The present invention relates to a stencil printing apparatus and particularly to a stencil printing drum.
A conventional stencil printing drum structure includes a cylindrical drum having an ink-permeable region, an ink supply roller arranged in the drum so as to be in contact with the inner surface of the drum, and an ink application roller for supplying ink to the ink supply roller. The ink supply roller is arranged so as to rotate around an axis parallel to the center axis of the drum and come into contact with the inner circumferential surface of the drum. The ink application roller is disposed in parallel to the ink supply roller to form an ink reservoir portion between the ink application roller and the ink supply roller so as to apply ink onto the surface of the ink supply roller as the ink supply roller rotates.
Of the ink supplied to the inner circumferential surface of the drum by the ink supply roller, ink leaked out of the opposite ends of the ink supply roller moves onto the inner circumferential surface of the drum. A spatula-shaped plate member is disposed in the inside of the drum so as to touch the inner circumferential surface of the drum, so that the aforementioned leaked-out ink is returned to the ink application surface corresponding to the ink supply roller in the inner circumferential surface of the drum by the plate member.
It is, however, difficult to set the pressure and angle of contact between the spatula-shaped plate member and the inner circumferential surface of the drum. It is difficult that all the leaked-out ink is returned to the ink application surface in the inner circumferential surface of the drum securely. There arises a problem that part of the leaked-out ink not caught by the spatula-shaped plate member is further leaked out of the printing drum to thereby stain a printing apparatus and sheets of printing paper with ink. There arises another problem that the spatula-shaped plate member is worn out because it always touches the inner circumferential surface of the rotating drum.