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 intended to be part of a screen printing machine, or to be handled by an operator, for printing or transferring fluids or pastes, or other applications.
• scraper heads of the type comprising a scraper holder and a deformable scraper blade, extending longitudinally and rigidly associated with one another.
• Such known scraper heads are the subject of numerous variant embodiments. They are fixed to support means of the machine by means of screws, stirrups or other clamping or fixing members.
• the downward pressure must both:
• a metal counter scraper or according to the terminology of the "flood bar” profession grazes the sieve to re-coat it with ink that was pushed to an edge of the screen by the previous print.
• the scraper blade is traditionally made of rubber and typically has the shape of a rectangular parallelepiped, it is continuous, both longitudinally and transversely. It can also present, in its part in contact with the sieve, different profiles deemed more favorable for certain works.
• the scraper blade must simultaneously have characteristics which seem contradictory.
• the scraper blade must also be flexible enough to:
• the doctor blades are incorporated into machines.
• the doctor blade is intended for manual operation as it results from documents GB-A-2.175.850, US-A-4.102.266, FR-A-2.302.199, US-A-4.989.511 or that either incorporated into a machine, there is the problem of having a scraper blade having both the rigidity and the flexibility required, as explained above.
• Document US-A-5,345,862 provides in one embodiment that the scraper blade has two outer layers and a more rigid inner layer.
• Document EP-A-167,906 provides a support bar made of a hard elastic material inserted in the doctor blade holder, to which a profiled blade made of a flexible material is connected.
• the scraping support inevitably has uneven surfaces. During the scraping, the passage of the scraper blade causes vibrations due to these surface inequalities which both affect the quality of the printing and contribute to the fatigue of the machine including the scrapes.
• the surface unevenness affects the printing since the operating conditions, in particular the application pressure of the scraper blade, its angle of inclination, and even its contact with the support to be printed are variable. from one place to another of the surface to be printed.
• the invention therefore aims to remedy the drawbacks or limitations of the current scraper heads.
• the invention aims to solve the problems inherent in surface unevenness of the scraping supports.
• the invention relates to a doctor blade intended to be part of a screen printing machine, or to be handled by an operator, for printing or transferring fluids or pastes, or other applications, comprising a head, a base in the shape of a lip and at least one elastically deformable member connecting the head and the base, the flexibility of the doctor blade, at each point independent of its length, resulting from the combination of the inherent flexibility of the lip and the elasticity of the elastically deformable member, characterized in that the elastically deformable member is structurally discontinuous in at least one place in the longitudinal direction of the doctor blade and extends along several layers of springs spaced from one another.
• the elastically deformable organ is located on all, substantially all or only part of the Ion- scraper.
• the doctor blade comprises one or more elastically deformable members.
• the respective elasticities of the lip and of the elastically deformable member are different from each other.
• the body of the elastically deformable member is produced from either one or more elastically deformable wires, in particular metallic wires, arranged in spirals or in undulations, or from a cut sheet, to form a simple comb or double whose stiffness is adjustable by the transverse dimension of the turns, undulations, cuts, or by the characteristics of the constituent material, or by the spacing existing between the teeth of the comb.
• the teeth of the comb formed by the elastically deformable member individually exert pressure on each of the longitudinal sectors of the lip, thus made independent.
• the independent distribution of the pressure by the teeth of the comb of the member is completed by a sliding of the head in a doctor blade and the ac ⁇ tion of an inflatable sleeve.
• the elastically deformable member comprises several functional parts as regards the elasticity, situated along the longitudinal direction of the doctor blade, these functional parts being substantially independent of each other so as to be able to take account of the surface unevenness of the support. to be printed.
• the body of the elastically deformable member comprises at least one and in particular two wires arranged in spirals or in undulations, defined with the head and the base a deformable quadrilateral according to the pressure exerted by the doctor blade. on the print media.
• This deformable quadrilateral is either a deformable parallelogram so that the angle of inclination of the lip on the support to be printed is constant whatever the pressure of the doctor blade on the support to be printed, or a trapezium whose large base is situated towards the head and conversely the small base situated towards the base of the elastically deformable member, the angle of inclination then being deliberately modified with the pressure of the doctor blade on the support to be printed.
• the body of the elastically deformable member, the head and the base are either electrically conductive or associated flush, so as to ensure a certain electrical continuity between the lip and the doctor blade via the elastically deformable member so as to evacuate static electricity.
