| 摘要 |
PURPOSE:To constitute the titled device so that a liquid level in a supply piping does not go down so much even when a developing operation is not being executed, by providing a check valve having a fluid resistance, in the supply piping for supplying a developer to a developing head from a developer tank. CONSTITUTION:A check valve 10 is provided on the way of a supply piping 3 between a density detector 4 and a developing head 1. This check valve 10 gives a suitable resistance to a developer which goes toward the developing head 1 from a developer tank 2 and also prevents a counterflow. As for the check valve 10, usually valve bodies 14, 24 close a liquid passage by springs 15, 25, and accordingly, a flow of a liquid in the direction as indicated with an arrow B is prevented, but at the time of the liquid is supplied in the direction as indicated with an arrow A, the bodies 14, 24 are opened by its liquid pressure and passing of the liquid is allowed, and in that case, by an effect of the spring, a moderate fluid resistance can be given. This fluid resistance can be changed by adjusting the strength of the spring.
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