| 摘要 |
<p>in a fluid metering system (10), a plunger actuated syringe (12) is coupled to at least one source of fluid, and a highly accurate friction drive (20) is coupled to the plunger for moving fluid to a delivery outlet. The friction drive comprises a rack (22) having a flat side (26) and a rotatable circular drive shaft, or pinion (24), pressed against the flat side (26) of the rack (22) for moving the same by friction. Opposed guide rollers (32, 34) engage the rack (22) in opposition to the flat side (26) in straddling relation with the pinion (24) for urging the rack (22) thereagainst. A movable swing arm (36) supports one of the guide rollers (34) against the rack (22). A spring (44) biasses the swing arm (36) and guide roller (34) against the rack (22) and transmits the force to the pinion (24). Means is provided for securing the swing arm (36) and the movable guide roller (34) in a plane perpendicular to the flat side (26) of the rack (22) to prevent lateral motion of the rack (22) and pinion (24) whereby inaccuracies in the system may be minimized.</p> |
