Oki Electric Industry Co., Ltd.

Oki Data Corporation

Oki Electric Co., Ltd.

Kuniharu Hayashi

Hiroshi Kikuchi

Masanori Maekawa

Minoru Mizutani

Jiro Tanuma

Takashi Itaya

Toru Ishihara

Masamitsu Nagamine

Hiroyuki Yajima

Kazuyoshi Yoshida

Yukio Ota

Tsutomu Yamane

Kazuhiko Nagaoka

Shyoichi Watanabe

Yoshitatsu Okiyama

Koichi Matsuzaki

Syuichiro Ogata

Tatsuya Murakami

Minoru Isobe

Shinichi Katakura

Toshiyuki Sato

Takao Uchida

Chihiro Komori

Hiroshi Sakaino

Koji Aida

Kazuki Obara

Toshihiro Nakano

Shoichi Watanabe

Naoki Chiba

An image forming apparatus has a fixing unit. A heat roller heats a toner image on a print medium to fuse the toner image. A first temperature detector is in contact with a longitudinal end portion of the heat roller, and generates a first temperature data. A second temperature detector opposes the heat roller and is in proximity to a substantially middle portion of the heat roller. The second temperature detector generates a second temperature data. Depending on the first temperature data and the second temperature data, a controller performs temperature control either in a first mode where the heater is energized such that the first temperature data is equal to a first target value, or in a second mode where the heater is energized such that second temperature data is equal to a second target value.

Image forming apparatus

A developing roller rotates in contact with a photoreceptor drum. The developing roller controls a development thorough the formation of a toner layer 50 .mu.m or less in thickness on an outer surface. The photoreceptor drum transfers a toner image formed on the outer surface by the controlled-development onto a medium. A fixation device heat-treats and fixes the toner image transferred onto the medium. A toner for the developing treatment comprises a resin having a Tg of 75.degree. C. or more as at least part of it.

Electrophotographic imaging apparatus using multi-layered toner

An electrophotographic printing apparatus has two charging bodies that are held at different potentials. The first charging body makes contact with the surface of a photosensitive drum; the second charging body makes contact with the first charging body. Toner particles that have acquired an electrostatic charge opposite to their normal charge are attracted from the drum surface to the first charging body. These toner particles are then attracted from the first charging body to the second charging body, whereby the first charging body is kept clean and able to charge the surface of the photosensitive drum to a uniform potential.

Electrophotographic printing apparatus with two charging bodies

A method of forming an electrostatic latent image includes printing operation and toner recovering operation. The printing operation includes charging, forming an electrostatic latent image, developing, and transferring operations. The toner recovering operation includes the step of charging the photosensitive drum in timed relation to the rotation of the photosensitive drum after printing operation so that reversely charged toner deposited on the charging roller migrates from the charging roller to the photosensitive drum. The toner migrated from the charging roller to the photosensitive drum is recovered into a developer. An apparatus for forming an image includes a charging roller, photosensitive drum, developing roller, and transfer roller. The apparatus further includes a reversely-charged-toner recovering device which causes the photosensitive drum to be charged in timed relation to the rotation of the photosensitive drum after printing operation so that the reversely charged toner deposited on the charging roller migrates to the photosensitive drum. The developer recovers the toner which has migrated to the photosensitive drum from the charging roller.

Method and apparatus for forming an electrostatic latent image with

The developing unit of an electrostatic printer is designed to avoid under-development of the bottom part of a dark latent image due to a reduction in recycled toner. This can be accomplished by providing the developing unit with one developing roller and at least two supply rollers. Alternatively, the developing unit has just one supply roller, but the rate at which toner is transferred from the supply roller to the developing roller can be switched. As another alternative, the supply roller and developing roller are designed to turn slowly enough that development of an entire page is completely developed before reaching the point where under-development would begin.

