Patent ID: 7823870

Claim:
An image forming apparatus that forms an image on a sheet, comprising: (a) a sheet feed tray on which a sheet is stacked; (b) a sheet detector which detects physical property or a position for each of sheets fed from the sheet feed tray; (c) an image forming section which forms an image on the basis of a detected result by the sheet detector; (d) a transfer section which transfers the image formed by the image forming section onto the sheet; (e) a common conveyance path through which the sheet fed from the sheet feed tray is conveyed from a registration roller to the transfer section; (f) a direct conveyance path through which the sheet is directly fed from the sheet feed tray to the common conveyance path; (g) a delay conveyance path in which the sheet after being branched from the direct conveyance path is joined to the common conveyance path, and is caused to delay in being fed from the sheet feed tray to the common sheet conveyance path; (h) a conveyance section which conveys the sheet fed from the sheet feed tray to the transfer section, and (i) a controller which controls the conveyance section to convey once the sheet fed from the sheet feed tray from the direct conveyance path to the delay conveyance path, and thereafter to convey to the common conveyance path; wherein when the sheet feed tray is a main body sheet feed tray provided in a main body of the image forming apparatus, the direct conveyance path corresponds to a main body conveyance path in which a sheet is directly fed from the main body sheet feed tray to the common conveyance path, and the delay conveyance path corresponds to a conveyance path in which a sheet is fed from an optional sheet feed tray that is connected to the main body of the image forming apparatus to the common conveyance path.