WO1996031350A1 - Raclette, notamment pour serigraphie - Google Patents

Raclette, notamment pour serigraphie Download PDF

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Publication number
WO1996031350A1
WO1996031350A1 PCT/DE1996/000482 DE9600482W WO9631350A1 WO 1996031350 A1 WO1996031350 A1 WO 1996031350A1 DE 9600482 W DE9600482 W DE 9600482W WO 9631350 A1 WO9631350 A1 WO 9631350A1
Authority
WO
WIPO (PCT)
Prior art keywords
elastic part
doctor blade
soft
hard
squeegee
Prior art date
Application number
PCT/DE1996/000482
Other languages
German (de)
English (en)
Inventor
Rudolf August KÜRTEN
Original Assignee
Rk Siebdrucktechnik Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19516050A external-priority patent/DE19516050C2/de
Application filed by Rk Siebdrucktechnik Gmbh filed Critical Rk Siebdrucktechnik Gmbh
Priority to DE59603786T priority Critical patent/DE59603786D1/de
Priority to EP96905748A priority patent/EP0819060B1/fr
Publication of WO1996031350A1 publication Critical patent/WO1996031350A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41F—PRINTING MACHINES OR PRESSES
    • B41F15/00—Screen printers
    • B41F15/14—Details
    • B41F15/44—Squeegees or doctors

