placed around the peripheral surfaces of the photosensitive drum 11 referring to fig2 the process cartridge 15 is mounted in the image forming apparatus main assembly c to be used for image formation in an image forming operation a sheet s is fed out of a sheet cassette 6 mounted in the bottom portion of the image forming apparatus by a conveying roller 7 in synchronism with this feeding of the sheet s the peripheral surfaces of the photosensitive drum 11 is selectively exposed to a beam of light projected from an exposing apparatus 8 to form a latent image on the peripheral surfaces of the photosensitive drum 11 thereafter the toner stored in the toner contained 16 is coated in a thin layer on the peripheral surfaces of the development roller 18 by a development blade and development bias is applied to the development roller 18 as a result the toner is supplied to the peripheral surfaces of the photosensitive drum 11 in accordance with the latent image forming a toner image this toner image is transferred onto the sheet s which is being conveyed by the application of bias voltage to transfer roller 9 then the sheet s is further conveyed to a fixing apparatus 10 in which the toner image is fixed to the sheet s then the sheet s is discharged into a delivery portion 2 located on top of the apparatus main.