Sheet feeder capable of eliminating overlapping sheet feed

An image forming device comprising:

• a casing having at least one cassette accommodating section;
• at least one cassette maintaining a stack of sheets and detachably mounted on the at least one cassette accommodating section;
• a sheet feeder provided immediately downstream of the at least one cassette, the sheet feeder comprising;
• a feed roller comprising a roller mass having an outer circumferential surface contactable with a sheet from the stack of sheets of recording medium at a predetermined rotational phase of the roller mass and out of contact from the sheet at a second rotational phase other than the predetermined rotational phase;
• a separating pad opposing the feed roller and urged, by urging means for supplying an urging force, toward the feed roller for interposing the sheet between the separating pad and feed roller;
• and
• a space forming member having a contact portion contacting the sheet and the separating pad for forming a space between the circumferential surface of the roller mass and the sheet and between the circumferential surface and the separating pad against the urging force of the separating pad when the roller mass is in the second rotational phase, the contact portion of the space forming member contacting the sheet, when the roller mass is in the second rotational phase, at a same level at which the roller mass is in the predetermined rotational phase;
• a pair of guide rollers provided immediately downstream of the sheet feeder for conveying each sheet fed by the sheet feeder;
• an image forming unit positioned downstream of the pair of guide rollers for forming a toner image on the sheet fed by the pair of guide rollers, the image forming unit comprising a photosensitive drum and a transfer roller in confronting relation to the photosensitive drum;
• and
• a fixing unit positioned downstream of the image forming unit for fixing the toner image on the sheet fed from the image forming unit, the fixing unit comprising a heat roller and a pressure roller in contact with the heat roller.

A sheet feeder for feeding each sheet of recording medium, comprising:

• a feed roller comprising a roller mass having an outer circumferential surface contactable with the sheet of recording medium at a predetermined rotational phase of the roller mass and out of contact from the sheet at a second rotational phase other than the predetermined rotational phase;
• a separating pad opposing the feed roller and urged, by urging means for supplying an urging force, toward the feed roller for interposing the sheet between the separating pad and feed roller;
• a space forming member having a cylindrical member having a cylindrical hollow space therein and a contact portion contacting the sheet and the separating pad for forming a space between the circumferential surface of the roller mass and the sheet and between the circumferential surface and the separating pad against the urging force of the separating pad when the roller mass is in the second rotational phase, the contact portion of the space forming member contacting the sheet, when the roller mass is in the second rotational phase at a level substantially the same as a level at which the roller mass is in the predetermined rotational phase;
• a roller shaft extending in an axial direction of the roller mass and protruding from the roller mass in the axial direction, the roller mass being rotatable about an axis of the roller shaft, the space forming member being provided rotatable over the roller shaft;
• and
• a support shaft extending through the cylindrical hollow space, wherein the support shaft is provided with an irregular shaft portion around which the cylindrical hollow space is disposed, the irregular shaft portion being provided with a first radius portion having a first radius and a second radius portion having a second radius slightly smaller than the first radius, and the first radius of the first radius portion being equivalent to a difference between the radius of the circumferential surface when the roller mass is in the predetermined rotational phase and a distance from the contact portion of the space forming member to an inner peripheral surface which defines the hollow space.

An image forming device, comprising:

• a casing having at least one cassette accommodating section;
• at least one cassette maintaining a stack of sheets and detachably mounted on the at least one cassette accommodating section;
• a sheet feeder provided immediately downstream of the at least one cassette, the sheet feeder comprising;
• a feed roller comprising a roller mass having an outer circumferential surface contactable with a sheet from the stack of sheets of recording medium at a predetermined rotational phase of the roller mass and out of contact from the sheet at a second rotational phase other than the predetermined rotational phase;
• a separating pad opposing the feed roller and urged, by urging means for supplying an urging force, toward the feed roller for interposing the sheet between the separating pad and feed roller;
• and
• a space forming member having a cylindrical member having a cylindrical hollow space therein and contact portion contacting the sheet and the separating pad for forming a space between the circumferential surface of the roller mass and the sheet and between the circumferential surface and the separating pad against the urging force of the separating pad when the roller mass is in the second rotational phase, the contact portion of the space forming member contacting the sheet, when the roller mass is in the second rotational phase, at a level substantially the same as a level at which the roller mass is in the predetermined rotational phase;
• a roller shaft extending in an axial direction of the roller mass and protruding from the roller mass in the axial direction, the roller mass being rotatable about an axis of the roller shaft, the space forming member being provided rotatable over the roller shaft;
• a support shaft extending through the cylindrical hollow space and disposed over the roller shaft, the space forming member being provided rotatable over the roller shaft, wherein the support shaft is provided with an irregular shaft portion around which the cylindrical hollow space is disposed, the irregular shaft portion being provided with a first radius portion having a first radius and a second radius portion having a second radius slightly smaller then the first radius, and the first radius of the first radius portion being equivalent to a difference between the radius of the circumferential surface when the roller mass is in the predetermined rotational phase and a distance from the contact portion of the space forming member to an inner peripheral surface which defines the hollow space;
• a pair of guide rollers provided immediately downstream of the sheet feeder for conveying each sheet fed by the sheet feeder;
• an image forming unit positioned downstream of the pair of guide rollers for forming a toner image on the sheet fed by the pair of guide rollers, the image forming unit comprising a photosensitive drum and a transfer roller in confronting relation to the photosensitive drum;
• and
• a fixing unit positioned downstream of the image forming unit for fixing the toner image on the sheet fed from the image forming unit, the fixing unit comprising a heat roller and a pressure roller in contact with the heat roller.