Definitions

  • the invention relates to a doctor blade, in particular for screen printing, in which the doctor blade and a printing screen are arranged such that they can be displaced relative to one another and the doctor blade is pressurized against the printing screen during the printing process, consisting of a soft elastic part with at least one doctor blade edge that can be placed against the printing screen and one hard elastic part that can be positioned on a squeegee holder.
  • Screen printing processes using a generic doctor blade can be carried out in such a way that the printing screen is arranged above a printing medium and is provided with a printing medium on its upper side.
  • the printing screen is brought into abutment against the printing medium and the printing medium is applied to the printing medium by means of its meshing while the pressure is being applied to the printing screen by pressing the squeegee.
  • a flat print image is thus generated by moving the doctor blade.
  • the squeegee can be arranged as fixed in screen printing and the printing screen, for. B. designed as a cylindrical rotary sieve, can be moved relative to the rack.
  • the soft elastic doctor blade material is subject to aging processes due to the absorption of solvents in the printing medium, which cause a change in the elasticity and can lead to the detachment of particles in the area of the doctor blade edge. In order to achieve a uniform doctor edge, it is then time-consuming and labor-intensive to dismantle and rework the doctor edge, as a result of which the screen printing machine has a long service life. Soft-elastic doctor blade materials are therefore used which are largely chemically inert to the solvents of the printing medium.
  • doctor edge is applied by exerting a pressure on the hard elastic part of the doctor against the printing screen.
  • spatially constant elastic properties of the hard elastic part of the doctor blade are necessary in order to ensure a uniform shape of the doctor blade edge over the entire length of the doctor blade.
  • the previously known plastic crochet blades which are produced by casting or centrifugal processes, meet these requirements only inadequately, since they have inhomogeneities which cause spatially different elastic properties of the doctor blade and which manifest themselves in an uneven print image.
  • doctor blades of different batches produced by means of the abovementioned methods have noticeably different elastic properties, so that when the doctor blade is changed, complex adjustment work on the screen printing machine is necessary in order to be able to reproduce the desired print image.
  • a generic doctor blade is described, for example, in DE 88 05 911 U, in which the doctor blade strip which can be placed against the printing screen is provided on the back with a support layer made of a plastic material which is harder than the material of the doctor blade strip.
  • the connection of the doctor blade strip to the support layer is expediently achieved in that the harder and the softer layer are brought together in a still reactive state and are bonded to one another by means of a chemical reaction.
  • the support layer and doctor strip are preferably made of a polyurethane elastomer.
  • DE 84 20 447 U also shows a generic doctor blade, in which the doctor blade profile, for example made of rubber or a thermoplastic, is inserted in a doctor blade holder made of a stable material such as metal.
  • the doctor blade profile is supported by a support profile made of a hard elastic material that laterally supports it and extends over its entire length.
  • the soft-elastic doctor blade profile is inserted into a slot in the doctor blade holder, which is made, for example, of metal, the above-mentioned disadvantages have to be accepted.
  • a generic doctor blade can also be found in JP abstract 2-206552 (A), which is produced in an injection molding process by injecting various materials into a hollow mold.
  • the materials of the doctor blade holder and of the doctor blade strip melt together, the material of the holder subsequently being cured with heat treatment.
  • a high degree of homogeneity and reproducibility of the doctor blade cannot be achieved in this way.
  • DE 84 23 641 U which goes back to the same applicant, shows a generic doctor blade in which a soft-elastic profile strip, preferably made of natural or synthetic rubber, is glued or welded to a support rail made of glass fiber reinforced polyester or steel.
  • the components of the doctor blade can also be connected in one piece during their manufacture.
  • the above-mentioned disadvantages could not be avoided with such a doctor blade.
  • a magnetic doctor device which has a profile strip arranged in front of the doctor roller and which has a support made of elastic, slidable material on the side facing the doctor roller, so that the doctor roller on the back the profile bar can be pressed and can be brought into contact with it to seal the application mass.
  • the soft elastic part and the hard elastic part of the doctor blade By means of the extrusion process used according to the invention for the production of the soft elastic part and the hard elastic part of the doctor blade, these parts can be produced for the first time in a homogeneity which has not been achieved using the casting or centrifugal processes previously used.
  • the soft-elastic part of the doctor blade can also be produced with precise shape without the need for complex mechanical processing by grinding or lapping processes.
  • an important step in the direction of a standardization of screen printing processes of the above-mentioned type is given, since there is no need for major adjustment work when changing the doctor blade.
  • the squeegee according to the invention can also be used in other printing processes, such as, for. B. gravure, can be used advantageously.
  • the soft-elastic part of the squeegee consists of a thermoplastic polyurethane elastomer and the hard-elastic part of the squeegee consists of polyolefin
  • the respective parts of the squeegee can be produced particularly homogeneously and precisely in a coextrusion process and meet the requirements set in a screen printing process especially with regard to chemical resistance.
  • Particularly satisfactory and reproducible printing results are obtained if the soft-elastic part of the doctor blade has a hardness of 75 to 95 Shore A and the hard-elastic part of the doctor blade has a hardness of 60 to 90 Shore D.
  • the hard elastic material can be filled, e.g. B. fiber reinforced.
  • the doctor blade has sufficient mechanical resistance even under the mechanical stresses to which it is exposed during the printing process if the soft elastic part and the hard elastic part consist of very different plastics, between which only negligible physicochemical binding forces act.
  • the plastics from which the respective parts of the doctor blade are to be manufactured can be selected so that they optimally meet the requirements placed on them with regard to chemical resistance, aging resistance and elasticity. Due to a close form fit, elastomers to be used in the squeegee can also be used for certain printing tasks, which would otherwise not be sufficiently securely attached to one another by means of an extrusion process or by using adhesives or the like.
  • the hard-elastic part of the doctor has at least one area which extends into the soft-elastic part and is provided with hook-shaped projections.
  • the person skilled in the art can form these projections in a variety of ways.
  • projections with a triangular, cross-shaped or star-shaped profile are conceivable, the regions of the hard elastic part also being able to extend in the direction of the squeegee edges.
  • the projections can also be designed as bends or the like, or a plurality of projections, for example arranged in a fan-like manner, can also be provided.
  • the hard-elastic part between the soft-elastic part arranged at its lower end and the hard-elastic part that can be positioned on the doctor holder at its upper end is essentially in the form of a strip.