• the elastically deformable member can be made of plastic or metal, metal alloy, or in combination of plastic, metal, metal alloy. This matter is armed or not.
• the scraping lip itself is in the form of a strip in one or more layers, possibly profiled. Its main constituent material is chosen from the group comprising elastomers, rubbers, plastics or other equivalent materials, and in particular polyurethanes.
• This lip about 10 to 30 mm high and fixed resiliently to the elastically deformable member, is produced by casting, extrusion, machining or the like. If necessary, it conducts electricity so as to evacuate the static electricity developed during the scraping.
• the scraper lip comprises two parts, namely a core permanently fixed to the base of the elastically deformable member and an outer scraper part, preferably of low linear mass, fixed to the core. This attachment is removable, by clipping or otherwise.
• a doctor blade as just described may further include two screen lowerers at its two ends.
• the elastically deformable member can be sealed or closed, but preferably, it comprises at least over part of the length of the doctor blade a plurality of openings or bores above the lip allowing the passage of excess ink printing.
• the scraper lip of the doctor blade described may have a reduced transverse height, in particular of the order of a centimeter. This low height then allows the passage, over, of excess printing ink, in order to be able to use the doctor blade in both directions. For some appli ⁇ cations, this height can even be reduced to a simple steel wire with disappearance of the elastomer part.
• the elastically deformable member is in the general form either of a strip of substantially constant width, or of a sheet or strip comprising one or more cutouts or protrusions extending transversely, or of a comb or a spiral or wavy piece having projections extending in particular vertically.
• These protuberances or projections extend either over the same distance along the doctor blade, or over different distances depending in particular on the flexibility / hardness desired.
• Neighboring functional parts which are functionally sub ⁇ stantially independent of one another forming part of the elastically deformable member, in particular the protuberances or projections adjoin or adjoin each other sub-stantially or, on the contrary are spaced along the longitudinal direction of the doctor blade . If necessary, this spacing is variable depending on the flexibility / hardness desired.
• a ply along which an elastically deformable member extends is located between or outside but in the vicinity of the two planes externally limiting the scraper blade.
• an elastically deformable member is interposed between the head and the lip.
• the elastically deformable member forms the single member or the main member by which the lip is carried by the head.
• the head in general is relatively hard, about 60 ° Shore D and more, intended to be fixed in the manual or machine doctor blade and is about 10 to 30 mm high, preferably 12 to 18 mm.
• the upper parts of the elastically deformable members are rigidly fixed in or on the surface of the head.
• the doctor blade head slides freely in the doctor blade holder, an inflatable sleeve ensures a pressure equal to each point of the lip whatever the unevenness of the printing medium.
• the elastically deformable member and the scraping lip are placed substantially in extension of one another.
• the elastically deformable member is, at least in part, in the form of a part of the doctor blade head having a certain capacity for elastic deformation.
• the elastically deformable member has a different linear mass from that of the scraper blade proper, so as to have a very different vibration period than that of the lip, the combination of the lip and the elastically deformable member (s) does not not being likely to enter into resonance under normal conditions of implementation, during the scraping of a support having surface inequalities.
• the elastically deformable member is rigidly fixed to the head on the one hand and elastically to the lip on the other hand, by crimping, bonding, overmolding or the like. This association is carried out either with immobilization, or with a certain possibility of relative pivoting around an axis extending parallel to the length of the doctor blade.
• the elastically deformable member is functionally and / or structurally composite and comprises a rigid or substantially rigid head intended to be associated with the doctor blade holder, a semi-rigid base intended to be associated with a removable lip and, between the head and the base, a body essentially forming the elastically deformable member.
• the head and / or the base and / or the body are associated detachably or not.
• the body of the elastically deformable member is associated with the head and / or the lip in a removable manner by force or by means of fixing members such as clips.
• the head and base have a contoured shape.
• the scraping lip is associated or forms with the head and / or the base of the elastically deformable member an angle relative to the longitudinal axis of the doctor blade.
• the head has a profile allowing the installation on a doctor blade holder with several angles of inclination relative to the longitudinal axis of the doctor blade.
• the flexibility / hardness of the doctor blade can be adapted in all directions, in particular from top to bottom.