Developing unit for an electrophotographic printer employing a supply

A method of forming an electrostatic latent image includes printing operation and toner recovering operation. the printing operation includes charging, forming an electrostatic latent image, developing, and transferring operations. The toner recovering operation includes the step of charging the photosensitive drum in timed relation to the rotation of the photosensitive drum after printing operation so that reversely charged toner deposited on the charging roller migrates from the charging roller to the photosensitive drum. The toner migrated from the charging roller to the photosensitive drum is recovered into a developer. An apparatus for forming an image includes a charging roller, photosensitive drum, developing roller, and transfer roller. The apparatus further includes a reversely-charged-toner recovering device which causes the photosensitive drum to be charged in timed relation to the rotation of the photosensitive drum after printing operation so that the reversely charged toner deposited on the charging roller migrates to the photosensitive drum. The developer recovers the toner which has migrated to the photosensitive drum from the charging roller.

In a serial printer a pinion and a rack for lateral movement of a carriage, a dislodging member with edges proximate to the rack is provided to remove any chads or other foreign matters that may be attached to the rack, as they approach the pinion with the lateral movement of the carriage. The chads or other foreign matters are prevented from being caught between the pinion and the rack, and noises and increase in the torque due to the rolling in is prevented.

Rack and pinion cleaning mechanism in a serial printer

A permanent magnet type stepping motor comprising first and second stator assemblies arranged coaxially about a longitudinal axis. Each assembly includes first and second ring-shaped stators made of magnetic material. The first ring-shaped stator has a central portion with an opening therein, an annular yoke surrounding the periphery of the central portion and a plurality of pole pieces distributed about the circumference of the opening and extending toward a plane transverse to the axis. The second ring-shaped stator has a central portion with an opening therein, an annular substantially planar yoke surrounding the periphery of the central portion and a plurality of pole pieces distributed about the circumference of the opening and extending away from the transverse plane so as to interleave with the pole pieces of the first stator. The central portion of the second stator protrudes from the plane of the yoke in a direction away from the transverse plane. A coil is interposed between the first and second ring-shaped stators and surrounds the pole pieces. The first and second stator assemblies are arranged with respect to the transverse plane so that the second ring-shaped stator of the first stator assembly is adjacent the second ring-shaped stator of the second stator assembly at the transverse plane thereby forming a gap between the protruding central portions of the second stators of the first and second stator assemblies. A permanent magnet having N and S poles distributed alternately about the outer circumference thereof is rotatably supported within the openings in the central portions of the first and second stators of the first and second stator assemblies.

Permanent magnet type stepping motor

A ribbon protector is used for protecting paper from contamination by an ink ribbon in a printer, where the protector is inserted between paper located between a platen and a printing head. The printing head facing the platen performs spacing movement for printing. Two connected plate-like elements are provided with through openings for passage of the pin of the printing head. Mutually engageable electroconductive elements are provided on the inner walls of the two plate-like elements, at least in the area where they are compressed by the tip of the printing head, and spacers which are made from resilient materials are located between the two plate-like elements.

Ribbon protector including electro-conductive elements and platen gap

A stepping motor comprises a rotor assembly including a rotor shaft, a collar coaxially fixed to the rotor shaft, and a cylindrical permanent magnet block fixedly fitted on the collar, a yoke assembly including an inner yoke having a plurality of upper pole pieces arranged at regular angular intervals corresponding to an electrical angle of 2.pi. and a plurality of lower pole pieces arranged at regular angular intervals corresponding to an electrical angle of 2.pi., an upper outer yoke having pole pieces formed so as to extend between the upper pole pieces of the inner yoke, and a lower outer yoke having a plurality of pole pieces formed so as to extend between the lower pole pieces of the inner yoke, first and second driving coils received in a space defined by the inner yoke and the upper outer yoke and in a space defined by the inner yoke and the lower outer yoke, respectively, a base plate fixed to the upper end surface of the upper outer yoke, a flange fixed to the lower end surface of the lower outer yoke, and bearing bushes respectively provided in the central portions of the base plate and the flange to support the rotor shaft therein for rotation. The inner yoke is formed by bending the inner periphery of a single annular plate alternately in opposite directions to form the upper pole pieces and the lower pole pieces.

