Image forming apparatus having image transfer electrode contactable to transfer material

An image forming apparatus comprising:

• an photosensitive member for bearing a toner image, movable along an endless path;
• an original supporting platen for supporting an original;
• an illumination source for illuminating an original on said supporting platen;
• image forming means including charging means, an exposure optical system including a reciprocable part for directing a light image of the original on said supporting platen, developing means and transfer means, wherein the reciprocable part moves in a first direction, during an image formation, in which the light image is directed to said photosensitive member for image formation thereon and in a second direction, during non-image-formation, for returning the part;
• wherein said illumination source emits light both during the image formation and during the non-image-formation to direct the light image to said photosensitive member;
• a degree of charging by said charging means is switched depending on whether said apparatus in the image formation or in the non-image-formation so that the degree is lowered during the non-image-formation;
• and wherein a developing bias voltage in said developing means is switched depending on whether said apparatus is in the image formation or in the non-image-formation so that an image formed on said photosensitive member is not developed by the developing means during the non-image-formation.

An image forming apparatus comprising:

• an photosensitive member for bearing a toner image, movable along an endless path;
• an original supporting platen for supporting an original;
• an illumination source for illuminating an original on said supporting platen;
• image forming means including charging means, an exposure optical system including a reciprocable part for directing a light image of the original on said supporting platen, developing means and transfer means, wherein the reciprocable part moves in a first direction, during image formation, in which the light image is directed to said photosensitive member for image formation thereon and in a second direction, during non-image-formation, for returning the part;
• wherein said illumination source emits light both during the image formation and during the non-image-formation to direct the light image to said photosensitive member., a degree of charging by said charging means is switched depending on whether said apparatus in the image formation or in the non-image-formation so that the degree is lowered during the non-image-formation;
• and wherein a developing bias voltage in said developing means is switched depending on whether said apparatus is in the image formation or in the non-image-formation so that an image formed on said photosensitive member is not developed by the developing means during the non-image-formation;
• and
• wherein said transfer means is in the form of an electrode for pressing a transfer material to said photosensitive member, and the electrode is supplied with a bias voltage including a polarity opposite to that of toner in said developing means during transfer operation, and is supplied with a bias voltage including a polarity the same as that of the toner during the non-image-formation.

An image forming apparatus comprising:

• an photosensitive member for bearing a toner image, movable along an endless path;
• an original supporting platen for supporting an original;
• an illumination source for illuminating an original on said supporting platen;
• image forming means including charging means, an exposure optical system, including a reciprocable part for directing a light image of the original on said supporting platen, developing means and transfer means, wherein the reciprocable part moves in a first direction, during image formation, in which the light image is directed to said photosensitive member for image formation thereon and in a second direction, during non-image-formation, for returning the part;
• wherein said illumination source emits light both during the image formation and during the non-image-formation to direct the light image to said photosensitive member a degree of charging by said charging means is switched depending on whether said apparatus in the image formation or in the non-image-formation so that the degree is lowered during the non-image-formation;
• and wherein a developing bias voltage in said developing means is switched depending on whether said apparatus is in the image formation or in the non-image-formation so that an image formed on said photosensitive member is not developed by the developing means during the non-image-formation;
• and
• wherein said transfer means is in the form of an electrode for pressing a transfer material to said photosensitive member, and the electrode is supplied with a bias voltage including a polarity opposite to that of toner in said developing means during transfer operation, and is supplied with a bias voltage including a polarity the same as that of the toner, and a polarity of charge on said photosensitive member is maintained to be the same as in the image formation, during the non-image-formation.