• doctor blade avoids "encplaning" at high speed, the edge of the lip no longer pitching the screen and the excess ink possibly being able, if it is sufficiently fluid, to be discharged over the upper edge of the lip.
• the printing may be faster, in particular back and forth.
• doctor blade makes it possible to optimize the ink flow and to control the hydraulic pressure and the quantity of ink deposited, independently of the speed of scraping.
• doctor blade makes it possible to control the angle of attack of the doctor blade regardless of the vertical bearing pressure exerted on the doctor lip. As required, with two substantially parallel plies of springs, this angle remains constant or, on the contrary, is modified positively as a function of the pressure exerted.
• a doctor blade according to the invention makes it possible to take advantage of the fact that the material constituting the elastically deformable member does not retain residual deformation, unlike the rubbers of conventional doctor blades.
• the doctor blade according to the invention allows the lip to conform exactly to the support to be printed, even if the latter has surface irregularities.
• the spacing variations can be adapted.
• a doctor blade according to the invention also makes it possible to transfer the pressure to the screen outside the printing area, which has the effect of extending the life of the constituent elements of the machine as well as of the screen used for printing. .
• a doctor blade as described has also reduced the total weight compared to a conventional doctor blade. This reduction in weight results in lower inertia which is favorable to the operation of the doctor blade.
• a doctor blade 2 is fixed to the doctor blade holder 1 by a screw 10. It can be seen that during bending, the angle a on the sieve 7, initially established around 75 °, rapidly decreases towards an angle ⁇ of 40 °. This occurs whether the doctor blade 2 has one or more layers.
• FIG. 2A representing a doctor blade 2 according to the invention, seen in profile, it can be seen that, by the effect of the deformable parallelobgram 4.1 and 4.2, the angle ⁇ formed by the lip 5 in work is equal to the initial angle at .
• FIG. 2B is a front view of different types of spring 4a, 4b and 4c which can constitute the double elastically deformable member 4.
• FIG. 3A represents an overlap of the turns of the spring 4 creating a flexible interdependence in the lip 5.
• FIG. 3C illustrates a mode of hardening of the doctor blade 2 by bringing the turns 6 together.
• FIG. 3E illustrates an adjustable angle doctor blade intended for old machines which do not have this adjustment.
• FIGS. 4A, B and C illustrate the variations in point hardness of a doctor blade 2 due to the variations in the spacing of the U-shaped pins constituting the elastic member.
• FIG. 4D represents the profile view of the same doctor blade. We notice the trapezoid shape.
• FIG. 5 illustrates the case where the elastically deformable member 4 is an extension of the head 3, in the present case a plastic profile.
• Sectors 4a, 4b and 4c illustrate the hardness setting by digging more or less deep slots 16.
• FIG. 6 represents a doctor blade 2, the deformable elastic member 4 of which is constituted either by a strip folded in a U 13 ′ or by two strips 13.
• a plastic profile constitutes the head 3 of the doctor blade 2, it is included in the U or pinched by the doctor blade 1 between the two strips.
• the front views illustrate two types of teeth, hollow or solid, of the elastically deformable member 4.
• FIG. 7A illustrates the passage of an ink 8 of low thixotropy in the openings 16 between the teeth of the comb constituting the elastically deformable member 4.
• the openings 16 are closed with an adhesive 17 to facilitate cleaning without weighing down the apparatus.
• FIG. 8 illustrates a doctor blade where the springs are molded over a large part of their height by a thin layer of rubber constituting the lip 5.
• the space 14 between the two plies of springs is either empty or filled with foam 15.
• the front view 8C illustrates, in exploded view, the different layers constituting the elastically deformable member 4 in the case of foam filling.
• Figure 9 illustrates a rectangular single-wire spiral construction, entirely included in the material constituting the lip 5. This assembly is suitable for doctor blades of small sections.
• FIGS. 10A, 10B, 11A and 11B are two pairs of diagrams illustrating the structure of a doctor blade whose elastically deformable member forms a quadrilateral and this in different possible embodiments, the pressure being greater in the case of FIGS. 10B and 11B than in the case of FIGS. 10A, and 11A; in Figure 11B the trapezoidal shape positively corrects the angle under vertical pressure.
• FIG. 12 also illustrates a variant embodiment of the doctor blade in which the doctor lip is in two parts, one of which is easily removable by clipping.
