| 摘要 |
PURPOSE:To make a printing condition always proper by holding the concn. of an additive to a predetermined value, by detecting the floating and sinking movement of a hydrometer arranged in supply water for use in printing by a photoelectric detector and controlling the injection amount of an additive to supply water by utilizing the obtained signal. CONSTITUTION:The supply water [in which an additive (alcohol) is contained in a predetermined concn.] 2 in a water tank 1 is recirculated through (i) a pipe 3, a water tray 4 and a pipe 6 or (ii) the pipe 3, a cock V, a detection tank 5 and a pipe 8. On the other hand, a hydrometer 10 is supported in the supply water 2 in the detection tank 5 in a freely floatable and sinkable manner through a guide 9 and a photoelectric detector PDT (a mark PS shows a light emitter and a mark PR shows a light receiver) is arranged in a freely settable manner in an up-and-down direction so as to be opposed to the cap 21 provided to the top. part of said hydrometer 10. In the above mentioned apparatus, when the concn. of the additive in the supply water 2 is lowered, the hydrometer 10 is sunk and a solenoid valve SV is opened by the signal from the photoelectric detector PDT detecting the sinking of said hydrometer 10 and the additive is injected into the detection tank 5 from a tank 7 and the concn. of the additive in the supply water is always held to a predetermined value. |
