| 摘要 |
A liquid-dosing apparatus has a lower tube centered on an axis and having a lower end provided with a nozzle, an upper tube telescoping coaxially with the lower tube and defining therewith an axial passage extending upward from the nozzle, A supply for feeding the liquid to the passage in the upper tube, and a drive that vertically reciprocates one of the tubes axially relative to the other. Respective upper and lower annular bladders in the tubes can be pressurized to block the passage in the respective tube therewith and depressurized to unblock the passage in the respective tube. A controller connected to the drive and pressurizing system alternately pressurizes and depressurizes the bladders synchronously with vertical reciprocation of the one tube. These bladders are annular, hollow, and have inner peripheries that lie flush in the passage when the bladders are depressurized. In addition to the nozzle, tubes, and bladders are all of the same flow section and shape, whereby the passage is axially uniform.
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