| 摘要 |
A system for dispensing exact quantities of fluid into containers without dripping or foaming can be made from the combination of a controllable pump, a tube (preferably hydrophobic), and a nozzle usually made of elastomeric material with an orifice or slit such a duck bill valves commercially available. Forward pressure causes the slit to open, while elastic force causes it to close when pumping stops. An alternative embodiment is to use slits backed by small diameter screen to achieve a back pressure.
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