| 摘要 |
A chemical dispensing system having its most important use in dispensing flowable developing and finishing chemicals upon exposed lithographic printing plates comprises a supply container for each of the chemicals positioned immediately above the dispensing station therefor, each supply container containing continuously moving stirring means for keeping the chemical continuously in motion to homogenize the same. A number of flexible, laterally spaced dispensing tubes extend downwardly from each supply container, and a flow control valve is provided for each tube which pinches it into a closed position at a point near the container so that the volume of liquid which remains in the tube between the tube pinch point and the container is relatively small. The pinch valve comprises a unique combination of adjusting screws, a pressure-applying member and a spring member to control the closing pressure on each dispensing tube and the limited degree to which the tube is released, to permit small accurately controlled amounts of chemical to be dispensed through the dispensing tube. The spring member, upon release of closing pressure on each tube springs out to shake loose and distribute any particles which have settled out in the tube, to avoid clogging and to homogenize the chemical involved when it flows through the valve.
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