Patent ID: 6043862
Filing Date: 2000-03-28
Classification: G03D,G03G

Abstract:
A wet-type plate-making machine for producing a printing negative by developing and fixing a master sheet formed with a latent image, comprising:an exposure unit for forming a latent image by exposing image information on the master sheet by a laser beam;a developing unit including a concentration detection unit for detecting a toner concentration of a circulating developer, a developing tank having a liquid amount detection switch for detecting the liquid level of the circulating developer, a developer circulation pump, a developer refill pump, a toner refill pump, a developer bottle, a liquid toner bottle, and means for ejecting the developer containing liquid toner from a spray nozzle onto the surface of the master sheet thereby to develop said latent image;a fixing unit for fixing the developed image on said master sheet; anda control unit supplied with output signals from said concentration detection unit and said liquid amount detection switch for processing the output signals thereby to control said developer circulation pump, said developer refill pump and said toner refill pump;wherein said control unit includes means for determining whether or not the output signal from the liquid amount detection switch is included in a proper range, means for driving for a predetermined time said developer refill pump adapted to supply a new developer in said developing tank from said developer bottle when said output signal from the liquid amount detection switch assumes a value lower than a proper range, and means for transmitting an ""overflow alarm"" signal when said output signal from the liquid amount detection switch assumes a value higher than the proper range;wherein said control unit further includes means for transmitting a ""shortage alarm"" signal indicating that said developer bottle is empty when the output signal from said liquid amount detection switch fails to assume a value in a proper range after said developer refill pump is driven for a specified length of time.