  • the region of the hard elastic part extending into the soft elastic part of the doctor blade is arranged in the axial extension of the strip-shaped region, a mechanically particularly stable embodiment of a doctor blade is created, in which a favorable pressure transmission is given on the squeegee edge.
  • the hard-elastic part is provided with webs which extend transversely to the longitudinal direction of the doctor blade and substantially completely surround the soft-elastic part on the side facing the doctor blade holder, the webs having an angled area which at least partially surrounds the soft-elastic part on the side.
  • the hard-elastic part is advantageously flush on the outside with the soft-elastic part, which ensures a tight form fit and makes it more difficult to detach the soft-elastic part from the hard-elastic part.
  • the doctor blade can be provided with a plurality of doctor blade edges which have different profiles.
  • doctor blade is essentially mirror-symmetrical with respect to its longitudinal plane, the doctor blade is easy to handle and the doctor blade edge that can be placed against the printing screen can be exchanged for another doctor blade edge without great assembly effort.
  • the soft-elastic part can also surround the hard-elastic part on the outside at least over part of its height, as a result of which the elastic properties of the strip-shaped region holding the flexible part can be changed and adapted to different pressure conditions.
  • the soft-elastic part can extend to the upper end of the strip-shaped area, which can be arranged on the squeegee holder.
  • further soft-elastic parts can be arranged on the strip-shaped area, each of which is provided with one or more doctor edges.
  • a further soft-elastic part can be arranged on the strip-shaped area opposite the soft-elastic part arranged on the first narrow side thereof, this advantageously is so designed that it can be received by the doctor holder.
  • Doctor blades of the type described above produced in one piece in an extrusion process have clear advantages over previously known doctor blades in terms of their homogeneity and long-term stability even under high mechanical loads.
  • the plastic squeegee according to the invention can be produced in a coextrusion process in such a way that the hard-elastic part of the squeegee is extruded first, that after a cooling time in which the hard-elastic part has sufficient mechanical strength, the soft-elastic part of the squeegee is extruded with the hard elastic part to bring it into contact.
  • this also achieves a high dimensional accuracy of the parts and enables the parts to be profiled in the process steps following the extrusion process.
  • the hard-elastic part of the doctor blade is extruded with a region projecting laterally above the soft-elastic part, and after this subsequent extrusion of the soft-elastic part of the doctor blade, the still plastically deformable region of the hard-elastic part which projects laterally therefrom with permanent deformation with the soft-elastic part Part is brought to the plant.
  • the laterally projecting area of the hard elastic part can also be pressed laterally into the soft elastic part until it is flush with the soft elastic part on the outside of the doctor blade. In this case, the soft-elastic part is compressed and a tight form fit of the parts to one another is achieved.
  • a doctor blade is shown in cross-section, which has a soft elastic part 1 provided with two doctor blade edges and a hard elastic part 2 holding it with a positive fit.
  • the soft-elastic part 1 has an essentially pentagonal cross section, three of the outer boundary surfaces being arranged perpendicular to one another and having essentially the same edge lengths.
  • the base 3 of the soft elastic part 1 is laterally delimited by two doctor edges 4 and 5 which extend over the entire doctor length and which have a defined shape which remains the same over the entire doctor length.
  • the doctor blade edges are evenly curved and have a radius of 0.2 to 0.4 mm.
  • the doctor blade edges can of course also have a different shape, for example an irregularly curved or angular shape.
  • the hard-elastic part 2 of the doctor which carries the soft-elastic part 1, has at its upper end a holding area 6 which is widened in the shape of a head and which can be fastened to a doctor holder.
  • the holding area 6 can also be designed or provided with a soft-elastic part, so that with a suitable arrangement of the doctor blade in its holder, one of the soft-elastic parts of the doctor blade can be brought into contact with the printing screen.
  • the doctor blade edges can have different shapes.
  • the holding area 6 has a cavity 7 which extends in the longitudinal direction of the doctor blade and which enables the holding area to be deformed at least slightly and, owing to the reduced wall thickness, enables the holding area to be manufactured homogeneously and material inhomogeneities to occur during the process Cooling prevented.
  • the holding area 6 merges into a strip-shaped area 8, which has a reduced cross-section compared to the holding area 6, which is dimensioned such that, given material properties, there is sufficient flexural rigidity to transmit a corresponding force to the soft-elastic part 1 of the doctor blade enable.
  • a web 9 Arranged axially in extension to the strip-shaped area 8 is a web 9 which extends into the flexible part 1 and which ends in an anchor-shaped hook 10.
  • the strip-shaped area 8 also has two webs 11 arranged obliquely to it, which cover the side of the flexible part 1 facing away from the doctor edges 4 and 5 and thus the side of the flexible part 1 which faces away from the printing screen during the printing process.
  • the webs 11 have an angled region 12 which enclose the lateral boundary surfaces of the soft-elastic part 1 at their upper end.
  • the angled areas of the webs 11 are flush on their outer side with the soft elastic part 1, so that the narrow sides of the angled areas 12 are enclosed by the soft elastic part 1, as a result of which the hard elastic part 2 closes tightly with the soft elastic part 1 is guaranteed.
  • the holding lugs of the hook 10 point to the ends of the webs 11, so that the lateral boundary surfaces of the holding lugs face the doctor edges 4 and 5.
  • an area of the soft-elastic part 1 is almost completely enclosed in the upper region of the soft-elastic part 1 between the webs 11 and one retaining lug of the hook 10, as a result of the shrinkage of the soft-elastic part in the cooling downstream of the extrusion - a very tight form fit is achieved.
  • the area of the squeegee adjoining the squeegee edges 4 and 5 is made of soft elastic material, so that the squeegee on the printing screen deforms during the contact area Printing process a favorable geometry is created.
  • a different shape of the area of the hard elastic part 2 extending into the soft elastic part 1 influences not only the positive locking of these parts to one another, but also the course of the force lines in the pressurized contact area of the squeegee on the printing screen and thus the same Geometry.
  • the doctor blade according to the invention is produced in a coextrusion process in which the hard-elastic part 2 is extruded with regions of the webs 11 projecting laterally beyond the soft-elastic part 1.
  • the parts of the squeegee are brought into close positive engagement by subsequent deformation of the still deformable webs 11 of the hard elastic part 2.
  • the plastic shaping can take place in such a way that the entire width of the webs 11 is brought into contact with the soft-elastic part 1 or that only a partial area of the webs or the areas which are angled in the final state of the doctor blade with plastic deformation be brought into contact with the soft elastic part 1.
  • the time and the extent of the deformation of the hard elastic parts has to be adapted to the respective conditions and is essential both for the permanent connection of the parts as well as for the necessary manufacturing accuracy and homogeneity of the doctor blade.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Screen Printers (AREA)
  • Printing Plates And Materials Therefor (AREA)

