Riso Kagaku Corporation

Takashi Isozaki

Sadanao Okuda

Takahito Tojima

Ryuji Higa

Kenji Oshima

Manabu Iwamoto

Hiroyasu Kato

Morio Ohashi

Kenji Suzuki

To make the stencil printing at a stabilized density from the start of printing in a stencil printing where a plurality of kinds of inks different from each other in volatility and/or viscosity are used. Information representing the volatility and/or viscosity of ink is stored in a storage means of an ink container, while the stored information representing the volatility and/or viscosity of ink is read out, and at the same time, the ceasing time from interruption of printing to resumption of the same is measured, and the printing pressure is controlled according to the ceasing time and the information representing the volatility and/or viscosity of ink.

Stencil printing system with print pressure controlling means

Stencil printing system with rotational speed control of the print drum

In a thermal head control system for controlling heating energy to a thermal had perforating stencil material unrolled from a stencil material roll, the heating energy to a thermal head is controlled according to the surface condition of the stencil material. The residue of stencil material M in a stencil material roll is calculated by residue calculating means and the elapsed time of the stencil material roll from production thereof is obtained on the basis of date data on the date of production of the stencil roll. Further, kind data on the kind of stencil material stored in the storage portion is obtained and the heating energy is obtained on the basis of the residue, the elapsed time and the kind data. On the basis of this heating energy, the heating action of the thermal head is controlled.

Method and system for controlling thermal head and stencil material roll

By preventing a deformation of printing drum of a rotary stencil printing apparatus caused at the time of printing, uniform printed images can be printed even under conditions such as low temperature and high-speed printing and even using an apparatus provided with a large-sized drum. That is, the invention provides a method for stencil printing which comprises winding a perforated stencil sheet around the peripheral wall of a cylindrical printing drum having an ink permeable peripheral wall and rotating around its central axis, supplying an ink to the peripheral wall from the inside of the drum at the time of rotation of the drum, and pressing a printing paper to the outer surface of the peripheral wall of the drum to transfer the ink to the printing paper through the stencil sheet, wherein the peripheral wall of the drum has such a strength that the peripheral wall shows a stress of 0.75 kgf/cm,or more, preferably 1.4 kgf/cm,or more when it is deformed by 0.1 cm in a direction towards its central axis and viscosity of the ink is 330 Pa&bull;s or lower, preferably 150 Pa&bull;s or lower. An apparatus for carrying out the stencil printing is also provided.

Method and apparatus for stencil printing

A print image treatment device is formed of a supply device for holding an excess ink removing liquid, the excessive ink removing liquid not dissolving in a printing ink forming a print image and having a lower surface tension than that of the printing ink; a rotating contact member having an outer surface, on which the excessive ink removing liquid is supplied from the supply device; a facing member situated under the contact member for nipping and carrying a printing sheet between the contact member and the facing member, an excessive printing ink forming the print image on a printing sheet being transferred to the excessive printing ink removing liquid when the printing sheet contacts the contacting member; a cleaning device contacting the contact member for removing the excessive printing ink with the excessive ink removing liquid; and a separation device receiving the excessive ink removing liquid with the excessive printing ink. The excessive ink removing liquid is separated from the printing ink having been transferred from the printing sheet. The separation device includes a filter having the thickness and air-flow resistance indicated below:

Print image treatment device

A print image treatment device is formed of a contact member which is coated on the peripheral surface with an excessive ink removing liquid incompatible with printing ink for forming a print image and having a lower surface tension than the printing ink, and is rotated in a specific direction, a facing member which serves to bring the printed side of a printed paper into contact with the excessive ink removing liquid by feeding the printed paper nipped between the contact member and the facing member, a supply means for supplying the excessive ink removing liquid to the peripheral surface of the contact member, and a cleaning means which contacts the peripheral surface of the contact member. The angle of the cleaning means from the tangent line of the peripheral surface is within a range of 5 to 60 degrees.

A printed image after-processing apparatus includes a rotatable contact member coated with an excess ink removing liquid incompatible with a printing ink forming a printed image on a printing sheet and having a surface tension lower than that of the printing ink; a counter member having a surface roughness of 0.5 .mu.m or less, for feeding the printing sheet after printed between the counter member and the contact member to thereby make a printed surface of the printing sheet into contact with the contact member; a supplying device for supplying the excess ink removing liquid to the contact member; and a cleaning device contacting with the contact member.

Printed image after-processing apparatus

A printed image after-processing apparatus is formed of a contact member which is coated with an excess ink removing solution which is incompatible with the printing ink forming a printed image and has a lower surface tension than the printing ink, and driven to rotate the contact member having coefficient of dynamic friction with 1.5 or less; a counter member holding to convey printed paper between it and the contact member, to thereby bring the printed surface of the printed paper into contact with the excess ink removing solution on the contact surface: a supplying device for supplying the excess ink removing solution to the contact member; and a cleaning device which contacts the contact member.

Printing image after-processing apparatus

The print image device according to this invention is comprised of a rotatable member with an excessive ink removing liquid applied to the surface, which does not dissolve in a printing ink forming a print image and has a lower surface tension than that of the printing ink; a facing member for bringing a printed surface of a printed body into contact with the excessive ink removing liquid on the contact member by nipping and carrying the printed body having been printed between the contact member and the facing member; a supply device for supplying the excessive ink removing liquid to the contact member; and a cleaning device for removing the excessive ink removing liquid with the printing ink, sliding in contact with the contact member. Furthermore, a mixture of the excessive ink removing liquid and the printing ink is formed at an upstream position in the rotating direction, i.e. in a contact part formed by the contact member and cleaning means on the contact member, where the quantity of the excessive ink removing liquid is controlled to be larger than one third of that of the printing ink.

Disclosed is the print image treatment device formed of: a contact member on a surface of which an excessive ink removing liquid not dissolving in a printing ink forming a print image and having a lower surface tension than that of the printing ink is applied, the contact member being driven to rotate; a facing member for bringing a printed surface of a printing body into contact with the excessive ink removing liquid on the contact member by nipping and carrying the printing body having been printed between the contact member and the facing member; a supply device for supplying the excessive ink removing liquid to the contact member; and a cleaning device for removing an excessive ink with the excessive ink removing liquid. The nip width formed by the contact member and the facing member, which is defined as the dimension of the part with which the contact member and the facing member are in contact in the direction of the printing body being carried, is specified to be 0.5 mm or over.

The occurrence of offsetting and strike-through in a stencil printing device is prevented without creating any new problems, and the printing paper is allowed to be conveyed with a pair of rollers interposing the printing paper for a reliable paper ejection process. Printing paper P is passed through a nip between a contact roller 37 and a counter roller 39 opposing the contact roller 37, the outer circumferential surface of the contact roller being coated with a layer of excess ink removing liquid which does not dissolve with the printing ink forming the printed image and has smaller surface tension than the printing ink, and the contact between the excess ink removing liquid layer a of the contact roller 37 and the printed surface of the printing paper P causes the excess portion of the printing ink b deposited on the printed image of the printing paper to be transferred onto the excess ink removing liquid layer a so as to remove the excess ink from the printing paper P. The contact roller may be replaced with an endless contact belt 83.

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Amimachi, Japan

Takashi Isozaki