Abstract: An image forming apparatus is provided with a developing device for developing a latent image formed on the surface of the photosensitive drum. The developing device includes a first developing unit for developing the latent image by use of a first color developing agent and a second developing unit for developing the latent image by use of a second color developing agent. The first and second developing units are selectively driven and devices for inserting/removing the first and second development units are also provided. The image forming apparatus has a selecting device for interrupting an image forming process which is in progress to automatically select an image forming process which uses the second developing unit.

Abstract: In an image forming apparatus such as an image reader printer according to the present invention, light is radiated onto an original image by a light source, and a projection image corresponding to the irradiated original image is displayed on a projection screen. Cursors for designating a predetermined region of the projection image corresponding to the predetermined region of the original image are slidably displayed. When the original image is to be copied, the original image irradiated with the radiation light from the light source is optically scanned by a pivot mirror, and the scanning light is shielded by a shutter of a shutter unit only for a predetermined period of time corresponding to the predetermined region designated by the cursors. The shutter is controlled by a controller in accordance with the count of pulse signals generated by a generator that generates the pulse signals having a predetermined period, and shields the scanning light.

Abstract: An image of a microfilm is projected on a screen by light emitted from a light source. A pair of cursors are provided on each of adjacent sides of the screen so that a desired area of the image displayed on the screen can be designated by moving the cursors. A rotary mirror for scanning the image of the microfilm is arranged between the microfilm and the screen. The image of the microfilm is guided to a photosensitive drum by the mirror. A shutter is located between the photosensitive drum and the mirror. By controlling the shutter and the light source in accordance with an area designated by the cursors, an image of the microfilm corresponding to the designated area can be formed on the photosensitive drum.

Abstract: An image forming apparatus is provided with a developing device for developing a latent image formed on the surface of a photosensitive drum. The developing device includes a first developing unit for developing the latent image by use of a first colon developing agent and a second developing unit for developing the latent image by use of a second colon developing agent. The first and second developing units are selectively driven and devices for inserting/removing the first and second development units are also provided. The inserting/removing device includes a handle on the developing unit having first and second hooks which are rotated by the handle to engage pins on the housing of the image-forming apparatus to lock the developing unit in operative relationship with the photosensitive drum.

Abstract: An image-forming apparatus is provided with a photosensitive drum rotatably located in a housing, and a developing device for developing the latent image formed on the surface of the photosensitive drum. A first developing unit of the developing device develops the latent image by a color developing agent. A second developing unit develops the latent image by a second black developing agent. The first and second developing units are alternatively driven by a switch provided on a control panel which is located on the housing. The first developing unit is in the form of a cartridge which can be removably set in the housing. A pair of positioning members are attached to the front and rear walls of the developing agent supply section of the first developing unit. Both end support portions of the handle are swingably mounted on the positioning members by supporting shafts, individually. Each support portion of the handle is fitted with a hook which can rock around its corresponding supporting shaft.

Abstract: An image-forming apparatus is provided with a photosensitive drum rotatably located in a housing, and a developing device for developing the latent image formed on the surface of the photosensitive drum. A first developing unit of the developing device develops the latent image by a first red developing agent. A second developing unit develops the latent image by a second black developing agent. The first and second developing units, each of which includes a developing roller and a magnet roll, are alternatively driven by a switch provided on a control panel which is located on the housing. The respective magnet rolls of the first and second developing units are allowed to rock through about 25 degrees each. As the magnet rolls rock within this range, magnetic brushes of the developing agents can be formed on the surfaces of the developing rollers, respectively, or removed therefrom.

Abstract: An image-forming apparatus is provided with a photosensitive drum rotatably located in a housing, and a developing device for developing the latent image formed on the surface of the photosensitive drum. A first developing unit of the developing device develops the latent image by a first red developing agent. A second developing unit develops the latent image by a second black developing agent. The first and second developing units are alernatively driven by a switch provided on a control panel which is located on the housing. A copy mode for black is automatically established when the power is turned on or if no operation is performed for a prescribed time after a foregoing copying operation, in a mode for any other color than black, is ended.

Abstract: In a copy machine with a variable copy magnification, light reflected from a document, which is exposed by an exposure lamp, is led to a photosensitive drum to form thereon a copy image of a predetermined size and also led to a photo detecting circuit to detect a density of the document and to control an amount of exposure. An exposure control circuit of the copy machine comprises a magnification setter for generating a magnification signal dependent on a magnification as selected, a control signal generating circuit for generating a control signal according to the magnification signal and the output signal from the photo detecting circuit and a power source circuit for applying a power voltage to the exposure lamp according to the control signal.

Abstract: A jam detector comprising a timer, a comparator for comparing time interval data preset in the timer with time interval data which indicates the time interval required for conveying a transfer paper sheet from a first position to a second position, an operation control device for computing updated time interval data to be reset in the timer, and a RAM for storing the computed data. When a plurality of transfer paper sheets are present along the conveyance path extending from the first position to the second position, the conveying time interval data of the first transfer paper sheet is set in the timer. When the first transfer paper sheet reaches the second position, conveying time for the second transfer paper sheet to reach from the first position to the current position is computed by utilizing the data preset in the timer. The conveying time for the second transfer paper sheet to reach from the current position to the second position is computed, and is reset in the timer.