Stepping motor

In a method for operating a serial dot matrix printer having a print head that is reciprocated along a first direction and stopped for performing bi-directional printing on a medium that is moved in a second direction orthogonal to the first direction, correction amounts for correcting the bi-directional printing alignment are stored in a memory device. The desire correction amount is then selected and stored in a battery-backed-up memory. The bi-directional printing then is performed using the desired correction amount stored in the battery-backed-up memory.

Method for correcting bidirectional printing alignment of a serial dot

In a printer in which a printing medium is moved by a line-feed stepping motor during line-feed operation, and the line-feed stepping motor is stopped during printing operation and in a ready state, the line-feed stepping motor is caused to generate a first holding torque for preventing unwanted movement of the printing medium while permitting the operator to feed the printing medium manually, in the ready state of the printer, and the line-feed stepping motor is caused to generate a second holding torque which is greater than the first holding torque, during the printing operation.

Method of controlling a line-feed stepping motor in a printer and a

A carriage mechanism of a printer includes a carriage frame, a printed circuit board mounted on the carriage frame and having an exposed wiring portion and a plurality portion of guide holes, and a cable having at one end thereof an exposed wiring portion to be electrically connected to the exposed wiring portion of the printed circuit board. An inked ribbon feed mechanism has guide projections to be inserted into the guide holes and a plurality of elastic hooks for fastening to the carriage frame. A cable fixing mechanism includes a flexible film member to be superimposed over the end of the flexible cable and fixed thereto. One end of the flexible film member is shaped as the end of the flexible cable and the other end of the flexible film member is progressively narrower and projects toward a folded portion of the flexible cable.

Easily assembled carriage mechanism of printer

A printer includes a platen having a longitudinal axis and a printing head mounted in opposition to the platen. The guide shaft is mounted to extend parallel to the axis of the platen. A carriage supports the printing head and includes a carriage frame mounted on the guide shaft for movement axially therealong and for movement rotatably thereabout and a base plate having a first end integral with the carriage frame and a second end directed away therefrom. A guide plate is fixed at a position below the second end of the base plate and extends parallel to the guide shaft. A parallel link mechanism includes a fixing member attached to a lower surface of the second end of the base plate and a slider memebr connected to the fixing member. The slider member has a slot within which fits the guide plate, such that movement of the carriage axially of the guide shaft causes the parallel link mechanism and the second end of the base plate to be guided by the guide plate. An adjusting screw is threaded through a hole in the second end of the base plate and has a tip end in engagement with the slider member. Thus, upon rotation of the adjusting screw the slider member and the second end of the base plate are moved relatively toward or away from each other, thereby moving the carriage and the printing head rotatably about the guide shaft to increase or decrease the platen gap. A flexible member connects the slider member to the fixing member to prevent the slider member from becoming inclined relative to the guide plate.

Platen gap adjusting mechanism of printer

A carriage moving mechanism includes a carriage movably mounted on a guide shaft, a travelling motor fixedly mounted on the carriage, the travelling motor including a pinion mounted on a rotary shaft thereof, a rack provided in substantially parallel to the guide shaft, the rack being rigid longitudinally and flexible in a perpendicular direction to the longitudinal direction, the rack having longitudinally a tooth part engaged with the pinion, the surface of the rack located on the opposite side of the surface of the tooth part being substantially parallel to the guide shaft, a roller rotatably mounted on the carriage, the roller radially facing to the pinion and making contact with the opposite side surface to the tooth surface of the rack, the rack being rotatably mounted on the frame in one end thereof and restricted by the frame in the other end thereof in the extent of moving thereof or directly fixed on the frame in the other end thereof.

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Tokyo, Japan

Kuniharu Hayashi