• FIGS. 13A, B and C illustrate a doctor blade whose head 3, which accepts longitudinal flexions, can slide vertically in the doctor blade holder 1, an inflatable sleeve 19 exerts a constant linear pressure downwards.
• the lower part 5 consists of a fixed core 23 and a removable lip 24.
• the doctor blade 2 is functionally and structurally composite and comprises a head 3, a lip 5 and an elastically deformable member 4.
• the head 3 is rigid or substantially rigid, it is intended functionally to be associated with the doctor blade 1.
• the member 4 is placed between the head 3 and the lip 5.
• the head 3 and the lip 5 have a profiled shape.
• the member 4 is also profiled, solid or perforated.
• Such a profiled shape allows the lip 5 to be associated or to form with the head 3 a certain angle ⁇ , ⁇ relative to the longitudinal plane of the doctor blade 2.
• the elastically deformable member 4 is, according to the embodiments considered, in the general form of either a strip, of substantially constant width, the profile of which, transversely can be more or less developed, or in the form of a strip comprising one or more slits or protrusions extending transversely, either under the shape of a comb or of a spiral or wavy piece, also having protrusions. These protrusions extend in particular transversely. According to other embodiments, they can be extended differently.
• protuberances or protrusions extend over the same distance, along the doctor blade or, on the contrary, over different distances, depending in particular on the flexibility / hardness desired.
• Such so-called functional parts in particular the protuberances or protrusions, either adjoin or substantially adjoin, or overlap, or are separated from the neighboring functional parts along the longitudinal direction of the doctor blade.
• This spacing is either constant or variable, depending in particular on the flexibility / hardness desired locally.
• doctor blade 2 rigidly removably associated with the doctor blade holder 1.
• the doctor blade 2 being in contact with the screen 7 has a head 3, a lip-shaped base 5 and at least one elastically deformable member 4 connecting the head 3 and the base 5.
• the assembly extends longitudinally along an axis. In operation, this axis is placed horizontally or substantially horizontally.
• the doctor blade holder 1 has a high overall rigidity and constitutes the carrier element of the doctor blade 2.
• the doctor blade 2 has on the contrary a certain deformability.
• the head 3 and the lip 5 of the doctor blade 2 are in the form of a strip in one or more layers of polyurethane than elastomer, each before 12 to 18 mm high, approx. ron, but different elasticities, with the head 3 being more rigid and the lip more flexible.
• the elastically deformable member 4 according to FIGS. 2 to 4 is produced from one or more elastically deformable wires arranged in undulation to form a single or double comb whose stiffness is adjustable by the transverse dimen ⁇ sion of the undulations 6, or by the characteristics of the constituent material, or by the spacing existing between the corrugations 6.
• a wire or cable 20 extends parallel to the length of the doctor blade 2 to create a certain flexible interdependence in the corrugations 6 towards the lip 5.
• the elastically deformable member 4 is structurally discontinuous in the longitudinal direction of the doctor blade 2 at at least one location, because of the succession of the wire forming the corrugations 6 and the space between the corrugations 6.
• structurally discontinuous is meant the fact that the elastically deformable member 4 is produced in such a way that a material or mechanical discontinuity is ensured along the doctor blade 2.
• the structural parts 6 constituting the elastically deformable member 4 are then or separated from each other.
• the doctor blade 2 comprises at least one elastically deformable member 4 located in at least one location of its length.
• the elastically deformable member 4 acts on the lip 5 so that the flexibility of the doctor blade 2 in the location where the member 4 is located results in combination from the inherent softness of the lip 5 and the elasticity of the elastically deformable member 4.
• the respective elasticities are different.
• the elastically deformable member 4 is located over the entire length of the doctor blade or over all of this length or over a portion only of this length.
• the elastically deformable member 4 is placed at the end parts of the doctor blade or, on the contrary, in its middle part.
• one or more elastically deformable members 4 may be provided located in combination over all or substantially the length of the doctor blade 2 or over only a part of it.
• the doctor blade 2 comprises either a single elastically deformable member, or several.
• the elastically deformable member 4 comprises, in the embodiment more particularly shown in FIG. 2B, several functional parts, having regard to the elasticity.
• These functional parts are located along the longitudinal direc ⁇ tion of the doctor blade 2. These functional parts are functionally substantially independent of each other. This means that a functional part of the elastically deformable member 4 can react to a stress due in particular to the unevenness of the surface to be printed without substantially affecting the functional part adjacent to the elastically deformable member 4.
