Patent ID: 7798484

Claim:
A sheet feeder comprising: a storing unit configured to store a plurality of sheets of recording medium; a retaining unit provided at an edge of the recording medium that is stored in the storing unit, and having an inclined surface that is inclined to a surface of the recording medium and a protrusion member that retains the edge of the recording medium as being protruded from the inclined surface to be in contact with the edge of the recording medium; a sheet feeding mechanism configured to convey the recording medium stored in the storing unit toward the retaining unit and feed the recording medium while extracting the recording medium one-by-one from the storing unit by friction between the edge of the recording medium and the inclined surface and by friction between the edge of the recording medium and the protrusion member; and a protrusion amount adjusting mechanism configured to adjust a protrusion amount of the protrusion member from the inclined surface, and maintain the protrusion member in a protruded state with respect to the inclined surface when the recording medium is being conveyed, wherein the protrusion amount adjusting mechanism includes: a variable pressing portion having: a presser end portion that presses an end portion of the protrusion member in a direction that the protrusion member protrudes from the inclined surface, the end portion being buried in the inclined surface; and a plurality of supported surfaces that is formed at a position opposite to the presser end portion and formed to be different in distance from the presser end portion with each other; and a variable support portion provided with a plurality of support protrusions that face with the supported surfaces and support the variable pressing portion while contacting with any one of the supported surfaces, wherein the protrusion amount adjusting mechanism adjusts the protrusion amount by displacing a relative position between the variable pressing portion and the variable support portion in a direction along the supported surfaces.