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 method for a charge control and multi-step deflection control type ink jet printer is disclosed which renders halftone by multi-step gradation. When an ink ejected from a nozzle is to be charged, a charging voltage is suitably varied to cause a shift in deflection by a pitch smaller than one dot pitch in the deflection direction, thereby selectively causing dots in the deflection direction to overlap and separate from each other. The pitch for developing the shift is variable to control the overlapping or separating degree of the dots in order to accomplish gradation in numerous densities.

Abstract: An ink level detector for use with an ink jet printer includes two electrodes for sensing changes in ink level inside an ink reservoir due to consumption. Fresh ink is supplied to the reservoir from an ink cartridge which is mounted in an upper wall of the reservoir. At least one of the two electrodes is positioned adjacent to a location where the cartridge is mounted to the upper wall of the reservoir.

Abstract: A control system for a charge deflection type ink jet printer which prints out one character line of print data by a plurality of strokes on a paper is disclosed. Data associated with odd scanning lines are printed out by one printing stroke of a carriage, then the paper is fed by a predetermined amount, and then data associated with even scanning lines are printed out. Thereafter, the paper is fed by an amount produced by subtracting a number of dots corresponding to a predetermined number of odd or even scanning lines from a number of dots corresponding to the total number of the odd and even scanning lines.

Abstract: A deflection control ink jet recording apparatus is capable of compensating for dislocation of dots at all the deflection steps. A deflection amount is adjusted with respect to two points to determine a correlationship between the amplification gain, charge code and deflection amount, so that an amplification gain and a charge code free from dislocation is set for each deflection step. A charge code compensation value is detected to add it to or subtract it from a predetermined charge code assigned to each deflection step, thereby setting a charge voltage code to be assigned to each deflection step in a printout operation.

Abstract: An ink jet head prints an image by superposing individual dot matrices of at least two colors. A computing unit receives electrical input signals representing the image and generates and feeds corresponding electrical signals representing the individual matrices of the at least two colors to the head means for printing. The computing means includes matrix generator means for generating the matrices in such a manner that the total number of dots to be printed in all of the matrices is limited to a first predetermined value which is less than the maximum possible total number of dots which can be printed in all of said individual dot matrices, and the total number of dots to be printed in the matrices which are formed by superposed dots of different colors is limited to a second predetermined value which is less than said first predetermined value.

Abstract: The present ink-jet printer is of the type in which ink droplets are charged under control and deflected by passing through an electric field, and it has two modes of operation: deflection error compensation mode and printing mode. In accordance with the present invention, deflection error is first compensated to determine an optimum amplification gain, which is then used in the printing operation, in which interactive effects with other ink droplets are compensated as well.

Abstract: An ink jet printing apparatus includes an ink condition detector for detecting a condition of ink. The ink condition detector produces outputs which represent a plurality of parameters of the ink. The parameters are the ink temperature, the ink pressure and the velocity of ink droplets in flight. A control device controls a charging device and/or a deflection device to compensate for a distortion in print position in accordance with an ink condition detected by the ink condition detector.

Abstract: An ink jet printing apparatus is disclosed in which part of ink droplets ejected from a nozzle of an ink ejection head and unused for printing purpose is caught by a gutter and returned to an ink supply source through an ink circulation path to be reused. The ink is partly shunted for disposal while fresh ink is supplied to the ink supply source in proportion to the amount of ink disposal, thereby maintaining the ink viscosity always at a proper value. For the disposal of the ink, a three-way solenoid operated valve is opened periodically for a predetermined period of time or, alternatively, ink droplets ejected from the nozzle are deflected to be caught by a gutter which is independent of the first gutter for routing to disposal means. The amount of disposal is determined by a pressure of ink fed to the nozzle and/or a temperature of ink in the neighborhood of the nozzle.

Abstract: An ink viscosity regulation apparatus for an ink jet printer is disclosed which controls the viscosity of ink to a value which lies within a range appropriate for printing. A signal commanding a supply of diluent into the ink is generated when a predetermined voltage level is exceeded by specific one of voltage levels for driving an electrostrictive vibrator of a head which causes a droplet to be separated from an ink stream at the shortest distance from the head.

Abstract: An ink jet printing apparatus is disclosed in which, upon an accidental change in the direction of ink ejection to an uncontrollable range caused by ink set in a nozzle of its head or dust particles deposited thereon, ink ejection from the nozzle is interrupted immediately to avoid electric discharge and other possible accidents. An alarm representing such a failure may be produced simultaneously with the interruption of ink ejection.