Abstract

La présente invention concerne une raclette, notamment pour la sérigraphie, la raclette et l'écran étant disposés de manière à pouvoir être déplacés l'un par rapport à l'autre. La raclette est pressée contre l'écran pendant la phase d'impression. Elle est constituée d'au moins une partie très souple (1), avec au moins une bordure (4, 5) applicable contre l'écran, et une partie plus rigide (2) sur laquelle est montée la partie très souple (1) et qui se fixe sur un support. Selon l'invention, la partie très souple (1) et la partie plus rigide (2) de la raclette doivent être composées de matières plastiques coextrudées, la partie très souple (1) étant maintenue à la partie plus rigide (2) par les forces s'exerçant entre elles pendant la phase de coextrusion, de préférence par liaison de forme, de telle manière que les deux parties ne puissent pas se séparer dans les conditions caractéristiques du processus d'impression. La raclette ainsi obtenue offre l'avantage d'une plus grande homogénéité par rapport aux modèles classiques, aussi bien sur la zone d'impression que d'un lot à l'autre, et permet d'obtenir notamment une image d'impression très régulière. Elle implique un traitement moins important de la bordure de raclette et améliore considérablement la reproductibilité de la qualité de l'image d'impression.
PCT/DE1996/000482 1995-04-07 1996-03-15 Raclette, notamment pour serigraphie WO1996031350A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE59603786T DE59603786D1 (de) 1995-04-07 1996-03-15 Rakel insbesondere für den siebdruck
EP96905748A EP0819060B1 (fr) 1995-04-07 1996-03-15 Raclette, notamment pour serigraphie

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE19512697.1 1995-04-07
DE19512697 1995-04-07
DE19516050.9 1995-05-04
DE19516050A DE19516050C2 (de) 1995-04-07 1995-05-04 Rakel insbesondere für den Siebdruck

Publications (1)

Publication Number Publication Date
WO1996031350A1 true WO1996031350A1 (fr) 1996-10-10

Family

ID=26014130

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1996/000482 WO1996031350A1 (fr) 1995-04-07 1996-03-15 Raclette, notamment pour serigraphie

Country Status (4)

Country Link
EP (1) EP0819060B1 (fr)
AT (1) ATE187125T1 (fr)
ES (1) ES2141478T3 (fr)
WO (1) WO1996031350A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH376083A (de) * 1960-03-02 1964-03-31 Luescher Ag Geb Rakelhalter für Rakelgummi für Film- oder Siebdruck
CA1191306A (fr) * 1983-04-27 1985-08-06 George R. Mallory Lame de racloir
US4622712A (en) * 1983-11-07 1986-11-18 Toyoda Gosei Co., Ltd. Wiper blade rubber
EP0298911A2 (fr) * 1987-07-06 1989-01-11 Jürg Holderegger Dispositif de fixation d'une racle d'impression et/ou d'étalement d'encre
EP0576315A1 (fr) * 1992-06-05 1993-12-29 FIMOR (Société Anonyme) Porte-racle destiné notamment à une machine de sérigraphie
WO1994020339A1 (fr) * 1993-03-10 1994-09-15 Cooper Industries, Inc. Element protecteur profile pour lames d'essuie-glace

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH376083A (de) * 1960-03-02 1964-03-31 Luescher Ag Geb Rakelhalter für Rakelgummi für Film- oder Siebdruck
CA1191306A (fr) * 1983-04-27 1985-08-06 George R. Mallory Lame de racloir
US4622712A (en) * 1983-11-07 1986-11-18 Toyoda Gosei Co., Ltd. Wiper blade rubber
EP0298911A2 (fr) * 1987-07-06 1989-01-11 Jürg Holderegger Dispositif de fixation d'une racle d'impression et/ou d'étalement d'encre
EP0576315A1 (fr) * 1992-06-05 1993-12-29 FIMOR (Société Anonyme) Porte-racle destiné notamment à une machine de sérigraphie
WO1994020339A1 (fr) * 1993-03-10 1994-09-15 Cooper Industries, Inc. Element protecteur profile pour lames d'essuie-glace

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
S.H. MANNAN ET AL.: "Squeegee deformation Study in the Stencil Printing of Solder Pastes", IE.E.E. TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY: PART A., vol. 12, no. 3, September 1994 (1994-09-01), NJ US, pages 470 - 476, XP000462348 *

Also Published As

Publication number Publication date
ATE187125T1 (de) 1999-12-15
EP0819060B1 (fr) 1999-12-01
ES2141478T3 (es) 2000-03-16
EP0819060A1 (fr) 1998-01-21

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