Sheet feeding apparatus and image forming system

An image forming system comprising:

• an image forming apparatus that forms an image on envelopes;
• and
• a sheet feeding apparatus that feeds the envelopes to the image forming apparatus, wherein
• the sheet feeding apparatus includes:
• a stacking base arranged on an elevating plate, the stacking base having a stacking surface portion, wherein the stacking surface portion is an upper surface of the stacking base disposed vertically above the elevating plate,
• the stacking surface portion configured to support a stack of envelopes including a plurality of envelopes, the stacking surface portion being configured to support a center of the stack of envelopes such that sides of the envelopes extend laterally from the stacking surface portion in a width direction perpendicular to a conveying direction of the envelopes and the sides of the envelopes are unsupported;
• a sheet feeding roller configured to contact a topmost envelope arranged at a top of the plurality of envelopes in the vertical direction, and convey the topmost envelope;
• a curve forming member arranged on the stacking base, wherein the curve forming member is centered in the width direction with respect to the elevating plate and includes a pressing surface portion and a curve forming portion;
• the pressing surface portion is pressed by the sheet feeding roller via the envelopes, the pressing surface portion being mounted on top of the stacking surface portion or disposed below the stacking surface portion and being arranged at a downstream end of the s tacking surface portion;
• and
• the curve forming portion is arranged outside the sheet feeding roller in the width direction, that projects upward in the vertical direction above both the pressing surface portion and the stacking surface portion, and that supports the plurality of stacked envelopes.