Abstract: An ink jet printing apparatus is disclosed in which ink drops are ejected sequentially from a head to print out dots on a recording medium. A predetermined number of guard drops are interpolated between adjacent printing drops. Guard drops selected out of the interpolated ones are charged to a same polarity as the printing drops and to a predetermined level, which is far lower than that for the printing drops. The charging is effected particularly on guard drops which lie in a high deflection step range.

Abstract: A print-distortion compensating apparatus and method for an improved electrostatic type ink jet printing apparatus including a print-distortion compensating means, in which the compensating amounts for the print-distortion due to the influence of the neighboring ink droplets, such print-distortion being variable depending on the respective deflection steps, for instance, the print-distortion caused by the variation of aerodynamic resistance due to the preceding ink droplets, the Coulomb's force due to the preceding and subsequent charged ink droplets, and the charge induction due to the preceding charged ink droplets are memorized into and read out from the afore-mentioned print-distortion compensating means and those are finally added to or not added to the basic charging codes depending on presence or absence of the PRINT data on the ink droplets adjacent to an ink droplet to be charged.

Abstract: In an ink jet printing apparatus wherein an ink ejection head is loaded on a carriage and, while the carriage moves relative to a sheet of paper, ink droplets are ejected from the head to be charged and deflected to impinge on the sheet of paper, a shape or a position of a conductive member carried on the carriage is varied to develop an electric field which is asymmetrical with respect to a predetermined plane in which charged ink droplets coming out from a charging electrode are to be deflected. The conductive member is constituted by a cover of the carriage, a shield plate, a gutter, a compensating electrode plate, a deflection electrode or the like.

Abstract: Depending upon a position in a dot matrix where an ink drop is to be deposited, the velocity imparted to that ink drop is controlled. The ink drop is charged by a charge electrode impressed with a constant charging voltage and deflected by a pair of electrodes impressed with a constant deflection voltage so as to be placed at an given point.

Abstract: In an electrostatic type ink-jet printer of the type leaving "guard drops" between charged drops, an electronic circuit is provided which generates charge-enabling signals in response to which guard drops are charged. When a sync signal is generated which synchronizes the rotation of a rotary drum with a print signal, one of the charge-enabling signals which is timed to charge an ink drop causes this ink drop to be charged. As compared with the prior art, ink dot misplacement due to the out-of-synchronization which in turn is due to the variations in rotation of the rotary drum can be more finely corrected. In addition, ink dot misplacement can be more precisely corrected by controlling the charge on an ink drop by pulses which have divided periods of that of the sync signals and which are synchronized with the sync signals.

Abstract: A drum (13) is provided with vacuum openings (14), (16), for suckingly holding a sheet (19) thereto for printing or the like. A sheet feed failure is detected by sensing for a drop in the level of vacuum at a vacuum source (12) below a predetermined value. Several regulators (36), (37), (38), (39) are provided for regulation to selected levels of vacuum.

Abstract: In an ink jet printer of the type wherein an ink jet nozzle continuously ejects the train of ink droplets and only ink droplets which are directed towards a recording surface are electrically charged and deflected by a pair of deflection electrodes so as to dot-form a character, a pair of auxiliary or compensation electrodes are provided in order to eliminate or control the inclination relative to the vertical line of dot-formed characters due to the relative speed between the recording surface and the ink jet nozzle.

Abstract: In an ink jet printing device wherein when a number of n nozzles are sequentially arranged in the direction of transport of recording paper and spaced apart from each other by a distance corresponding to m characters or ink dots so that when ink dots discharged from each nozzle are arranged in one column on the recording paper in the direction of transport thereof, the adjacent ink dots have a very small spacing, but they are nearly in contact with each other, a modulo-m address counter is stepped so as to store data in a memory while a modulo-n address counter is stepped to read out data. Thus positional deviations between nozzles may be compensated.

Abstract: An ink jet is ejected from an ink jet head (1.sub.1) at a constant frequency of pressure oscillation and separates into ink droplets at a certain position. A pulsating electric field is applied to the droplets at the separation position to charge the same where it is desired to print a dot on a sheet (PR), the charged droplets being electrostatically deflected onto the sheet (PR), whereas uncharged droplets are trapped by a gutter (GA). The phase of the pressure oscillation is initially progressively shifted until a charge detector (21) detects a charged condition of the droplets and then latched at that phase. A single charging electrode (41) and a single charge detecting electrode (21) may be used for several ink jet heads (1.sub.1, 1.sub.2, 1.sub.3) if a separate phase of charging voltage is provided for each respective ink jet head (1.sub.1, 1.sub.2, 1.sub.3) and the phases are alternatingly applied.