Hitachi Koki Co., Ltd.

Hitachi, Ltd.

Other

Yasuo Kikuchi

Toshitaka Ogawa

Tomio Sugaya

Isao Nakajima

Masayasu Anzai

Takashi Suzuki

Tsukasa Onose

Katsuhiro Akinaga

Shinya Kobayashi

Hiroshi Ueno

Shigenobu Katagiri

Koji Doi

Minoru Seino

Osamu Namikawa

Akira Arimoto

Akio Mukoh

Teruaki Mitsuya

Takao Umeda

Hirosada Morishita

Hiroyuki Mabuchi

Yasuo Takuma

Tatsuo Igawa

Takao Kumasaka

Yasuyuki Tsuji

Kunitomo Takahashi

Kunio Sato

Kazuyoshi Tokunaga

Masato Miwa

Akira Terakado

Shigeo Nemoto

Yosuke Saito

Kazuo Sakaki

Junzi Shirakawa

Motoji Kurobane

Masaaki Akutsu

Yousuke Saito

Hirobumi Ouchi

Kiyomi Tsuchiya

Sigenobu Katagiri

Syuho Yokokawa

Shinichi Fukazawa

In order to provide a miniature full-color recorder having an excellent color reproducibility and to provide a full-color recorder having a wider color reproduction range beyond the range of subtraction color mixing of three primary colors, first and second potential split developing processes are continuously arranged for one recording medium.

Full-color recorder using potential split developing process

A printer control system for controlling a print characteristic of a printer for printing a print pixel signal synchronized to horizontal lines of an image. The print pixel signal has an arbitrary horizontal resolution and includes white print pixel signals representing white pixels of the image and black print pixel signals representing black pixels of the image. The printer control system controls the print characteristic of the printer in accordance with a type of the image and includes a white enlarged line memory for receiving the print pixel signal and storing the print pixel signal at timing points spaced a predetermined time apart after expanding any portion of any white print pixel signal in the print pixel signal falling between two adjacent ones of the timing points and having a duration less than the predetermined time to have a duration equal to the predetermined time without expanding any portion of any black print pixel signal in the print pixel signal, and a black enlarged line memory for receiving the print pixel signal and storing the print pixel signal at timing points spaced a predetermined time apart after expanding any portion of any black print pixel signal in the print pixel signal falling between two adjacent ones of the timing points and having a duration less than the predetermined time to have a duration equal to the predetermined time without expanding any portion of any white print pixel signal in the print pixel signal.

Printer control system including white enlarged line memory for storing

In an image printer performing multi-color printing, two magnetic poles having the same polarity are provided adjacent to each other in a position facing the printing body of the second developing agent holding body provided in the second developing unit, and development is performed under a condition satisfying the following formulas;

Image printer

An imaging apparatus such that residual toner on a transfer/conveyer mechanism such as a transfer belt and an intermediate transfer material is effectively removable. High-tension voltage opposite in magnetic polarity (plus) to the charged toner and a photosensitive drum is applied to a discharger 15 provided ahead of a drive member 12 for driving a transfer belt 6. The residual toner on the transfer belt 6 is removed by a brush 21, and the residual foreign substances come in contact with the photosensitive drum 1 and move onto the photosensitive drum 1 before a printing operation is started. The foreign substances are then removed by a photosensitive drum cleaner.

Imaging apparatus and method for cleaning transfer/conveyer means

A developing apparatus in which a stationary multipole permanent magnet is placed in a sleeve and in which development is performed by bringing a developer, which contains at least carrier and toner particles and is held on the periphery of a sleeve by use of the magnetic force of the multipole permanent magnet, into contact with a photo-conductive body owing to the rotation of the sleeve. For securing image density and for preventing the deposition of carrier onto the photo-conductive body, two magnetic pieces, each of which is arranged lengthwise in the direction of the axis thereof and which have the same polarity, are placed in a region in the multipole permanent magnet which faces the photo-conductive body in such a manner as to adjoin in the circumferential direction of said permanent magnet. This results in generation of the distribution of a magnetic field which has two peaks of magnetic force. The position at which the second one of the two peaks of the magnetic force is formed, downstream in the direction of rotation of the sleeve, is set at the nearest point between the photo-conductive body and the sleeve. Thereby, even when development is performed by bringing the developer into light contact with the photo-conductive body, the image density can be secured. Further, the carrier can be prevented from depositing on the photo-conductive body.

Developing apparatus for an electrophotographic machine

A first-side toner image 25 is formed on a photo receptor 2 and transferred on a dielectric belt 19. A second-side toner image 18 is formed on the photo receptor 2. The two toner images 25 and 18 are simultaneously transferred on both sides of a print paper 26, and fixed thereon by paired heat rolls 30 and 31.

