger diameter than does the second pump chamber, and wherein the second pump chamber has a conical head defined by a second conic surface, b) a first O-ring seal mounted at the first seal mount, c) a second O-ring seal mounted at the second seal mount, d) a first ceramic piston mounted to reciprocate in the first pump chamber, past the first O-ring seal, wherein the first piston has a conical head defined by a third conic surface that has an aperture that is substantially the same as an aperture of the first conic surface, whereby the conical head of the first piston mates with the conical head of the first pump chamber at the top of its stroke, e) a second ceramic piston mounted to reciprocate in the second pump chamber, past the second O-ring seal, wherein the first piston has a larger diameter than does the second piston, wherein the second piston has a conical head defined by a fourth conic surface that has an aperture that is substantially the same as an aperture of the second conic surface, whereby the conical head of the second piston mates with the conical head of the second pump chamber at the top of its stroke, f) a canine that connects an end of the first ceramic piston to an end of the second ceramic piston, g) a first circular spring included in the first O-ring seal and positioned to bias the first seal against the first piston, h) a second circular spring included in the second O-ring seal and positioned to bias the second seal against the second piston, i) a first bushing mounted in the first bushing mount area to constrain motion of the first piston, wherein a length of the first bushing along the direction of motion of the first piston is longer than a diameter of the first piston where it constrains the first piston, and j) a second bushing mounted in the second bushing mount area to constrain motion of the second piston, wherein a length of the second bushing along the direction of motion of the second piston is longer than a diameter of the second piston where it constrains the second piston.