• the elastically deformable member 4 has passages, openings, perforations, spacings, slots or the like piercings 16 above the lip 5 allowing the passage of excess printing ink.
• the elastically deformable member (s) 4 have a different linear mass from that of the lip 5. It follows that the elastically deformable member 4 has a vibra ⁇ tion period which is very different from that of the lip 5.
• the com ⁇ pairing of the lip 5 and of the elastic member (s) deformable 4 is therefore not likely to resonate at least substantially, and under the normal conditions of use of the doctor blade 2. In particular, this resonance is prevented or attenuated during the scraping of a support having the surface inequalities conventionally encountered.
• the elastically deformable member 4 is either separate from the head 3 and / or the lip 5, so as to be attached to the head 3, or it is an integral part of the head 3 and / or lip 5.
• the elastically deformable member 4 is associated with the head 3 and the lip 5 by being interposed between them. More precisely, the elastically deformable member 4 forms the single member or the main member by which the lip 5 is carried by the head 3.
• the elastically deformable member 4 is located transversely at least partially in extension of the head 3 and the lip 5.
• transverse direction is meant here a direction generally orthogonal to the longitudinal axis of doctor blade 2.
• the head 3 of the doctor blade 2 is rigidly fixed by the screw 10 in the vice constituted by jaws 9 of the doctor blade holder 1.
• the elastically deformable member 4 is formed by two struts or sheets struc ⁇ turally discontinuous in at least one place in the longitudinal direc ⁇ tion of the doctor blade 2 and constituting two combs which • extend along two sheets of springs spaced from one another.
• Such a ply is, generally, located between or outside but in the vicinity of the planes externally limiting the doctor blade 2.
• a ply, along which extends the elastically deformable member 4 is located substantially either in the middle zone between the two planes, or in the vicinity of at least one of the planes externally limiting the doctor blade 2.
• the elastically deformable members 4 also extend along several layers of springs spaced from one another, (visible in the profile views 3E to H).
• the turns or undulations of the member 4 are of triangular shape and come overlapping in the lip 5 to ensure flexible interdependence while they are an extension of the head 3.
• a double elastically deformable member 4 comprises pivoting elements 12, for example in the form of two wires arranged in a spiral or in undulation, which define with head 3 and lip 5 a deformable quadrilateral.
• This quadrilateral has four vertices, namely two vertices 21a, 21b in the head 3 and two vertices 22a, 22b in the lip 5.
• the vertices 21a and 22a are located on one side of the elastically deformable double member 4 and belong to the one of the wires, while the vertices 21b and 22b on the opposite opposite side belong to the other wire.
• a spring 11 connects the pivoting elements 12 diagonally.
• the vertices 21a, 21b, 22a, 22b form a trapezium whose large base is located on the side of the head 3, and the small base on the side of the lip 18.
• pressure is exerted on the head 3, there is a gain in the angle of the lip 5.
• the scraper lip comprises two parts, namely a core 23 fixed permanently to the base of the elastically deformable member 4, and an outer scraper part 24 of low linear mass, fixed to the core 23.
• This attachment is in this case of the removable type and by clipping.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Screen Printers (AREA)
• Manufacturing Of Printed Wiring (AREA)
• Printing Plates And Materials Therefor (AREA)
• Rotary Presses (AREA)
• Inking, Control Or Cleaning Of Printing Machines (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Cites Families (18)

• 1996
  • 1996-03-29 FR FR9604012A patent/FR2746704B1/fr not_active Expired - Fee Related
• 1997
  • 1997-04-01 JP JP9534938A patent/JP2000507514A/ja active Pending
  • 1997-04-01 DE DE69708070T patent/DE69708070T2/de not_active Expired - Fee Related
  • 1997-04-01 US US09/155,619 patent/US6109174A/en not_active Expired - Fee Related
  • 1997-04-01 EP EP97916420A patent/EP0889784B1/de not_active Expired - Lifetime
  • 1997-04-01 AU AU25076/97A patent/AU2507697A/en not_active Abandoned
  • 1997-04-01 WO PCT/EP1997/001628 patent/WO1997036747A1/fr active IP Right Grant
  • 1997-04-01 AT AT97916420T patent/ATE208267T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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