Optional side multi-toner image forming apparatus using intermediate

A method of preventing colors from being mixed in a two-color image forming apparatus. The surface of a photoreceptor is uniformly charged. A first latent electrostatic image formed on the photoreceptor surface is developed with a one-component developer so as to form a first toner image. A second latent electrostatic image formed on the photoreceptor surface is developed with a two-component developer so as to form a second toner image. The first and second toner images are simultaneously transferred onto a recording medium. In a preferred embodiment, the one-component developer is a magnetic toner, while the two-component developer is the combination of a nonmagnetic toner and a magnetic carrier. The magnetic toner and the magnetic carrier are preferably powder made of substantially the same materials.

Method of preventing colors from being mixed for a two-color image

An apparatus for printing on opposite surfaces of a strip of printing paper using two electrophotographic printing units wherein each printing operation is of high quality and thermal damage to the printing is minimized. The apparatus includes a first electrophotographic printing unit for printing on the front surface of the printing paper, a buffer unit for temporarily holding the printing paper discharged outside of the first electrophotographic printing unit, a turn unit for turning over the printing paper, and a second electrophotographic printing unit for printing the reverse surface of the printing paper. A toner having a low melting temperature is employed for each of the first and second electrophotographic printing units so that developing treatment is conducted only with the aid of a heat roll but without any use of a preheating plate. A back-up roll adapted to cooperate with the heat roll is coated with a tetrafluoroethylene-based synthetic resin. The second electrophotographic printing unit is provided with a paper presser for squeezing the printing paper against a photosensitive drum only within the printing width range. A retract mechanism is operatively connected to the paper presser.

Apparatus for printing on opposite surfaces of a strip of printing paper

An electrophotographic printing apparatus with a pivotable paper buffer and a pivotable guide member which together, depending on their position in relation to each other, form either a loading configuration or a printing configuration. In the loading configuration, the pivoting end of the buffer is adjacent to the pivoting end of the pivotable guide member to form a horizontal path for the paper to travel between the photosensitive member and the fixing portion. In the printing configuration, the buffer pivots upward away from the guide member so that it is in a position to receive a paper sheet as it is fed by a tractor after being contacted by the photosensitive member.

Electrophotographic printing apparatus with pivotable paper buffer and

A method of operating an electrographic printing apparatus which employs a reversal development system with a two components developer wherein the bias voltage and the surface voltage are varied in synchronism with each other.

Method of operating electrophotographic printing apparatus

An electrophotographic printer in which toner is printed and fused and the paper thereafter folded and stacked. To avoid toner stick a blower blows cooling air between adjacent folded sheets. The blower may be mounted on a horizotnally slidable paper guide. The stacker table may be lowered so that the top of the stack is maintained at the same height or the blower may be moved vertically in response to the output of a sensor detecting the top of the folded stack.

Paper cooling apparatus for an electrophotographic printer

In a printing sheet conveying device in which a sheet bearing a toner image is passed through a heating roll and a pressure roll, and which has means for changing the right and left contact pressures of these rolls to correct the meandering movement of the sheet when conveyance of the sheet is started; in which when conveyance of the sheet is started, the contact pressure of the rolls is made higher on one of the right and left sides than on the other side, and in a predetermined period of time the contact pressures on both sides are made equal to each other.

Sheet meandering movement preventing method

A fixing roller used in an electrophotographic device includes a coupling with a drive key that engages an end of a pressing roll that contains a key groove. Disposed between the coupling and the end of the pressing roll is a spacing member. This spacing member decreases the rate at which the key groove and the drive key deteriorate when two fixing rollers are used as pair to fix toner on a printed page. The spacing member is made of plastic, a sintered metal alloy, or other material. Also, the spacing member is lubricated to further prevent friction and the key groove of the pressing roll is lined with an abrasion resistant material to further prevent deterioration of the drive key and the key groove.

Fixing unit for electrophotographic device

A laser printer with a thermal fixing unit comprises: a pair of heat and pressure rolls for pressing a sheet with a developed toner image therebetween to fix the toner image on the sheet; a web immersable with an oil; an oil coater for supplying the oil to the web and pressing the web against the heat roll at at least one point to make the web contact with the heat roll so that the oil is applied from the oil coater onto the surface of the heat roll through the web to thereby prevent occurrence of offset of the toner image; and at least one pressing member provided separately from the oil coater for locally urging the web against the heat roll, the pressing member being located on at least one of before and behind the oil coater.

Laser printer with thermal fixing of toner

An electrophotographic device has a photosensitive element, an electrifier that forms a uniform electrostatic potential on the photosensitive element, and a light source for irradiating the photosensitive element to obtain an electrostatic latent image that has a reduced potential. A bias potential is applied to the photosensitive element after the latent image is formed, but before it is developed, so that the reduced potential of the latent image can be maintained at a constant level. With constant potentials existing on the photosensitive element, a printed image of high quality is obtained.

Growing community of inventors

Ibaraki, Japan

Yasuo Kikuchi