Abstract: The film developing machine includes a tank containing developing fluid, to which a dosing device continually adds regenerating fluid received from a regenerating-fluid supply tank. To prevent the gradual emptying of the supply tank from producing an accuracy-reducing gradual decrease in the pressure applied to the input side of the dosing device, the latter is connected to the supply tank via a buffer vessel provided with an internal valve mechanism serving automatically to keep the volume of regenerating fluid in the buffer vessel substantially constant despite variations in the amount of regenerating fluid contained in the supply tank.

Abstract: Fluid is withdrawn from plural fluid-filled tanks via respective outflow conduits leading into a common mixing conduit which includes a mixing pump, and then branches off through respective inflow conduits for return of intermixed fluid back to the individual tanks. Each inflow conduit is provided with a valve unit comprising a vessel-like housing having an inlet port and an outlet port. The flow from the inlet port to the outlet port is regulated in dependence upon the height of fluid in the respective tank. The fluid height is sensed indirectly by sensing the height or pressure of fluid in the interior of the vessel-like housing, the latter being at least partly lower than the height of fluid in the respective tank. Thus, the return of fluid into each tank is regulated to maintain a respective fluid height therein independently of the other tanks.