| 摘要 |
<p>A liquid metering unit comprises a conduit (40) of flexible material depending between first and second rotatable rollers (18, 20) each having first and second curved surfaces (36, 38) and first and second flat portions (32, 34). The rollers (18, 20) are driven in opposite directions so that their first curved surfaces (36) impinge upon the conduit (40), constricting it and causing it to move upwards along its longitudinal axis such that any liquid contained therein is expelled from its lower end (44). Continued rotation of the rollers presents the second flat portions (34) to the conduit (40) which is released and drops back to its original position. The conduit (40) is recharged with liquid from a reservoir connected to its upper end (42) by means of a vacuum source (46) selectively connectable to its lower end (44).</p> |
