Abstract: An electrophotographic digital copier for sequentially writing bicolor image data signals onto a photoconductive element and producing a bicolor hard copy by a single image transfer. The copier has a black developing device and a red developing device for developing respectively a latent image electrostatically formed by a black image data signal on a photoconductive element and a latent image electrostatically formed by a red image data signal. A signal detecting device determines whether or not the red image data is present. A control device starts the drive of the red developing device when the signal detecting device detects the red image data signal and ends the drive on upon the elapse of a predetermined period of time after the signal detecting device determines, during the driving of the red developing device that the red image data signal is absent.

Abstract: An electrophotographic color image forming apparatus is disclosed which allows a photoconductive element and an intermediate transfer belt, which are expendables, to be removed from the body thereof at the same time. This promotes easy replacement, inspection and so forth of expendables. The photoconductive element and intermediate transfer belt can be replaced substantially at the same period, reducing the frequency of replacement of expendables. A cartridge including the photoconductive element can be replaced with a minimum of component parts wasted, thereby enhancing the cost performance of the apparatus. Moreover, when a cover hinged to the body of the apparatus is opened, various units can be removed one after another, a unit around which the greatest space is available being first.

Abstract: An electrophotographic digital copier capable of identifying a particular color existing in a document image. The copier copies both of a bicolor document and a monocolor document in the same period of time. Even when monocolor documents and bicolor documents are to be copied together, the copier executes monocolor copy processing with the former and bicolor copy processing with the latter automatically.

Abstract: A copier, printer, facsimile apparatus or similar image forming apparatus made up of components each being constructed into a unit and connected to the others by external arrangements. The apparatus has a base unit accommodating an electric control device, a paper feeding unit removably mounted on the base unit, and an image forming unit for forming an image and recording it on a paper sheet. The base unit, paper feeding unit, and image forming unit may be combined in any desired configuration to construct an image recording apparatus capable of performing any desired kind of image forming procedure.

Abstract: A paper handling device for an image forming apparatus accurately positions paper sheets having been driven out of the apparatus with their center being in register with a reference at a predetermined position for executing stapling or similar processing. The device shifts the discharged paper sheets to a one-side reference position while truing them up at a center reference position. Therefore, the paper sheets are located at the one-side reference position with accuracy and thereby stapled or otherwise processed accurately. The device simplifies the movement of an instrument for implementing such processing. A stack of discharged sheets, whether they are so processed or not, can be readily taken out from the device with no regard to the paper size. A pair of paper guide members urge paper sheets in such a manner as to enhance further accurate positioning of the latter.

Abstract: A copying apparatus operable in a two-side copy mode has two exclusive switchback transport paths which are selectively usable for refeeding paper sheets each carrying an image on one side thereof from a refeed tray. One of the switchback transport paths is assigned to paper sheets of size A4 and smaller sizes which are fed sideways, while the other is assigned to paper sheets of sizes greater than A4.

Abstract: An extra data adding unit for an electrophotographic copier and others which allows date, time, page number, managerial number and other extra data, as distinguished from document data, to be copied together with an original document. The unit is provided with a thin flat configuration. A first display section for displaying extra data is provided on one surface of the unit while a second display section for monitoring the extra data and switches for setting modes and data are provided on the other surface of the unit. A battery for powering the unit is removably contained in the unit. That surface of the unit on which the monitor display section and switches are disposed is constituted by a white, light diffusing surface except for its area where the first display section is located. The position of the first display area is indicated on the other surface of the unit.

Abstract: First and second rectifiers (37), (41) have inputs connected to an A.C. power source (12) through a unitary switch (33) and outputs connected to first and second smoothing filters (38), (42) respectively. An inductance (39) is connected between the switch (33) and the first rectifier (37) whereas a capacitance (43) is connected between the switch (33) and the second rectifier (41). The values of the inductance (39) and capacitance (43) are selected in such a manner that surge currents through the capacitance (43) and inductance (39) occuring when the switch (33) is closed are limited and the power factor of the power supply (31) is maximized.

Abstract: In detecting the presence or absence of a developing agent or determining the residual amount thereof, at least one coil is arranged outside a developing agent container, so that a change in magnetic permeability caused by the presence or absence of a developing agent within the container or a change in the amount thereof can be detected as a change in the inductance of the coil.

Abstract: A flash tube is utilized as an imaging light source for a moving photoconductive belt or the like. A capacitor connected across the flash tube is charged from a power source. The flash tube is triggered when the voltage across the capacitor reaches a sufficient level to discharge the capacitor through the tube thereby firing the tube which emits an intense and brief flash of light for illuminating a document and imaging the photoconductive belt. A failure sensor produces a failure signal in response to a sheet jam or the like. A voltage comparator produces an enable signal when the voltage across the capacitor is sufficient to fire the flash tube. A trigger signal generator triggers the flash tube and shuts down the apparatus in response to the failure and enable signals in coincidence to discharge the capacitor and the photoconductive belt.

Abstract: A coil is provided to a developing tank containing a toner mixture consisting of ferromagnetic carrier particles and non-magnetic toner particles in such a manner as to be magnetically coupled with the mixture. The coil constitutes a frequency determining element of an oscillator. The inductance of the coil and thereby the frequency of the oscillator vary in accordance with the toner density or proportion of the toner particles in the mixture. An FM demodulator comprising a phase locked loop produces an output signal having a magnitude corresponding to the oscillator frequency and thereby the toner density. An electrically actuated valve is opened to supply more toner particles to the mixture when the toner density drops below a predetermined value.

Abstract: As a scanning element of an electrophotographic copying machine begins to move, a feed roller moves a sheet of copy paper into the bite of register rollers which are held stationary. This movement of the copy paper is accomplished in a period of time which is less than that required for the scanning element to reach a predetermined scan synchronizing point. The feed roller is then stopped so that the copy paper is slightly buckled and thereby resiliently urged into the bite of the register rollers. When the scanning element reaches the scan synchronizing point, a sensor causes the register rollers to rotate thereby feeding the copy sheet through the machine in synchronization with the movement of the scanning element. The copy machine may employ a seamless photoconductive drum or belt moving at constant speed in which case an electrostatic image is formed on the drum or belt by the scanning element. The image is developed by toner particles and transferred to the copy sheet.

Abstract: Timers measure the length of time for the leading edge of the first copy sheet to reach a sensing point at the discharge side of the machine after the copy operation is started and de-energize the machine if the measured time is longer than a predetermined time value, indicating that the first sheet jammed and did not reach the sensing point. If the first sheet reaches the sensing point in less than the predetermined time indicating proper feeding thereof, the length of time between the sensing of the leading edge and the trailing edge of the first sheet at the sensing point is measured, and the machine is deenergized if the measured time is longer than another predetermined value, indicating that the first sheet jammed at the sensing point.