1. Field of the Invention
The present invention relates to a photosensitive material processing apparatus for processing a photosensitive material and to a sealing structure of a processing section of the photosensitive material processing apparatus.
2. Description of the Related Art
A photosensitive material, for example, a lithographic presensitized printing plate (hereinafter referred to as a PS plate), undergoes developing processing by means of a lithographic presensitized printing plate processing apparatus (hereinafter referred to as a PS plate processor). In this PS plate processor, a PS plate having an image recorded thereon is immersed in developing solution contained in a developing tank while being transported through the developing tank, and non-image portions of the photosensitive layer of the PS plate are removed by a rubbing means such as a brush roller in the developing solution. A PS plate, which has completed this type of developing processing, is washed with washing water in the washing section (washing processing) and then undergoes a type of plate surface protection processing where the plate is coated with a gum solution in the desensitizing section (desensitizing processing).
Japanese Patent Application Laid-Open No. 6-295071 discloses a lithographic printing plate processing apparatus which includes a pair of transporting rollers provided in the vicinity of an inlet opening of the apparatus, and a pair of transporting rollers provided at an upstream side of an exit opening of a finishing section of the apparatus. A pair of blades which are mounted on the periphery of the exit opening contact the pair of transporting rollers provided in the vicinity of an inlet opening of the apparatus, and a pair of transporting rollers provided at an upstream side of an exit opening of a finishing section of the apparatus. The apparatus further includes a shutter for closing the exit opening when the apparatus is not operated. Accordingly, the introduction of ambient air into the apparatus is prevented and the evaporation of processing solution is decreased
In order to minimize the contact between carbon dioxide in the atmosphere and the developing solution, a plate-shaped floating cover is floated on the surface of the developing solution contained in the developing tank.
However, the air flowing from the PS plate processor insertion aperture to its discharge aperture cannot be cut off from the surface of the solution simply by floating a plate-shaped cover on the surface of the solution. Therefore, the surface of the developing solution, which is not covered by the floating cover, contacts with fresh carbon dioxide from the in-flow of air above the floating cover and deterioration of the developing solution is accelerated by the carbon dioxide gas. Moreover, because of evaporation of the water in the developing solution, the rate of replenishment of the developing solution increases.
In a conventional PS plate processor, a driving section, consisting of gears and the like for driving a brush roller and the like, is provided above the surface of the developing solution inside the developing tank, making the provision of a cut-off means for halting the flow of air above the solution more difficult. This has meant that further minimizing of the deterioration of the developing solution caused by carbon dioxide in the atmosphere has not been achievable.